[PATCH v4 11/11] Use run_on_main_thread in gdb.post

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* [PATCH v4 11/11] Use run_on_main_thread in gdb.post_event
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (4 preceding siblings ...)
  2019-10-01 20:12 ` [PATCH v4 01/11] Use m4_include, not sinclude in .m4 files Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 07/11] Introduce run_on_main_thread Tom Tromey
                   ` (5 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This changes gdb.post_event to use the new run_on_main_thread
function.  This is somewhat tricky because the Python GIL must be held
while manipulating reference counts.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* python/python.c (class gdbpy_gil): New.
	(struct gdbpy_event): Add constructor, destructor, operator().
	(gdbpy_post_event): Use run_on_main_thread.
	(gdbpy_initialize_events): Remove.
	(do_start_initialization): Update.
---
 gdb/ChangeLog       |   8 +++
 gdb/python/python.c | 131 +++++++++++++++++++++-----------------------
 2 files changed, 70 insertions(+), 69 deletions(-)

diff --git a/gdb/python/python.c b/gdb/python/python.c
index ddf0e72d26f..1e054578900 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -28,7 +28,6 @@
 #include "value.h"
 #include "language.h"
 #include "event-loop.h"
-#include "serial.h"
 #include "readline/tilde.h"
 #include "python.h"
 #include "extension-priv.h"
@@ -940,63 +939,81 @@ gdbpy_source_script (const struct extension_language_defn *extlang,
 
 /* Posting and handling events.  */
 
+/* A helper class to save and restore the GIL, but without touching
+   the other globals that are handled by gdbpy_enter.  */
+
+class gdbpy_gil
+{
+public:
+
+  gdbpy_gil ()
+    : m_state (PyGILState_Ensure ())
+  {
+  }
+
+  ~gdbpy_gil ()
+  {
+    PyGILState_Release (m_state);
+  }
+
+  DISABLE_COPY_AND_ASSIGN (gdbpy_gil);
+
+private:
+
+  PyGILState_STATE m_state;
+};
+
 /* A single event.  */
 struct gdbpy_event
 {
-  /* The Python event.  This is just a callable object.  */
-  PyObject *event;
-  /* The next event.  */
-  struct gdbpy_event *next;
-};
+  gdbpy_event (gdbpy_ref<> &&func)
+    : m_func (func.release ())
+  {
+  }
 
-/* All pending events.  */
-static struct gdbpy_event *gdbpy_event_list;
-/* The final link of the event list.  */
-static struct gdbpy_event **gdbpy_event_list_end;
+  gdbpy_event (gdbpy_event &&other)
+    : m_func (other.m_func)
+  {
+    other.m_func = nullptr;
+  }
 
-/* So that we can wake up the main thread even when it is blocked in
-   poll().  */
-static struct serial_event *gdbpy_serial_event;
+  gdbpy_event (const gdbpy_event &other)
+    : m_func (other.m_func)
+  {
+    gdbpy_gil gil;
+    Py_XINCREF (m_func);
+  }
 
-/* The file handler callback.  This reads from the internal pipe, and
-   then processes the Python event queue.  This will always be run in
-   the main gdb thread.  */
+  ~gdbpy_event ()
+  {
+    gdbpy_gil gil;
+    Py_XDECREF (m_func);
+  }
 
-static void
-gdbpy_run_events (int error, gdb_client_data client_data)
-{
-  gdbpy_enter enter_py (get_current_arch (), current_language);
+  gdbpy_event &operator= (const gdbpy_event &other) = delete;
 
-  /* Clear the event fd.  Do this before flushing the events list, so
-     that any new event post afterwards is sure to re-awake the event
-     loop.  */
-  serial_event_clear (gdbpy_serial_event);
+  void operator() ()
+  {
+    gdbpy_enter enter_py (get_current_arch (), current_language);
 
-  while (gdbpy_event_list)
-    {
-      /* Dispatching the event might push a new element onto the event
-	 loop, so we update here "atomically enough".  */
-      struct gdbpy_event *item = gdbpy_event_list;
-      gdbpy_event_list = gdbpy_event_list->next;
-      if (gdbpy_event_list == NULL)
-	gdbpy_event_list_end = &gdbpy_event_list;
-
-      gdbpy_ref<> call_result (PyObject_CallObject (item->event, NULL));
-      if (call_result == NULL)
-	gdbpy_print_stack ();
+    gdbpy_ref<> call_result (PyObject_CallObject (m_func, NULL));
+    if (call_result == NULL)
+      gdbpy_print_stack ();
+  }
 
-      Py_DECREF (item->event);
-      xfree (item);
-    }
-}
+private:
+
+  /* The Python event.  This is just a callable object.  Note that
+     this is not a gdbpy_ref<>, because we have to take particular
+     care to only destroy the reference when holding the GIL. */
+  PyObject *m_func;
+};
 
 /* Submit an event to the gdb thread.  */
 static PyObject *
 gdbpy_post_event (PyObject *self, PyObject *args)
 {
-  struct gdbpy_event *event;
   PyObject *func;
-  int wakeup;
 
   if (!PyArg_ParseTuple (args, "O", &func))
     return NULL;
@@ -1010,36 +1027,13 @@ gdbpy_post_event (PyObject *self, PyObject *args)
 
   Py_INCREF (func);
 
-  /* From here until the end of the function, we have the GIL, so we
-     can operate on our global data structures without worrying.  */
-  wakeup = gdbpy_event_list == NULL;
-
-  event = XNEW (struct gdbpy_event);
-  event->event = func;
-  event->next = NULL;
-  *gdbpy_event_list_end = event;
-  gdbpy_event_list_end = &event->next;
-
-  /* Wake up gdb when needed.  */
-  if (wakeup)
-    serial_event_set (gdbpy_serial_event);
+  gdbpy_ref<> func_ref = gdbpy_ref<>::new_reference (func);
+  gdbpy_event event (std::move (func_ref));
+  run_on_main_thread (event);
 
   Py_RETURN_NONE;
 }
 
-/* Initialize the Python event handler.  */
-static int
-gdbpy_initialize_events (void)
-{
-  gdbpy_event_list_end = &gdbpy_event_list;
-
-  gdbpy_serial_event = make_serial_event ();
-  add_file_handler (serial_event_fd (gdbpy_serial_event),
-		    gdbpy_run_events, NULL);
-
-  return 0;
-}
-
 \f
 
 /* This is the extension_language_ops.before_prompt "method".  */
@@ -1704,7 +1698,6 @@ do_start_initialization ()
       || gdbpy_initialize_linetable () < 0
       || gdbpy_initialize_thread () < 0
       || gdbpy_initialize_inferior () < 0
-      || gdbpy_initialize_events () < 0
       || gdbpy_initialize_eventregistry () < 0
       || gdbpy_initialize_py_events () < 0
       || gdbpy_initialize_event () < 0
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 04/11] Add RAII class for blocking gdb signals
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 10/11] Add maint set/show max-worker-threads Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 09/11] Demangle minsyms in parallel Tom Tromey
                   ` (9 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This adds configury support and an RAII class that can be used to
temporarily block signals that are used by gdb.  (This class is not
used in this patch, but it split out for easier review.)

The idea of this patch is that these signals should only be delivered
to the main thread.  So, when creating a background thread, they are
temporarily blocked; the blocked state is inherited by the new thread.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* gdbsupport/common.m4 (GDB_AC_COMMON): Check for
	pthread_sigmask.
	* configure: Rebuild.
	* gdbsupport/block-signals.h: New file.

gdb/gdbserver/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.
---
 gdb/ChangeLog                  |   7 ++
 gdb/configure                  |  82 +++++++++++++++++++++
 gdb/gdbserver/ChangeLog        |   4 ++
 gdb/gdbserver/configure        | 128 +++++++++++++++++++++++++++++++++
 gdb/gdbsupport/block-signals.h |  65 +++++++++++++++++
 gdb/gdbsupport/common.m4       |   5 ++
 6 files changed, 291 insertions(+)
 create mode 100644 gdb/gdbsupport/block-signals.h

diff --git a/gdb/configure b/gdb/configure
index 263f301d8ee..0235c3e8c12 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -2506,6 +2506,73 @@ fi
   as_fn_set_status $ac_retval
 
 } # ac_fn_cxx_try_link
+
+# ac_fn_cxx_check_func LINENO FUNC VAR
+# ------------------------------------
+# Tests whether FUNC exists, setting the cache variable VAR accordingly
+ac_fn_cxx_check_func ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $2" >&5
+$as_echo_n "checking for $2... " >&6; }
+if eval \${$3+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Define $2 to an innocuous variant, in case <limits.h> declares $2.
+   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
+#define $2 innocuous_$2
+
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $2 (); below.
+    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+    <limits.h> exists even on freestanding compilers.  */
+
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+
+#undef $2
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char $2 ();
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined __stub_$2 || defined __stub___$2
+choke me
+#endif
+
+int
+main ()
+{
+return $2 ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+  eval "$3=yes"
+else
+  eval "$3=no"
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+eval ac_res=\$$3
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_cxx_check_func
 cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
@@ -14316,6 +14383,21 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $gdb_cv_cxx_std_thread" >&5
 $as_echo "$gdb_cv_cxx_std_thread" >&6; }
+
+    # This check must be here, while LIBS includes any necessary
+    # threading library.
+    for ac_func in pthread_sigmask
+do :
+  ac_fn_cxx_check_func "$LINENO" "pthread_sigmask" "ac_cv_func_pthread_sigmask"
+if test "x$ac_cv_func_pthread_sigmask" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PTHREAD_SIGMASK 1
+_ACEOF
+
+fi
+done
+
+
     LIBS="$save_LIBS"
     CXXFLAGS="$save_CXXFLAGS"
   fi
diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
index aa13ce6aa4b..53243990097 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -1972,6 +1972,119 @@ $as_echo "$ac_res" >&6; }
 
 } # ac_fn_c_check_decl
 
+# ac_fn_cxx_try_link LINENO
+# -------------------------
+# Try to link conftest.$ac_ext, and return whether this succeeded.
+ac_fn_cxx_try_link ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  rm -f conftest.$ac_objext conftest$ac_exeext
+  if { { ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+$as_echo "$ac_try_echo"; } >&5
+  (eval "$ac_link") 2>conftest.err
+  ac_status=$?
+  if test -s conftest.err; then
+    grep -v '^ *+' conftest.err >conftest.er1
+    cat conftest.er1 >&5
+    mv -f conftest.er1 conftest.err
+  fi
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; } && {
+	 test -z "$ac_cxx_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest$ac_exeext && {
+	 test "$cross_compiling" = yes ||
+	 test -x conftest$ac_exeext
+       }; then :
+  ac_retval=0
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	ac_retval=1
+fi
+  # Delete the IPA/IPO (Inter Procedural Analysis/Optimization) information
+  # created by the PGI compiler (conftest_ipa8_conftest.oo), as it would
+  # interfere with the next link command; also delete a directory that is
+  # left behind by Apple's compiler.  We do this before executing the actions.
+  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+  as_fn_set_status $ac_retval
+
+} # ac_fn_cxx_try_link
+
+# ac_fn_cxx_check_func LINENO FUNC VAR
+# ------------------------------------
+# Tests whether FUNC exists, setting the cache variable VAR accordingly
+ac_fn_cxx_check_func ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $2" >&5
+$as_echo_n "checking for $2... " >&6; }
+if eval \${$3+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Define $2 to an innocuous variant, in case <limits.h> declares $2.
+   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
+#define $2 innocuous_$2
+
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $2 (); below.
+    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+    <limits.h> exists even on freestanding compilers.  */
+
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+
+#undef $2
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char $2 ();
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined __stub_$2 || defined __stub___$2
+choke me
+#endif
+
+int
+main ()
+{
+return $2 ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+  eval "$3=yes"
+else
+  eval "$3=no"
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+eval ac_res=\$$3
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_cxx_check_func
+
 # ac_fn_c_compute_int LINENO EXPR VAR INCLUDES
 # --------------------------------------------
 # Tries to find the compile-time value of EXPR in a program that includes
@@ -7608,6 +7721,21 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $gdb_cv_cxx_std_thread" >&5
 $as_echo "$gdb_cv_cxx_std_thread" >&6; }
+
+    # This check must be here, while LIBS includes any necessary
+    # threading library.
+    for ac_func in pthread_sigmask
+do :
+  ac_fn_cxx_check_func "$LINENO" "pthread_sigmask" "ac_cv_func_pthread_sigmask"
+if test "x$ac_cv_func_pthread_sigmask" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PTHREAD_SIGMASK 1
+_ACEOF
+
+fi
+done
+
+
     LIBS="$save_LIBS"
     CXXFLAGS="$save_CXXFLAGS"
   fi
diff --git a/gdb/gdbsupport/block-signals.h b/gdb/gdbsupport/block-signals.h
new file mode 100644
index 00000000000..04a53a2ec14
--- /dev/null
+++ b/gdb/gdbsupport/block-signals.h
@@ -0,0 +1,65 @@
+/* Block signals used by gdb
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_BLOCK_SIGNALS_H
+#define GDBSUPPORT_BLOCK_SIGNALS_H
+
+#include <signal.h>
+
+namespace gdb
+{
+
+/* This is an RAII class that temporarily blocks the signals needed by
+   gdb.  This can be used before starting a new thread to ensure that
+   this thread starts with the appropriate signals blocked.  */
+class block_signals
+{
+public:
+  block_signals ()
+  {
+#ifdef HAVE_PTHREAD_SIGMASK
+    sigset_t mask;
+    sigemptyset (&mask);
+    sigaddset (&mask, SIGINT);
+    sigaddset (&mask, SIGCHLD);
+    sigaddset (&mask, SIGALRM);
+    sigaddset (&mask, SIGWINCH);
+    pthread_sigmask (SIG_BLOCK, &mask, &m_old_mask);
+#endif
+  }
+
+  ~block_signals ()
+  {
+#ifdef HAVE_PTHREAD_SIGMASK
+    pthread_sigmask (SIG_SETMASK, &m_old_mask, nullptr);
+#endif
+  }
+
+  DISABLE_COPY_AND_ASSIGN (block_signals);
+
+private:
+
+#ifdef HAVE_PTHREAD_SIGMASK
+  sigset_t m_old_mask;
+#endif
+};
+
+}
+
+#endif /* GDBSUPPORT_BLOCK_SIGNALS_H */
diff --git a/gdb/gdbsupport/common.m4 b/gdb/gdbsupport/common.m4
index 0f0e9a866eb..b5f477b0769 100644
--- a/gdb/gdbsupport/common.m4
+++ b/gdb/gdbsupport/common.m4
@@ -53,6 +53,11 @@ AC_DEFUN([GDB_AC_COMMON], [
     [[std::thread t(callback);]])],
 				  gdb_cv_cxx_std_thread=yes,
 				  gdb_cv_cxx_std_thread=no)])
+
+    # This check must be here, while LIBS includes any necessary
+    # threading library.
+    AC_CHECK_FUNCS([pthread_sigmask])
+
     LIBS="$save_LIBS"
     CXXFLAGS="$save_CXXFLAGS"
   fi
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 10/11] Add maint set/show max-worker-threads
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-02 14:54   ` Eli Zaretskii
  2019-10-01 20:12 ` [PATCH v4 04/11] Add RAII class for blocking gdb signals Tom Tromey
                   ` (10 subsequent siblings)
  11 siblings, 1 reply; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This adds maint commands to control the maximum number of worker
threads that gdb can use.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* NEWS: Add entry.
	* maint.c (_initialize_maint_cmds): Add "max-worker-threads" maint
	commands.

gdb/doc/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* gdb.texinfo (Maintenance Commands): Document new maint
	commands.
---
 gdb/ChangeLog       |  6 ++++++
 gdb/NEWS            |  6 ++++++
 gdb/doc/ChangeLog   |  5 +++++
 gdb/doc/gdb.texinfo | 14 ++++++++++++++
 gdb/maint.c         | 12 ++++++++++++
 5 files changed, 43 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index 779fd91d3a6..7d4988f6cb0 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -122,6 +122,12 @@ set style highlight background COLOR
 set style highlight intensity VALUE
   Control the styling of highlightings.
 
+maint set max-worker-threads
+maint show max-worker-threads
+  Control the maximum number of worker threads that can be used by GDB.
+  The default is "unlimited".  Currently worker threads are only used when
+  demangling the names of linker symbols.
+
 maint set test-settings KIND
 maint show test-settings KIND
   A set of commands used by the testsuite for exercising the settings
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index f2713c03960..04a40091de4 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -37663,6 +37663,20 @@ with the DWARF frame unwinders enabled.
 
 If DWARF frame unwinders are not supported for a particular target
 architecture, then enabling this flag does not cause them to be used.
+
+@kindex maint set max-worker-threads
+@kindex maint show max-worker-threads
+@item maint set max-worker-threads
+@item maint show max-worker-threads
+Control the number of worker threads that may be used by @value{GDBN}.
+On capable hosts, @value{GDBN} may use multiple threads to speed up
+certain CPU-intensive operations, such as demangling symbol names.
+While the number of threads used by @value{GDBN} may vary, this
+command can be used to set an upper bound on this number.  The default
+is @code{unlimited}.  Note that this only controls worker threads
+started by @value{GDBN} itself; libraries used by @value{GDBN} may
+start threads of their own.
+
 @kindex maint set profile
 @kindex maint show profile
 @cindex profiling GDB
diff --git a/gdb/maint.c b/gdb/maint.c
index ec9f4abb264..8428bea4f92 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -40,6 +40,7 @@
 #include "top.h"
 #include "maint.h"
 #include "gdbsupport/selftest.h"
+#include "gdbsupport/parallel-for.h"
 
 #include "cli/cli-decode.h"
 #include "cli/cli-utils.h"
@@ -1312,4 +1313,15 @@ When enabled GDB is profiled."),
 			   show_maintenance_profile_p,
 			   &maintenance_set_cmdlist,
 			   &maintenance_show_cmdlist);
+
+  add_setshow_zuinteger_unlimited_cmd ("max-worker-threads",
+				       class_maintenance,
+				       &gdb::max_threads, _("\
+Set the maximum number of worker threads GDB can use."), _("\
+Set the maximum number of worker threads GDB can use."), _("\
+GDB may use multiple threads to speed up certain CPU-intensive operations,\n\
+such as demangling symbol names."),
+				       NULL, NULL,
+				       &maintenance_set_cmdlist,
+				       &maintenance_show_cmdlist);
 }
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 07/11] Introduce run_on_main_thread
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (5 preceding siblings ...)
  2019-10-01 20:12 ` [PATCH v4 11/11] Use run_on_main_thread in gdb.post_event Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 05/11] Introduce alternate_signal_stack RAII class Tom Tromey
                   ` (4 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This introduces a way for a callback to be run on the main thread.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* unittests/main-thread-selftests.c: New file.
	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add
	main-thread-selftests.c.
	* ser-event.h (run_on_main_thread): Declare.
	* ser-event.c (runnable_event, runnables, runnable_mutex): New
	globals.
	(run_events, run_on_main_thread, _initialize_ser_event): New
	functions.
---
 gdb/ChangeLog                         | 11 ++++
 gdb/Makefile.in                       |  1 +
 gdb/ser-event.c                       | 78 ++++++++++++++++++++++++++
 gdb/ser-event.h                       |  6 ++
 gdb/unittests/main-thread-selftests.c | 80 +++++++++++++++++++++++++++
 5 files changed, 176 insertions(+)
 create mode 100644 gdb/unittests/main-thread-selftests.c

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index c4c858b5594..d4eca61d06e 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -426,6 +426,7 @@ SUBDIR_UNITTESTS_SRCS = \
 	unittests/optional-selftests.c \
 	unittests/parse-connection-spec-selftests.c \
 	unittests/ptid-selftests.c \
+	unittests/main-thread-selftests.c \
 	unittests/mkdir-recursive-selftests.c \
 	unittests/rsp-low-selftests.c \
 	unittests/scoped_fd-selftests.c \
diff --git a/gdb/ser-event.c b/gdb/ser-event.c
index a65a186526f..029ced7619c 100644
--- a/gdb/ser-event.c
+++ b/gdb/ser-event.c
@@ -20,6 +20,10 @@
 #include "ser-event.h"
 #include "serial.h"
 #include "gdbsupport/filestuff.h"
+#if CXX_STD_THREAD
+#include <mutex>
+#endif
+#include "event-loop.h"
 
 /* On POSIX hosts, a serial_event is basically an abstraction for the
    classical self-pipe trick.
@@ -217,3 +221,77 @@ serial_event_clear (struct serial_event *event)
   ResetEvent (state->event);
 #endif
 }
+
+\f
+
+/* The serial event used when posting runnables.  */
+
+static struct serial_event *runnable_event;
+
+/* Runnables that have been posted.  */
+
+static std::vector<std::function<void ()>> runnables;
+
+#if CXX_STD_THREAD
+
+/* Mutex to hold when handling runnable_event or runnables.  */
+
+static std::mutex runnable_mutex;
+
+#endif
+
+/* Run all the queued runnables.  */
+
+static void
+run_events (int error, gdb_client_data client_data)
+{
+  std::vector<std::function<void ()>> local;
+
+  /* Hold the lock while changing the globals, but not while running
+     the runnables.  */
+  {
+#if CXX_STD_THREAD
+    std::lock_guard<std::mutex> lock (runnable_mutex);
+#endif
+
+    /* Clear the event fd.  Do this before flushing the events list,
+       so that any new event post afterwards is sure to re-awaken the
+       event loop.  */
+    serial_event_clear (runnable_event);
+
+    /* Move the vector in case running a runnable pushes a new
+       runnable.  */
+    local = std::move (runnables);
+  }
+
+  for (auto &item : local)
+    {
+      try
+	{
+	  item ();
+	}
+      catch (...)
+	{
+	  /* Ignore exceptions in the callback.  */
+	}
+    }
+}
+
+/* See ser-event.h.  */
+
+void
+run_on_main_thread (std::function<void ()> &&func)
+{
+#if CXX_STD_THREAD
+  std::lock_guard<std::mutex> lock (runnable_mutex);
+#endif
+  runnables.emplace_back (std::move (func));
+  serial_event_set (runnable_event);
+}
+
+void
+_initialize_ser_event ()
+{
+  runnable_event = make_serial_event ();
+  add_file_handler (serial_event_fd (runnable_event), run_events, nullptr);
+}
diff --git a/gdb/ser-event.h b/gdb/ser-event.h
index 137348557f9..61a84f9cc79 100644
--- a/gdb/ser-event.h
+++ b/gdb/ser-event.h
@@ -19,6 +19,8 @@
 #ifndef SER_EVENT_H
 #define SER_EVENT_H
 
+#include <functional>
+
 /* This is used to be able to signal the event loop (or any other
    select/poll) of events, in a race-free manner.
 
@@ -48,4 +50,8 @@ extern void serial_event_set (struct serial_event *event);
    call is made.  */
 extern void serial_event_clear (struct serial_event *event);
 
+/* Send a runnable to the main thread.  */
+
+extern void run_on_main_thread (std::function<void ()> &&);
+
 #endif
diff --git a/gdb/unittests/main-thread-selftests.c b/gdb/unittests/main-thread-selftests.c
new file mode 100644
index 00000000000..e5bd2d36cea
--- /dev/null
+++ b/gdb/unittests/main-thread-selftests.c
@@ -0,0 +1,80 @@
+/* Self tests for run_on_main_thread
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "gdbsupport/selftest.h"
+#include "gdbsupport/block-signals.h"
+#include "ser-event.h"
+#include "event-loop.h"
+#if CXX_STD_THREAD
+#include <thread>
+#endif
+
+namespace selftests {
+namespace main_thread_tests {
+
+#if CXX_STD_THREAD
+
+static bool done;
+
+static void
+set_done ()
+{
+  run_on_main_thread ([] ()
+    {
+      done = true;
+    });
+}
+
+static void
+run_tests ()
+{
+  std::thread thread;
+
+  done = false;
+
+  {
+    gdb::block_signals blocker;
+
+    thread = std::thread (set_done);
+  }
+
+  while (!done && gdb_do_one_event () >= 0)
+    ;
+
+  /* Actually the test will just hang, but we want to test
+     something.  */
+  SELF_CHECK (done);
+
+  thread.join ();
+}
+
+#endif
+
+}
+}
+
+void
+_initialize_main_thread_selftests ()
+{
+#if CXX_STD_THREAD
+  selftests::register_test ("main_thread",
+			    selftests::main_thread_tests::run_tests);
+#endif
+}
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 09/11] Demangle minsyms in parallel
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 10/11] Add maint set/show max-worker-threads Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 04/11] Add RAII class for blocking gdb signals Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 08/11] Introduce thread-safe way to handle SIGSEGV Tom Tromey
                   ` (8 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This patch introduces a simple parallel for_each and changes the
minimal symbol reader to use it when computing the demangled name for
a minimal symbol.  This yields a speedup when reading minimal symbols.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* minsyms.c (minimal_symbol_reader::install): Use
	parallel_for_each.
	* gdbsupport/parallel-for.h: New file.
	* gdbsupport/parallel-for.c: New file.
	* Makefile.in (HFILES_NO_SRCDIR): Add gdbsupport/parallel-for.h.
	(COMMON_SFILES): Add gdbsupport/parallel-for.c.
---
 gdb/ChangeLog                 |   9 +++
 gdb/Makefile.in               |   2 +
 gdb/gdbsupport/parallel-for.c |  27 +++++++++
 gdb/gdbsupport/parallel-for.h | 101 ++++++++++++++++++++++++++++++++++
 gdb/minsyms.c                 |  31 +++++++----
 5 files changed, 160 insertions(+), 10 deletions(-)
 create mode 100644 gdb/gdbsupport/parallel-for.c
 create mode 100644 gdb/gdbsupport/parallel-for.h

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index d4eca61d06e..c7b9efdbbc6 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -970,6 +970,7 @@ COMMON_SFILES = \
 	gdbsupport/gdb_vecs.c \
 	gdbsupport/netstuff.c \
 	gdbsupport/new-op.c \
+	gdbsupport/parallel-for.c \
 	gdbsupport/pathstuff.c \
 	gdbsupport/print-utils.c \
 	gdbsupport/ptid.c \
@@ -1469,6 +1470,7 @@ HFILES_NO_SRCDIR = \
 	gdbsupport/common-inferior.h \
 	gdbsupport/netstuff.h \
 	gdbsupport/host-defs.h \
+	gdbsupport/parallel-for.h \
 	gdbsupport/pathstuff.h \
 	gdbsupport/print-utils.h \
 	gdbsupport/ptid.h \
diff --git a/gdb/gdbsupport/parallel-for.c b/gdb/gdbsupport/parallel-for.c
new file mode 100644
index 00000000000..0024278bd7f
--- /dev/null
+++ b/gdb/gdbsupport/parallel-for.c
@@ -0,0 +1,27 @@
+/* Parallel for loops
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "gdbsupport/common-defs.h"
+#include "gdbsupport/parallel-for.h"
+
+namespace gdb
+{
+/* See parallel-for.h.  */
+int max_threads = -1;
+}
diff --git a/gdb/gdbsupport/parallel-for.h b/gdb/gdbsupport/parallel-for.h
new file mode 100644
index 00000000000..60b9472e1fe
--- /dev/null
+++ b/gdb/gdbsupport/parallel-for.h
@@ -0,0 +1,101 @@
+/* Parallel for loops
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_PARALLEL_FOR_H
+#define GDBSUPPORT_PARALLEL_FOR_H
+
+#include <algorithm>
+#if CXX_STD_THREAD
+#include <system_error>
+#include <thread>
+#endif
+
+#include "gdbsupport/block-signals.h"
+
+namespace gdb
+{
+
+/* True if threading should be enabled.  */
+
+extern int max_threads;
+
+/* A very simple "parallel for".  This splits the range of iterators
+   into subranges, and then passes each subrange to the callback.  The
+   work may or may not be done in separate threads.
+
+   This approach was chosen over having the callback work on single
+   items because it makes it simple for the caller to do
+   once-per-subrange initialization and destruction.  */
+
+template<class RandomIt, class RangeFunction>
+void
+parallel_for_each (RandomIt first, RandomIt last, RangeFunction callback)
+{
+#if CXX_STD_THREAD
+  int n_threads = std::thread::hardware_concurrency ();
+  /* So we can use a local array below.  */
+  const int local_max = 16;
+  /* Be sure to handle the "unlimited" case.  */
+  if (max_threads >= 0 && n_threads > max_threads)
+    n_threads = max_threads;
+  if (n_threads > local_max)
+    n_threads = local_max;
+  int n_actual_threads = 0;
+
+  std::thread threads[local_max];
+  size_t n_elements = last - first;
+  if (n_threads > 1 && 2 * n_threads <= n_elements)
+    {
+      /* Ensure that signals used by gdb are blocked in the new
+	 threads.  */
+      block_signals blocker;
+
+      size_t elts_per_thread = n_elements / n_threads;
+      n_actual_threads = n_threads - 1;
+      for (int i = 0; i < n_actual_threads; ++i)
+	{
+	  RandomIt end = first + elts_per_thread;
+	  try
+	    {
+	      threads[i] = std::thread (callback, first, end);
+	    }
+	  catch (const std::system_error &failure)
+	    {
+	      /* If a thread failed to start, ignore it and fall back
+		 to processing in the main thread. */
+	      n_actual_threads = i;
+	      break;
+	    }
+	  first = end;
+	}
+    }
+#endif /* CXX_STD_THREAD */
+
+  /* Process all the remaining elements in the main thread.  */
+  callback (first, last);
+
+#if CXX_STD_THREAD
+  for (int i = 0; i < n_actual_threads; ++i)
+    threads[i].join ();
+#endif /* CXX_STD_THREAD */
+}
+
+}
+
+#endif /* GDBSUPPORT_PARALLEL_FOR_H */
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 2b259d39c11..84bf2bb61e2 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -53,6 +53,8 @@
 #include "gdbsupport/symbol.h"
 #include <algorithm>
 #include "safe-ctype.h"
+#include "gdbsupport/alt-stack.h"
+#include "gdbsupport/parallel-for.h"
 
 /* See minsyms.h.  */
 
@@ -1332,16 +1334,25 @@ minimal_symbol_reader::install ()
       m_objfile->per_bfd->msymbols = std::move (msym_holder);
 
       msymbols = m_objfile->per_bfd->msymbols.get ();
-      for (int i = 0; i < mcount; ++i)
-	{
-	  if (!msymbols[i].name_set)
-	    {
-	      symbol_set_names (&msymbols[i], msymbols[i].name,
-				strlen (msymbols[i].name), 0,
-				m_objfile->per_bfd);
-	      msymbols[i].name_set = 1;
-	    }
-	}
+      gdb::parallel_for_each
+	(&msymbols[0], &msymbols[mcount],
+	 [&] (minimal_symbol *start, minimal_symbol *end)
+	 {
+	   /* Ensure that SIGSEGV is delivered to an alternate signal
+	      stack.  */
+	   gdb::alternate_signal_stack signal_stack;
+
+	   for (minimal_symbol *msym = start; msym < end; ++msym)
+	     {
+	       if (!msym->name_set)
+		 {
+		   symbol_set_names (msym, msym->name,
+				     strlen (msym->name), 0,
+				     m_objfile->per_bfd);
+		   msym->name_set = 1;
+		 }
+	     }
+	 });
 
       build_minimal_symbol_hash_tables (m_objfile);
     }
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 05/11] Introduce alternate_signal_stack RAII class
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (6 preceding siblings ...)
  2019-10-01 20:12 ` [PATCH v4 07/11] Introduce run_on_main_thread Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 03/11] Add configure check for std::thread Tom Tromey
                   ` (3 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This introduces a new RAII class that temporarily installs an
alternate signal stack (on systems that have sigaltstack); then
changes the one gdb use of sigaltstack to use this class instead.

This will be used in a later patch, when creating new threads that may
want to handle SIGSEGV.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* main.c (setup_alternate_signal_stack): Remove.
	(captured_main_1): Use gdb::alternate_signal_stack.
	* gdbsupport/alt-stack.h: New file.
---
 gdb/ChangeLog              |  6 ++++
 gdb/gdbsupport/alt-stack.h | 70 ++++++++++++++++++++++++++++++++++++++
 gdb/main.c                 | 26 ++------------
 3 files changed, 78 insertions(+), 24 deletions(-)
 create mode 100644 gdb/gdbsupport/alt-stack.h

diff --git a/gdb/gdbsupport/alt-stack.h b/gdb/gdbsupport/alt-stack.h
new file mode 100644
index 00000000000..1708fb4ce92
--- /dev/null
+++ b/gdb/gdbsupport/alt-stack.h
@@ -0,0 +1,70 @@
+/* Temporarily install an alternate signal stack
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_ALT_STACK_H
+#define GDBSUPPORT_ALT_STACK_H
+
+#include <signal.h>
+
+namespace gdb
+{
+
+/* Try to set up an alternate signal stack for SIGSEGV handlers.
+   This allows us to handle SIGSEGV signals generated when the
+   normal process stack is exhausted.  If this stack is not set
+   up (sigaltstack is unavailable or fails) and a SIGSEGV is
+   generated when the normal stack is exhausted then the program
+   will behave as though no SIGSEGV handler was installed.  */
+class alternate_signal_stack
+{
+public:
+  alternate_signal_stack ()
+  {
+#ifdef HAVE_SIGALTSTACK
+    m_stack.reset ((char *) xmalloc (SIGSTKSZ));
+
+    stack_t stack;
+    stack.ss_sp = m_stack.get ();
+    stack.ss_size = SIGSTKSZ;
+    stack.ss_flags = 0;
+
+    sigaltstack (&stack, &m_old_stack);
+#endif
+  }
+
+  ~alternate_signal_stack ()
+  {
+#ifdef HAVE_SIGALTSTACK
+    sigaltstack (&m_old_stack, nullptr);
+#endif
+  }
+
+  DISABLE_COPY_AND_ASSIGN (alternate_signal_stack);
+
+private:
+
+#ifdef HAVE_SIGALTSTACK
+  gdb::unique_xmalloc_ptr<char> m_stack;
+  stack_t m_old_stack;
+#endif
+};
+
+}
+
+#endif /* GDBSUPPORT_ALT_STACK_H */
diff --git a/gdb/main.c b/gdb/main.c
index 14d9e796538..5f6e8bec86e 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -48,6 +48,7 @@
 #include <vector>
 #include "gdbsupport/pathstuff.h"
 #include "cli/cli-style.h"
+#include "gdbsupport/alt-stack.h"
 
 /* The selected interpreter.  This will be used as a set command
    variable, so it should always be malloc'ed - since
@@ -289,29 +290,6 @@ get_init_files (std::string *system_gdbinit,
   *local_gdbinit = localinit;
 }
 
-/* Try to set up an alternate signal stack for SIGSEGV handlers.
-   This allows us to handle SIGSEGV signals generated when the
-   normal process stack is exhausted.  If this stack is not set
-   up (sigaltstack is unavailable or fails) and a SIGSEGV is
-   generated when the normal stack is exhausted then the program
-   will behave as though no SIGSEGV handler was installed.  */
-
-static void
-setup_alternate_signal_stack (void)
-{
-#ifdef HAVE_SIGALTSTACK
-  stack_t ss;
-
-  /* FreeBSD versions older than 11.0 use char * for ss_sp instead of
-     void *.  This cast works with both types.  */
-  ss.ss_sp = (char *) xmalloc (SIGSTKSZ);
-  ss.ss_size = SIGSTKSZ;
-  ss.ss_flags = 0;
-
-  sigaltstack(&ss, NULL);
-#endif
-}
-
 /* Call command_loop.  */
 
 /* Prevent inlining this function for the benefit of GDB's selftests
@@ -857,7 +835,7 @@ captured_main_1 (struct captured_main_args *context)
   save_original_signals_state (quiet);
 
   /* Try to set up an alternate signal stack for SIGSEGV handlers.  */
-  setup_alternate_signal_stack ();
+  gdb::alternate_signal_stack signal_stack;
 
   /* Initialize all files.  */
   gdb_init (gdb_program_name);
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 03/11] Add configure check for std::thread
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (7 preceding siblings ...)
  2019-10-01 20:12 ` [PATCH v4 05/11] Introduce alternate_signal_stack RAII class Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:16 ` [PATCH v4 02/11] Defer minimal symbol name-setting Tom Tromey
                   ` (2 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This adds a configure check for std::thread.  This is needed because
std::thread is not available on some systems, like some versions of
mingw and DJGPP.

This also adds configury to make sure that a threaded gdb links
against the correct threading library (-lpthread or the like), and
passes the right flags (e.g., -pthread) to the compilations.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* acinclude.m4: Include ax_pthread.m4.
	* Makefile.in (PTHREAD_CFLAGS, PTHREAD_LIBS): New variables.
	(INTERNAL_CFLAGS_BASE): Use PTHREAD_CFLAGS.
	(CLIBS): Use PTHREAD_LIBS.
	(aclocal_m4_deps): Add ax_pthread.m4.
	* config.in, configure: Rebuild.
	* gdbsupport/common.m4 (GDB_AC_COMMON): Check for std::thread.

gdb/gdbserver/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* acinclude.m4: Include ax_pthread.m4.
	* config.in, configure: Rebuild.
---
 gdb/ChangeLog              |  10 +
 gdb/Makefile.in            |  12 +-
 gdb/acinclude.m4           |   2 +
 gdb/config.in              |   3 +
 gdb/configure              | 767 +++++++++++++++++++++++++++++++++++++
 gdb/gdbserver/ChangeLog    |   5 +
 gdb/gdbserver/acinclude.m4 |   2 +
 gdb/gdbserver/config.in    |   3 +
 gdb/gdbserver/configure    | 767 +++++++++++++++++++++++++++++++++++++
 gdb/gdbsupport/common.m4   |  26 ++
 10 files changed, 1593 insertions(+), 4 deletions(-)

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index d6282636752..c4c858b5594 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -203,6 +203,9 @@ WERROR_CFLAGS = @WERROR_CFLAGS@
 GDB_WARN_CFLAGS = $(WARN_CFLAGS)
 GDB_WERROR_CFLAGS = $(WERROR_CFLAGS)
 
+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_LIBS = @PTHREAD_LIBS@
+
 RDYNAMIC = @RDYNAMIC@
 
 # Where is the INTL library?  Typically in ../intl.
@@ -569,7 +572,7 @@ INTERNAL_CFLAGS_BASE = \
 	$(GDB_CFLAGS) $(OPCODES_CFLAGS) $(READLINE_CFLAGS) $(ZLIBINC) \
 	$(BFD_CFLAGS) $(INCLUDE_CFLAGS) $(LIBDECNUMBER_CFLAGS) \
 	$(INTL_CFLAGS) $(INCGNU) $(ENABLE_CFLAGS) $(INTERNAL_CPPFLAGS) \
-	$(SRCHIGH_CFLAGS)
+	$(SRCHIGH_CFLAGS) $(PTHREAD_CFLAGS)
 INTERNAL_WARN_CFLAGS = $(INTERNAL_CFLAGS_BASE) $(GDB_WARN_CFLAGS)
 INTERNAL_CFLAGS = $(INTERNAL_WARN_CFLAGS) $(GDB_WERROR_CFLAGS)
 
@@ -583,7 +586,7 @@ LDFLAGS = @LDFLAGS@
 # PROFILE_CFLAGS is _not_ included, however, because we use monstartup.
 INTERNAL_LDFLAGS = \
 	$(CXXFLAGS) $(GLOBAL_CFLAGS) $(MH_LDFLAGS) \
-	$(LDFLAGS) $(CONFIG_LDFLAGS)
+	$(LDFLAGS) $(CONFIG_LDFLAGS) $(PTHREAD_CFLAGS)
 
 # Libraries and corresponding dependencies for compiling gdb.
 # XM_CLIBS, defined in *config files, have host-dependent libs.
@@ -593,7 +596,7 @@ CLIBS = $(SIM) $(READLINE) $(OPCODES) $(BFD) $(ZLIB) $(INTL) $(LIBIBERTY) $(LIBD
 	@LIBS@ @GUILE_LIBS@ @PYTHON_LIBS@ \
 	$(LIBEXPAT) $(LIBLZMA) $(LIBBABELTRACE) $(LIBIPT) \
 	$(LIBIBERTY) $(WIN32LIBS) $(LIBGNU) $(LIBICONV) $(LIBMPFR) \
-	$(SRCHIGH_LIBS)
+	$(SRCHIGH_LIBS) $(PTHREAD_LIBS)
 CDEPS = $(NAT_CDEPS) $(SIM) $(BFD) $(READLINE_DEPS) \
 	$(OPCODES) $(INTL_DEPS) $(LIBIBERTY) $(CONFIG_DEPS) $(LIBGNU)
 
@@ -2054,7 +2057,8 @@ aclocal_m4_deps = \
 	../config/depstand.m4 \
 	../config/lcmessage.m4 \
 	../config/codeset.m4 \
-	../config/zlib.m4
+	../config/zlib.m4 \
+	../config/ax_pthread.m4
 
 $(srcdir)/aclocal.m4: @MAINTAINER_MODE_TRUE@ $(aclocal_m4_deps)
 	cd $(srcdir) && $(ACLOCAL) $(ACLOCAL_AMFLAGS)
diff --git a/gdb/acinclude.m4 b/gdb/acinclude.m4
index 5f1358b8207..8592b6c875b 100644
--- a/gdb/acinclude.m4
+++ b/gdb/acinclude.m4
@@ -73,6 +73,8 @@ m4_include(ptrace.m4)
 
 m4_include(ax_cxx_compile_stdcxx.m4)
 
+m4_include([../config/ax_pthread.m4])
+
 ## ----------------------------------------- ##
 ## ANSIfy the C compiler whenever possible.  ##
 ## From Franc,ois Pinard                     ##
diff --git a/gdb/config.in b/gdb/config.in
index 26ca02f6a3e..2f17cb3f8a4 100644
--- a/gdb/config.in
+++ b/gdb/config.in
@@ -17,6 +17,9 @@
    */
 #undef CRAY_STACKSEG_END
 
+/* Define to 1 if std::thread works. */
+#undef CXX_STD_THREAD
+
 /* Define to 1 if using `alloca.c'. */
 #undef C_ALLOCA
 
diff --git a/gdb/configure b/gdb/configure
index 22a5f6051d4..263f301d8ee 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -697,6 +697,11 @@ SYSTEM_GDBINIT
 TARGET_SYSTEM_ROOT
 CONFIG_LDFLAGS
 RDYNAMIC
+PTHREAD_CFLAGS
+PTHREAD_LIBS
+PTHREAD_CC
+ax_pthread_config
+SED
 ALLOCA
 LTLIBIPT
 LIBIPT
@@ -13180,6 +13185,75 @@ _ACEOF
 
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for a sed that does not truncate output" >&5
+$as_echo_n "checking for a sed that does not truncate output... " >&6; }
+if ${ac_cv_path_SED+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+            ac_script=s/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/
+     for ac_i in 1 2 3 4 5 6 7; do
+       ac_script="$ac_script$as_nl$ac_script"
+     done
+     echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
+     { ac_script=; unset ac_script;}
+     if test -z "$SED"; then
+  ac_path_SED_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in sed gsed; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_SED="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_SED" || continue
+# Check for GNU ac_path_SED and select it if it is found.
+  # Check for GNU $ac_path_SED
+case `"$ac_path_SED" --version 2>&1` in
+*GNU*)
+  ac_cv_path_SED="$ac_path_SED" ac_path_SED_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo '' >> "conftest.nl"
+    "$ac_path_SED" -f conftest.sed < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_SED_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_SED="$ac_path_SED"
+      ac_path_SED_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_SED_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_SED"; then
+    as_fn_error $? "no acceptable sed could be found in \$PATH" "$LINENO" 5
+  fi
+else
+  ac_cv_path_SED=$SED
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_SED" >&5
+$as_echo "$ac_cv_path_SED" >&6; }
+ SED="$ac_cv_path_SED"
+  rm -f conftest.sed
+
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
 $as_echo_n "checking for ANSI C header files... " >&6; }
@@ -13564,6 +13638,699 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+  # Check for std::thread.  This does not work on some platforms, like
+  # mingw and DJGPP.
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+
+
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ax_pthread_ok=no
+
+# We used to check for pthread.h first, but this fails if pthread.h
+# requires special compiler flags (e.g. on Tru64 or Sequent).
+# It gets checked for in the link test anyway.
+
+# First of all, check if the user has set any of the PTHREAD_LIBS,
+# etcetera environment variables, and if threads linking works using
+# them:
+if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
+        ax_pthread_save_CC="$CC"
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        if test "x$PTHREAD_CC" != "x"; then :
+  CC="$PTHREAD_CC"
+fi
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS" >&5
+$as_echo_n "checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS... " >&6; }
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char pthread_join ();
+int
+main ()
+{
+return pthread_join ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xno"; then
+                PTHREAD_LIBS=""
+                PTHREAD_CFLAGS=""
+        fi
+        CC="$ax_pthread_save_CC"
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+fi
+
+# We must check for the threads library under a number of different
+# names; the ordering is very important because some systems
+# (e.g. DEC) have both -lpthread and -lpthreads, where one of the
+# libraries is broken (non-POSIX).
+
+# Create a list of thread flags to try.  Items starting with a "-" are
+# C compiler flags, and other items are library names, except for "none"
+# which indicates that we try without any flags at all, and "pthread-config"
+# which is a program returning the flags for the Pth emulation library.
+
+ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"
+
+# The ordering *is* (sometimes) important.  Some notes on the
+# individual items follow:
+
+# pthreads: AIX (must check this before -lpthread)
+# none: in case threads are in libc; should be tried before -Kthread and
+#       other compiler flags to prevent continual compiler warnings
+# -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)
+# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
+#           (Note: HP C rejects this with "bad form for `-t' option")
+# -pthreads: Solaris/gcc (Note: HP C also rejects)
+# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
+#      doesn't hurt to check since this sometimes defines pthreads and
+#      -D_REENTRANT too), HP C (must be checked before -lpthread, which
+#      is present but should not be used directly; and before -mthreads,
+#      because the compiler interprets this as "-mt" + "-hreads")
+# -mthreads: Mingw32/gcc, Lynx/gcc
+# pthread: Linux, etcetera
+# --thread-safe: KAI C++
+# pthread-config: use pthread-config program (for GNU Pth library)
+
+case $host_os in
+
+        freebsd*)
+
+        # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
+        # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
+
+        ax_pthread_flags="-kthread lthread $ax_pthread_flags"
+        ;;
+
+        hpux*)
+
+        # From the cc(1) man page: "[-mt] Sets various -D flags to enable
+        # multi-threading and also sets -lpthread."
+
+        ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
+        ;;
+
+        openedition*)
+
+        # IBM z/OS requires a feature-test macro to be defined in order to
+        # enable POSIX threads at all, so give the user a hint if this is
+        # not set. (We don't define these ourselves, as they can affect
+        # other portions of the system API in unpredictable ways.)
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
+             AX_PTHREAD_ZOS_MISSING
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_ZOS_MISSING" >/dev/null 2>&1; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&5
+$as_echo "$as_me: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&2;}
+fi
+rm -f conftest*
+
+        ;;
+
+        solaris*)
+
+        # On Solaris (at least, for some versions), libc contains stubbed
+        # (non-functional) versions of the pthreads routines, so link-based
+        # tests will erroneously succeed. (N.B.: The stubs are missing
+        # pthread_cleanup_push, or rather a function called by this macro,
+        # so we could check for that, but who knows whether they'll stub
+        # that too in a future libc.)  So we'll check first for the
+        # standard Solaris way of linking pthreads (-mt -lpthread).
+
+        ax_pthread_flags="-mt,pthread pthread $ax_pthread_flags"
+        ;;
+esac
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+if test "x$GCC" = "xyes"; then :
+  ax_pthread_flags="-pthread -pthreads $ax_pthread_flags"
+fi
+
+# The presence of a feature test macro requesting re-entrant function
+# definitions is, on some systems, a strong hint that pthreads support is
+# correctly enabled
+
+case $host_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
+
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+if test "x$ax_pthread_check_macro" = "x--"; then :
+  ax_pthread_check_cond=0
+else
+  ax_pthread_check_cond="!defined($ax_pthread_check_macro)"
+fi
+
+# Are we compiling with Clang?
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC is Clang" >&5
+$as_echo_n "checking whether $CC is Clang... " >&6; }
+if ${ax_cv_PTHREAD_CLANG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$GCC" = "xyes"; then
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+#            if defined(__clang__) && defined(__llvm__)
+             AX_PTHREAD_CC_IS_CLANG
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_CC_IS_CLANG" >/dev/null 2>&1; then :
+  ax_cv_PTHREAD_CLANG=yes
+fi
+rm -f conftest*
+
+     fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG" >&6; }
+ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+
+ax_pthread_clang_warning=no
+
+# Clang needs special handling, because older versions handle the -pthread
+# option in a rather... idiosyncratic way
+
+if test "x$ax_pthread_clang" = "xyes"; then
+
+        # Clang takes -pthread; it has never supported any other flag
+
+        # (Note 1: This will need to be revisited if a system that Clang
+        # supports has POSIX threads in a separate library.  This tends not
+        # to be the way of modern systems, but it's conceivable.)
+
+        # (Note 2: On some systems, notably Darwin, -pthread is not needed
+        # to get POSIX threads support; the API is always present and
+        # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
+        # -pthread does define _REENTRANT, and while the Darwin headers
+        # ignore this macro, third-party headers might not.)
+
+        PTHREAD_CFLAGS="-pthread"
+        PTHREAD_LIBS=
+
+        ax_pthread_ok=yes
+
+        # However, older versions of Clang make a point of warning the user
+        # that, in an invocation where only linking and no compilation is
+        # taking place, the -pthread option has no effect ("argument unused
+        # during compilation").  They expect -pthread to be passed in only
+        # when source code is being compiled.
+        #
+        # Problem is, this is at odds with the way Automake and most other
+        # C build frameworks function, which is that the same flags used in
+        # compilation (CFLAGS) are also used in linking.  Many systems
+        # supported by AX_PTHREAD require exactly this for POSIX threads
+        # support, and in fact it is often not straightforward to specify a
+        # flag that is used only in the compilation phase and not in
+        # linking.  Such a scenario is extremely rare in practice.
+        #
+        # Even though use of the -pthread flag in linking would only print
+        # a warning, this can be a nuisance for well-run software projects
+        # that build with -Werror.  So if the active version of Clang has
+        # this misfeature, we search for an option to squash it.
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread" >&5
+$as_echo_n "checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread... " >&6; }
+if ${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
+             # Create an alternate version of $ac_link that compiles and
+             # links in two steps (.c -> .o, .o -> exe) instead of one
+             # (.c -> exe), because the warning occurs only in the second
+             # step
+             ax_pthread_save_ac_link="$ac_link"
+             ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
+             ax_pthread_link_step=`$as_echo "$ac_link" | sed "$ax_pthread_sed"`
+             ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
+             ax_pthread_save_CFLAGS="$CFLAGS"
+             for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
+                if test "x$ax_pthread_try" = "xunknown"; then :
+  break
+fi
+                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                ac_link="$ax_pthread_save_ac_link"
+                cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_link="$ax_pthread_2step_ac_link"
+                     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+             ac_link="$ax_pthread_save_ac_link"
+             CFLAGS="$ax_pthread_save_CFLAGS"
+             if test "x$ax_pthread_try" = "x"; then :
+  ax_pthread_try=no
+fi
+             ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&6; }
+
+        case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
+                no | unknown) ;;
+                *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
+        esac
+
+fi # $ax_pthread_clang = yes
+
+if test "x$ax_pthread_ok" = "xno"; then
+for ax_pthread_try_flag in $ax_pthread_flags; do
+
+        case $ax_pthread_try_flag in
+                none)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work without any flags" >&5
+$as_echo_n "checking whether pthreads work without any flags... " >&6; }
+                ;;
+
+                -mt,pthread)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with -mt -lpthread" >&5
+$as_echo_n "checking whether pthreads work with -mt -lpthread... " >&6; }
+                PTHREAD_CFLAGS="-mt"
+                PTHREAD_LIBS="-lpthread"
+                ;;
+
+                -*)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with $ax_pthread_try_flag" >&5
+$as_echo_n "checking whether pthreads work with $ax_pthread_try_flag... " >&6; }
+                PTHREAD_CFLAGS="$ax_pthread_try_flag"
+                ;;
+
+                pthread-config)
+                # Extract the first word of "pthread-config", so it can be a program name with args.
+set dummy pthread-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_ax_pthread_config+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$ax_pthread_config"; then
+  ac_cv_prog_ax_pthread_config="$ax_pthread_config" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ax_pthread_config="yes"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  test -z "$ac_cv_prog_ax_pthread_config" && ac_cv_prog_ax_pthread_config="no"
+fi
+fi
+ax_pthread_config=$ac_cv_prog_ax_pthread_config
+if test -n "$ax_pthread_config"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_config" >&5
+$as_echo "$ax_pthread_config" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+                if test "x$ax_pthread_config" = "xno"; then :
+  continue
+fi
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking for the pthreads library -l$ax_pthread_try_flag" >&5
+$as_echo_n "checking for the pthreads library -l$ax_pthread_try_flag... " >&6; }
+                PTHREAD_LIBS="-l$ax_pthread_try_flag"
+                ;;
+        esac
+
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Check for various functions.  We must include pthread.h,
+        # since some functions may be macros.  (On the Sequent, we
+        # need a special flag -Kthread to make this header compile.)
+        # We check for pthread_join because it is in -lpthread on IRIX
+        # while pthread_create is in libc.  We check for pthread_attr_init
+        # due to DEC craziness with -lpthreads.  We check for
+        # pthread_cleanup_push because it is one of the few pthread
+        # functions on Solaris that doesn't have a non-functional libc stub.
+        # We try pthread_create on general principles.
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+#                       if $ax_pthread_check_cond
+#                        error "$ax_pthread_check_macro must be defined"
+#                       endif
+                        static void routine(void *a) { a = 0; }
+                        static void *start_routine(void *a) { return a; }
+int
+main ()
+{
+pthread_t th; pthread_attr_t attr;
+                        pthread_create(&th, 0, start_routine, 0);
+                        pthread_join(th, 0);
+                        pthread_attr_init(&attr);
+                        pthread_cleanup_push(routine, 0);
+                        pthread_cleanup_pop(0) /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xyes"; then :
+  break
+fi
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+# Various other checks:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for joinable pthread attribute" >&5
+$as_echo_n "checking for joinable pthread attribute... " >&6; }
+if ${ax_cv_PTHREAD_JOINABLE_ATTR+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int attr = $ax_pthread_attr; return attr /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_JOINABLE_ATTR" >&5
+$as_echo "$ax_cv_PTHREAD_JOINABLE_ATTR" >&6; }
+        if test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
+               test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
+               test "x$ax_pthread_joinable_attr_defined" != "xyes"; then :
+
+cat >>confdefs.h <<_ACEOF
+#define PTHREAD_CREATE_JOINABLE $ax_cv_PTHREAD_JOINABLE_ATTR
+_ACEOF
+
+               ax_pthread_joinable_attr_defined=yes
+
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether more special flags are required for pthreads" >&5
+$as_echo_n "checking whether more special flags are required for pthreads... " >&6; }
+if ${ax_cv_PTHREAD_SPECIAL_FLAGS+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_SPECIAL_FLAGS" >&5
+$as_echo "$ax_cv_PTHREAD_SPECIAL_FLAGS" >&6; }
+        if test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
+               test "x$ax_pthread_special_flags_added" != "xyes"; then :
+  PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for PTHREAD_PRIO_INHERIT" >&5
+$as_echo_n "checking for PTHREAD_PRIO_INHERIT... " >&6; }
+if ${ax_cv_PTHREAD_PRIO_INHERIT+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int i = PTHREAD_PRIO_INHERIT;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_PRIO_INHERIT=yes
+else
+  ax_cv_PTHREAD_PRIO_INHERIT=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_PRIO_INHERIT" >&5
+$as_echo "$ax_cv_PTHREAD_PRIO_INHERIT" >&6; }
+        if test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"; then :
+
+$as_echo "#define HAVE_PTHREAD_PRIO_INHERIT 1" >>confdefs.h
+
+               ax_pthread_prio_inherit_defined=yes
+
+fi
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        # More AIX lossage: compile with *_r variant
+        if test "x$GCC" != "xyes"; then
+            case $host_os in
+                aix*)
+                case "x/$CC" in #(
+  x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6) :
+    #handle absolute path differently from PATH based program lookup
+                     case "x$CC" in #(
+  x/*) :
+    if as_fn_executable_p ${CC}_r; then :
+  PTHREAD_CC="${CC}_r"
+fi ;; #(
+  *) :
+    for ac_prog in ${CC}_r
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_PTHREAD_CC+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$PTHREAD_CC"; then
+  ac_cv_prog_PTHREAD_CC="$PTHREAD_CC" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_PTHREAD_CC="$ac_prog"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+PTHREAD_CC=$ac_cv_prog_PTHREAD_CC
+if test -n "$PTHREAD_CC"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PTHREAD_CC" >&5
+$as_echo "$PTHREAD_CC" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+  test -n "$PTHREAD_CC" && break
+done
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+ ;;
+esac ;; #(
+  *) :
+     ;;
+esac
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+
+
+
+
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+        threads=yes
+        :
+else
+        ax_pthread_ok=no
+        threads=no
+fi
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+  if test "$threads" = "yes"; then
+    save_LIBS="$LIBS"
+    LIBS="$PTHREAD_LIBS $LIBS"
+    save_CXXFLAGS="$CXXFLAGS"
+    CXXFLAGS="$PTHREAD_CFLAGS $save_CFLAGS"
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for std::thread" >&5
+$as_echo_n "checking for std::thread... " >&6; }
+if ${gdb_cv_cxx_std_thread+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <thread>
+      void callback() { }
+int
+main ()
+{
+std::thread t(callback);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  gdb_cv_cxx_std_thread=yes
+else
+  gdb_cv_cxx_std_thread=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gdb_cv_cxx_std_thread" >&5
+$as_echo "$gdb_cv_cxx_std_thread" >&6; }
+    LIBS="$save_LIBS"
+    CXXFLAGS="$save_CXXFLAGS"
+  fi
+  if test $gdb_cv_cxx_std_thread = yes; then
+
+$as_echo "#define CXX_STD_THREAD 1" >>confdefs.h
+
+  fi
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sigsetjmp" >&5
 $as_echo_n "checking for sigsetjmp... " >&6; }
 if ${gdb_cv_func_sigsetjmp+:} false; then :
diff --git a/gdb/gdbserver/acinclude.m4 b/gdb/gdbserver/acinclude.m4
index 880c03ac1db..4c18e9b01db 100644
--- a/gdb/gdbserver/acinclude.m4
+++ b/gdb/gdbserver/acinclude.m4
@@ -31,6 +31,8 @@ m4_include(../ax_cxx_compile_stdcxx.m4)
 dnl For GDB_AC_SELFTEST.
 m4_include(../selftest.m4)
 
+m4_include([../../config/ax_pthread.m4])
+
 dnl Check for existence of a type $1 in libthread_db.h
 dnl Based on BFD_HAVE_SYS_PROCFS_TYPE in bfd/bfd.m4.
 
diff --git a/gdb/gdbserver/config.in b/gdb/gdbserver/config.in
index f05e9be48ad..fb612723613 100644
--- a/gdb/gdbserver/config.in
+++ b/gdb/gdbserver/config.in
@@ -5,6 +5,9 @@
    */
 #undef CRAY_STACKSEG_END
 
+/* Define to 1 if std::thread works. */
+#undef CXX_STD_THREAD
+
 /* Define to 1 if using `alloca.c'. */
 #undef C_ALLOCA
 
diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
index 692cb0f3082..aa13ce6aa4b 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -636,6 +636,11 @@ WERROR_CFLAGS
 WARN_CFLAGS
 ustinc
 ustlibs
+PTHREAD_CFLAGS
+PTHREAD_LIBS
+PTHREAD_CC
+ax_pthread_config
+SED
 ALLOCA
 CCDEPMODE
 CONFIG_SRC_SUBDIR
@@ -6472,6 +6477,75 @@ _ACEOF
 
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for a sed that does not truncate output" >&5
+$as_echo_n "checking for a sed that does not truncate output... " >&6; }
+if ${ac_cv_path_SED+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+            ac_script=s/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/
+     for ac_i in 1 2 3 4 5 6 7; do
+       ac_script="$ac_script$as_nl$ac_script"
+     done
+     echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
+     { ac_script=; unset ac_script;}
+     if test -z "$SED"; then
+  ac_path_SED_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in sed gsed; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_SED="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_SED" || continue
+# Check for GNU ac_path_SED and select it if it is found.
+  # Check for GNU $ac_path_SED
+case `"$ac_path_SED" --version 2>&1` in
+*GNU*)
+  ac_cv_path_SED="$ac_path_SED" ac_path_SED_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo '' >> "conftest.nl"
+    "$ac_path_SED" -f conftest.sed < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_SED_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_SED="$ac_path_SED"
+      ac_path_SED_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_SED_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_SED"; then
+    as_fn_error $? "no acceptable sed could be found in \$PATH" "$LINENO" 5
+  fi
+else
+  ac_cv_path_SED=$SED
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_SED" >&5
+$as_echo "$ac_cv_path_SED" >&6; }
+ SED="$ac_cv_path_SED"
+  rm -f conftest.sed
+
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
 $as_echo_n "checking for ANSI C header files... " >&6; }
@@ -6856,6 +6930,699 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+  # Check for std::thread.  This does not work on some platforms, like
+  # mingw and DJGPP.
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+
+
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ax_pthread_ok=no
+
+# We used to check for pthread.h first, but this fails if pthread.h
+# requires special compiler flags (e.g. on Tru64 or Sequent).
+# It gets checked for in the link test anyway.
+
+# First of all, check if the user has set any of the PTHREAD_LIBS,
+# etcetera environment variables, and if threads linking works using
+# them:
+if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
+        ax_pthread_save_CC="$CC"
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        if test "x$PTHREAD_CC" != "x"; then :
+  CC="$PTHREAD_CC"
+fi
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS" >&5
+$as_echo_n "checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS... " >&6; }
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char pthread_join ();
+int
+main ()
+{
+return pthread_join ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xno"; then
+                PTHREAD_LIBS=""
+                PTHREAD_CFLAGS=""
+        fi
+        CC="$ax_pthread_save_CC"
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+fi
+
+# We must check for the threads library under a number of different
+# names; the ordering is very important because some systems
+# (e.g. DEC) have both -lpthread and -lpthreads, where one of the
+# libraries is broken (non-POSIX).
+
+# Create a list of thread flags to try.  Items starting with a "-" are
+# C compiler flags, and other items are library names, except for "none"
+# which indicates that we try without any flags at all, and "pthread-config"
+# which is a program returning the flags for the Pth emulation library.
+
+ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"
+
+# The ordering *is* (sometimes) important.  Some notes on the
+# individual items follow:
+
+# pthreads: AIX (must check this before -lpthread)
+# none: in case threads are in libc; should be tried before -Kthread and
+#       other compiler flags to prevent continual compiler warnings
+# -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)
+# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
+#           (Note: HP C rejects this with "bad form for `-t' option")
+# -pthreads: Solaris/gcc (Note: HP C also rejects)
+# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
+#      doesn't hurt to check since this sometimes defines pthreads and
+#      -D_REENTRANT too), HP C (must be checked before -lpthread, which
+#      is present but should not be used directly; and before -mthreads,
+#      because the compiler interprets this as "-mt" + "-hreads")
+# -mthreads: Mingw32/gcc, Lynx/gcc
+# pthread: Linux, etcetera
+# --thread-safe: KAI C++
+# pthread-config: use pthread-config program (for GNU Pth library)
+
+case $host_os in
+
+        freebsd*)
+
+        # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
+        # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
+
+        ax_pthread_flags="-kthread lthread $ax_pthread_flags"
+        ;;
+
+        hpux*)
+
+        # From the cc(1) man page: "[-mt] Sets various -D flags to enable
+        # multi-threading and also sets -lpthread."
+
+        ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
+        ;;
+
+        openedition*)
+
+        # IBM z/OS requires a feature-test macro to be defined in order to
+        # enable POSIX threads at all, so give the user a hint if this is
+        # not set. (We don't define these ourselves, as they can affect
+        # other portions of the system API in unpredictable ways.)
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
+             AX_PTHREAD_ZOS_MISSING
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_ZOS_MISSING" >/dev/null 2>&1; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&5
+$as_echo "$as_me: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&2;}
+fi
+rm -f conftest*
+
+        ;;
+
+        solaris*)
+
+        # On Solaris (at least, for some versions), libc contains stubbed
+        # (non-functional) versions of the pthreads routines, so link-based
+        # tests will erroneously succeed. (N.B.: The stubs are missing
+        # pthread_cleanup_push, or rather a function called by this macro,
+        # so we could check for that, but who knows whether they'll stub
+        # that too in a future libc.)  So we'll check first for the
+        # standard Solaris way of linking pthreads (-mt -lpthread).
+
+        ax_pthread_flags="-mt,pthread pthread $ax_pthread_flags"
+        ;;
+esac
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+if test "x$GCC" = "xyes"; then :
+  ax_pthread_flags="-pthread -pthreads $ax_pthread_flags"
+fi
+
+# The presence of a feature test macro requesting re-entrant function
+# definitions is, on some systems, a strong hint that pthreads support is
+# correctly enabled
+
+case $host_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
+
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+if test "x$ax_pthread_check_macro" = "x--"; then :
+  ax_pthread_check_cond=0
+else
+  ax_pthread_check_cond="!defined($ax_pthread_check_macro)"
+fi
+
+# Are we compiling with Clang?
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC is Clang" >&5
+$as_echo_n "checking whether $CC is Clang... " >&6; }
+if ${ax_cv_PTHREAD_CLANG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$GCC" = "xyes"; then
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+#            if defined(__clang__) && defined(__llvm__)
+             AX_PTHREAD_CC_IS_CLANG
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_CC_IS_CLANG" >/dev/null 2>&1; then :
+  ax_cv_PTHREAD_CLANG=yes
+fi
+rm -f conftest*
+
+     fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG" >&6; }
+ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+
+ax_pthread_clang_warning=no
+
+# Clang needs special handling, because older versions handle the -pthread
+# option in a rather... idiosyncratic way
+
+if test "x$ax_pthread_clang" = "xyes"; then
+
+        # Clang takes -pthread; it has never supported any other flag
+
+        # (Note 1: This will need to be revisited if a system that Clang
+        # supports has POSIX threads in a separate library.  This tends not
+        # to be the way of modern systems, but it's conceivable.)
+
+        # (Note 2: On some systems, notably Darwin, -pthread is not needed
+        # to get POSIX threads support; the API is always present and
+        # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
+        # -pthread does define _REENTRANT, and while the Darwin headers
+        # ignore this macro, third-party headers might not.)
+
+        PTHREAD_CFLAGS="-pthread"
+        PTHREAD_LIBS=
+
+        ax_pthread_ok=yes
+
+        # However, older versions of Clang make a point of warning the user
+        # that, in an invocation where only linking and no compilation is
+        # taking place, the -pthread option has no effect ("argument unused
+        # during compilation").  They expect -pthread to be passed in only
+        # when source code is being compiled.
+        #
+        # Problem is, this is at odds with the way Automake and most other
+        # C build frameworks function, which is that the same flags used in
+        # compilation (CFLAGS) are also used in linking.  Many systems
+        # supported by AX_PTHREAD require exactly this for POSIX threads
+        # support, and in fact it is often not straightforward to specify a
+        # flag that is used only in the compilation phase and not in
+        # linking.  Such a scenario is extremely rare in practice.
+        #
+        # Even though use of the -pthread flag in linking would only print
+        # a warning, this can be a nuisance for well-run software projects
+        # that build with -Werror.  So if the active version of Clang has
+        # this misfeature, we search for an option to squash it.
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread" >&5
+$as_echo_n "checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread... " >&6; }
+if ${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
+             # Create an alternate version of $ac_link that compiles and
+             # links in two steps (.c -> .o, .o -> exe) instead of one
+             # (.c -> exe), because the warning occurs only in the second
+             # step
+             ax_pthread_save_ac_link="$ac_link"
+             ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
+             ax_pthread_link_step=`$as_echo "$ac_link" | sed "$ax_pthread_sed"`
+             ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
+             ax_pthread_save_CFLAGS="$CFLAGS"
+             for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
+                if test "x$ax_pthread_try" = "xunknown"; then :
+  break
+fi
+                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                ac_link="$ax_pthread_save_ac_link"
+                cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_link="$ax_pthread_2step_ac_link"
+                     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+             ac_link="$ax_pthread_save_ac_link"
+             CFLAGS="$ax_pthread_save_CFLAGS"
+             if test "x$ax_pthread_try" = "x"; then :
+  ax_pthread_try=no
+fi
+             ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&6; }
+
+        case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
+                no | unknown) ;;
+                *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
+        esac
+
+fi # $ax_pthread_clang = yes
+
+if test "x$ax_pthread_ok" = "xno"; then
+for ax_pthread_try_flag in $ax_pthread_flags; do
+
+        case $ax_pthread_try_flag in
+                none)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work without any flags" >&5
+$as_echo_n "checking whether pthreads work without any flags... " >&6; }
+                ;;
+
+                -mt,pthread)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with -mt -lpthread" >&5
+$as_echo_n "checking whether pthreads work with -mt -lpthread... " >&6; }
+                PTHREAD_CFLAGS="-mt"
+                PTHREAD_LIBS="-lpthread"
+                ;;
+
+                -*)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with $ax_pthread_try_flag" >&5
+$as_echo_n "checking whether pthreads work with $ax_pthread_try_flag... " >&6; }
+                PTHREAD_CFLAGS="$ax_pthread_try_flag"
+                ;;
+
+                pthread-config)
+                # Extract the first word of "pthread-config", so it can be a program name with args.
+set dummy pthread-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_ax_pthread_config+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$ax_pthread_config"; then
+  ac_cv_prog_ax_pthread_config="$ax_pthread_config" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ax_pthread_config="yes"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  test -z "$ac_cv_prog_ax_pthread_config" && ac_cv_prog_ax_pthread_config="no"
+fi
+fi
+ax_pthread_config=$ac_cv_prog_ax_pthread_config
+if test -n "$ax_pthread_config"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_config" >&5
+$as_echo "$ax_pthread_config" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+                if test "x$ax_pthread_config" = "xno"; then :
+  continue
+fi
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking for the pthreads library -l$ax_pthread_try_flag" >&5
+$as_echo_n "checking for the pthreads library -l$ax_pthread_try_flag... " >&6; }
+                PTHREAD_LIBS="-l$ax_pthread_try_flag"
+                ;;
+        esac
+
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Check for various functions.  We must include pthread.h,
+        # since some functions may be macros.  (On the Sequent, we
+        # need a special flag -Kthread to make this header compile.)
+        # We check for pthread_join because it is in -lpthread on IRIX
+        # while pthread_create is in libc.  We check for pthread_attr_init
+        # due to DEC craziness with -lpthreads.  We check for
+        # pthread_cleanup_push because it is one of the few pthread
+        # functions on Solaris that doesn't have a non-functional libc stub.
+        # We try pthread_create on general principles.
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+#                       if $ax_pthread_check_cond
+#                        error "$ax_pthread_check_macro must be defined"
+#                       endif
+                        static void routine(void *a) { a = 0; }
+                        static void *start_routine(void *a) { return a; }
+int
+main ()
+{
+pthread_t th; pthread_attr_t attr;
+                        pthread_create(&th, 0, start_routine, 0);
+                        pthread_join(th, 0);
+                        pthread_attr_init(&attr);
+                        pthread_cleanup_push(routine, 0);
+                        pthread_cleanup_pop(0) /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xyes"; then :
+  break
+fi
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+# Various other checks:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for joinable pthread attribute" >&5
+$as_echo_n "checking for joinable pthread attribute... " >&6; }
+if ${ax_cv_PTHREAD_JOINABLE_ATTR+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int attr = $ax_pthread_attr; return attr /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_JOINABLE_ATTR" >&5
+$as_echo "$ax_cv_PTHREAD_JOINABLE_ATTR" >&6; }
+        if test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
+               test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
+               test "x$ax_pthread_joinable_attr_defined" != "xyes"; then :
+
+cat >>confdefs.h <<_ACEOF
+#define PTHREAD_CREATE_JOINABLE $ax_cv_PTHREAD_JOINABLE_ATTR
+_ACEOF
+
+               ax_pthread_joinable_attr_defined=yes
+
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether more special flags are required for pthreads" >&5
+$as_echo_n "checking whether more special flags are required for pthreads... " >&6; }
+if ${ax_cv_PTHREAD_SPECIAL_FLAGS+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_SPECIAL_FLAGS" >&5
+$as_echo "$ax_cv_PTHREAD_SPECIAL_FLAGS" >&6; }
+        if test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
+               test "x$ax_pthread_special_flags_added" != "xyes"; then :
+  PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for PTHREAD_PRIO_INHERIT" >&5
+$as_echo_n "checking for PTHREAD_PRIO_INHERIT... " >&6; }
+if ${ax_cv_PTHREAD_PRIO_INHERIT+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int i = PTHREAD_PRIO_INHERIT;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_PRIO_INHERIT=yes
+else
+  ax_cv_PTHREAD_PRIO_INHERIT=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_PRIO_INHERIT" >&5
+$as_echo "$ax_cv_PTHREAD_PRIO_INHERIT" >&6; }
+        if test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"; then :
+
+$as_echo "#define HAVE_PTHREAD_PRIO_INHERIT 1" >>confdefs.h
+
+               ax_pthread_prio_inherit_defined=yes
+
+fi
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        # More AIX lossage: compile with *_r variant
+        if test "x$GCC" != "xyes"; then
+            case $host_os in
+                aix*)
+                case "x/$CC" in #(
+  x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6) :
+    #handle absolute path differently from PATH based program lookup
+                     case "x$CC" in #(
+  x/*) :
+    if as_fn_executable_p ${CC}_r; then :
+  PTHREAD_CC="${CC}_r"
+fi ;; #(
+  *) :
+    for ac_prog in ${CC}_r
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_PTHREAD_CC+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$PTHREAD_CC"; then
+  ac_cv_prog_PTHREAD_CC="$PTHREAD_CC" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_PTHREAD_CC="$ac_prog"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+PTHREAD_CC=$ac_cv_prog_PTHREAD_CC
+if test -n "$PTHREAD_CC"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PTHREAD_CC" >&5
+$as_echo "$PTHREAD_CC" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+  test -n "$PTHREAD_CC" && break
+done
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+ ;;
+esac ;; #(
+  *) :
+     ;;
+esac
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+
+
+
+
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+        threads=yes
+        :
+else
+        ax_pthread_ok=no
+        threads=no
+fi
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+  if test "$threads" = "yes"; then
+    save_LIBS="$LIBS"
+    LIBS="$PTHREAD_LIBS $LIBS"
+    save_CXXFLAGS="$CXXFLAGS"
+    CXXFLAGS="$PTHREAD_CFLAGS $save_CFLAGS"
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for std::thread" >&5
+$as_echo_n "checking for std::thread... " >&6; }
+if ${gdb_cv_cxx_std_thread+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <thread>
+      void callback() { }
+int
+main ()
+{
+std::thread t(callback);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  gdb_cv_cxx_std_thread=yes
+else
+  gdb_cv_cxx_std_thread=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gdb_cv_cxx_std_thread" >&5
+$as_echo "$gdb_cv_cxx_std_thread" >&6; }
+    LIBS="$save_LIBS"
+    CXXFLAGS="$save_CXXFLAGS"
+  fi
+  if test $gdb_cv_cxx_std_thread = yes; then
+
+$as_echo "#define CXX_STD_THREAD 1" >>confdefs.h
+
+  fi
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sigsetjmp" >&5
 $as_echo_n "checking for sigsetjmp... " >&6; }
 if ${gdb_cv_func_sigsetjmp+:} false; then :
diff --git a/gdb/gdbsupport/common.m4 b/gdb/gdbsupport/common.m4
index 903889463f1..0f0e9a866eb 100644
--- a/gdb/gdbsupport/common.m4
+++ b/gdb/gdbsupport/common.m4
@@ -36,6 +36,32 @@ AC_DEFUN([GDB_AC_COMMON], [
 
   AC_CHECK_DECLS([strerror, strstr])
 
+  # Check for std::thread.  This does not work on some platforms, like
+  # mingw and DJGPP.
+  AC_LANG_PUSH([C++])
+  AX_PTHREAD([threads=yes], [threads=no])
+  if test "$threads" = "yes"; then
+    save_LIBS="$LIBS"
+    LIBS="$PTHREAD_LIBS $LIBS"
+    save_CXXFLAGS="$CXXFLAGS"
+    CXXFLAGS="$PTHREAD_CFLAGS $save_CFLAGS"
+    AC_CACHE_CHECK([for std::thread],
+		   gdb_cv_cxx_std_thread,
+		   [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+    [[#include <thread>
+      void callback() { }]],
+    [[std::thread t(callback);]])],
+				  gdb_cv_cxx_std_thread=yes,
+				  gdb_cv_cxx_std_thread=no)])
+    LIBS="$save_LIBS"
+    CXXFLAGS="$save_CXXFLAGS"
+  fi
+  if test $gdb_cv_cxx_std_thread = yes; then
+    AC_DEFINE(CXX_STD_THREAD, 1,
+	      [Define to 1 if std::thread works.])
+  fi
+  AC_LANG_POP
+
   dnl Check if sigsetjmp is available.  Using AC_CHECK_FUNCS won't
   dnl do since sigsetjmp might only be defined as a macro.
 AC_CACHE_CHECK([for sigsetjmp], gdb_cv_func_sigsetjmp,
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 01/11] Use m4_include, not sinclude in .m4 files
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (3 preceding siblings ...)
  2019-10-01 20:12 ` [PATCH v4 08/11] Introduce thread-safe way to handle SIGSEGV Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 11/11] Use run_on_main_thread in gdb.post_event Tom Tromey
                   ` (6 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

Pedro pointed out that sinclude does not error if a file is missing.
This patch changes gdb to only use m4_include, which seems more
correct.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.
	* acinclude.m4: Use m4_include, not sinclude.

gdb/gdbserver/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.
	* acinclude.m4: Use m4_include, not sinclude.

gdb/testsuite/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.
	* aclocal.m4: Use m4_include, not sinclude.
---
 gdb/ChangeLog              |  5 +++++
 gdb/acinclude.m4           | 44 +++++++++++++++++++-------------------
 gdb/gdbserver/ChangeLog    |  5 +++++
 gdb/gdbserver/acinclude.m4 | 10 ++++-----
 gdb/testsuite/ChangeLog    |  5 +++++
 gdb/testsuite/aclocal.m4   |  6 +++---
 6 files changed, 45 insertions(+), 30 deletions(-)

diff --git a/gdb/acinclude.m4 b/gdb/acinclude.m4
index 6e81aaed3bf..5f1358b8207 100644
--- a/gdb/acinclude.m4
+++ b/gdb/acinclude.m4
@@ -4,64 +4,64 @@ dnl major rewriting for Tcl 7.5 by Don Libes <libes@nist.gov>
 # Keep these includes in sync with the aclocal_m4_deps list in
 # Makefile.in.
 
-sinclude(acx_configure_dir.m4)
+m4_include(acx_configure_dir.m4)
 
 # This gets GDB_AC_TRANSFORM.
-sinclude(transform.m4)
+m4_include(transform.m4)
 
 # This gets AM_GDB_WARNINGS.
-sinclude(warning.m4)
+m4_include(warning.m4)
 
 # AM_GDB_UBSAN
-sinclude(sanitize.m4)
+m4_include(sanitize.m4)
 
 # This gets GDB_AC_SELFTEST.
-sinclude(selftest.m4)
+m4_include(selftest.m4)
 
 dnl gdb/configure.in uses BFD_NEED_DECLARATION, so get its definition.
-sinclude(../bfd/bfd.m4)
+m4_include(../bfd/bfd.m4)
 
 dnl This gets the standard macros.
-sinclude(../config/acinclude.m4)
+m4_include(../config/acinclude.m4)
 
 dnl This gets AC_PLUGINS, needed by ACX_LARGEFILE.
-sinclude(../config/plugins.m4)
+m4_include(../config/plugins.m4)
 
 dnl For ACX_LARGEFILE.
-sinclude(../config/largefile.m4)
+m4_include(../config/largefile.m4)
 
 dnl For AM_SET_LEADING_DOT.
-sinclude(../config/lead-dot.m4)
+m4_include(../config/lead-dot.m4)
 
 dnl This gets autoconf bugfixes.
-sinclude(../config/override.m4)
+m4_include(../config/override.m4)
 
 dnl For ZW_GNU_GETTEXT_SISTER_DIR.
-sinclude(../config/gettext-sister.m4)
+m4_include(../config/gettext-sister.m4)
 
 dnl For AC_LIB_HAVE_LINKFLAGS.
-sinclude(../config/lib-ld.m4)
-sinclude(../config/lib-prefix.m4)
-sinclude(../config/lib-link.m4)
+m4_include(../config/lib-ld.m4)
+m4_include(../config/lib-prefix.m4)
+m4_include(../config/lib-link.m4)
 
 dnl For ACX_PKGVERSION and ACX_BUGURL.
-sinclude(../config/acx.m4)
+m4_include(../config/acx.m4)
 
 dnl for TCL definitions
-sinclude(../config/tcl.m4)
+m4_include(../config/tcl.m4)
 
 dnl For dependency tracking macros.
-sinclude([../config/depstand.m4])
+m4_include([../config/depstand.m4])
 
 dnl For AM_LC_MESSAGES
-sinclude([../config/lcmessage.m4])
+m4_include([../config/lcmessage.m4])
 
 dnl For AM_LANGINFO_CODESET.
-sinclude([../config/codeset.m4])
+m4_include([../config/codeset.m4])
 
-sinclude([../config/iconv.m4])
+m4_include([../config/iconv.m4])
 
-sinclude([../config/zlib.m4])
+m4_include([../config/zlib.m4])
 
 m4_include([gdbsupport/common.m4])
 
diff --git a/gdb/gdbserver/acinclude.m4 b/gdb/gdbserver/acinclude.m4
index 3887b165c66..880c03ac1db 100644
--- a/gdb/gdbserver/acinclude.m4
+++ b/gdb/gdbserver/acinclude.m4
@@ -1,16 +1,16 @@
 dnl gdb/gdbserver/configure.in uses BFD_HAVE_SYS_PROCFS_TYPE.
-sinclude(../../bfd/bfd.m4)
+m4_include(../../bfd/bfd.m4)
 
-sinclude(../acx_configure_dir.m4)
+m4_include(../acx_configure_dir.m4)
 
 # This gets AM_GDB_WARNINGS.
-sinclude(../warning.m4)
+m4_include(../warning.m4)
 
 dnl This gets autoconf bugfixes
-sinclude(../../config/override.m4)
+m4_include(../../config/override.m4)
 
 dnl For ACX_PKGVERSION and ACX_BUGURL.
-sinclude(../../config/acx.m4)
+m4_include(../../config/acx.m4)
 
 m4_include(../../config/depstand.m4)
 m4_include(../../config/lead-dot.m4)
diff --git a/gdb/testsuite/aclocal.m4 b/gdb/testsuite/aclocal.m4
index d40c3a9fc6a..5061eef5372 100644
--- a/gdb/testsuite/aclocal.m4
+++ b/gdb/testsuite/aclocal.m4
@@ -1,6 +1,6 @@
-sinclude(../../config/acx.m4)
-sinclude(../../config/override.m4)
-sinclude(../transform.m4)
+m4_include(../../config/acx.m4)
+m4_include(../../config/override.m4)
+m4_include(../transform.m4)
 
 # AM_CONDITIONAL                                            -*- Autoconf -*-
 
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 08/11] Introduce thread-safe way to handle SIGSEGV
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (2 preceding siblings ...)
  2019-10-01 20:12 ` [PATCH v4 09/11] Demangle minsyms in parallel Tom Tromey
@ 2019-10-01 20:12 ` Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 01/11] Use m4_include, not sinclude in .m4 files Tom Tromey
                   ` (7 subsequent siblings)
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:12 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

The gdb demangler installs a SIGSEGV handler in order to protect gdb
from demangler bugs.  However, this is not thread-safe, as signal
handlers are global to the process.

This patch changes gdb to always install a global SIGSEGV handler, and
then lets threads indicate their interest in handling the signal by
setting a thread-local variable.

This patch then arranges for the demangler code to use this; being
sure to arrange for calls to warning and the like to be done on the
main thread.

One thing I wondered while writing this patch is if there are any
systems that do not have "sigaction".  If gdb could assume this, it
would simplify this code.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* event-top.h (thread_local_segv_handler): Declare.
	* event-top.c (thread_local_segv_handler): New global.
	(install_handle_sigsegv, handle_sigsegv): New functions.
	(async_init_signals): Install SIGSEGV handler.
	* cp-support.c (gdb_demangle_jmp_buf): Change type.  Now
	thread-local.
	(report_failed_demangle): New function.
	(gdb_demangle): Make core_dump_allowed atomic.  Remove signal
	handler-setting code, instead use segv_handler.  Run warning code
	on main thread.
---
 gdb/ChangeLog    |  13 +++++
 gdb/cp-support.c | 143 +++++++++++++++++++++++------------------------
 gdb/event-top.c  |  41 ++++++++++++++
 gdb/event-top.h  |   6 ++
 4 files changed, 130 insertions(+), 73 deletions(-)

diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index cd732b60e7d..8fe9ea161f9 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -37,6 +37,9 @@
 #include "gdbsupport/gdb_setjmp.h"
 #include "safe-ctype.h"
 #include "gdbsupport/selftest.h"
+#include <atomic>
+#include "event-top.h"
+#include "ser-event.h"
 
 #define d_left(dc) (dc)->u.s_binary.left
 #define d_right(dc) (dc)->u.s_binary.right
@@ -1476,11 +1479,11 @@ static bool catch_demangler_crashes = true;
 
 /* Stack context and environment for demangler crash recovery.  */
 
-static SIGJMP_BUF gdb_demangle_jmp_buf;
+static thread_local SIGJMP_BUF *gdb_demangle_jmp_buf;
 
 /* If nonzero, attempt to dump core from the signal handler.  */
 
-static int gdb_demangle_attempt_core_dump = 1;
+static std::atomic<bool> gdb_demangle_attempt_core_dump;
 
 /* Signal handler for gdb_demangle.  */
 
@@ -1492,10 +1495,46 @@ gdb_demangle_signal_handler (int signo)
       if (fork () == 0)
 	dump_core ();
 
-      gdb_demangle_attempt_core_dump = 0;
+      gdb_demangle_attempt_core_dump = false;
     }
 
-  SIGLONGJMP (gdb_demangle_jmp_buf, signo);
+  SIGLONGJMP (*gdb_demangle_jmp_buf, signo);
+}
+
+/* A helper for gdb_demangle that reports a demangling failure.  */
+
+static void
+report_failed_demangle (const char *name, bool core_dump_allowed,
+			int crash_signal)
+{
+  static bool error_reported = false;
+
+  if (!error_reported)
+    {
+      std::string short_msg
+	= string_printf (_("unable to demangle '%s' "
+			   "(demangler failed with signal %d)"),
+			 name, crash_signal);
+
+      std::string long_msg
+	= string_printf ("%s:%d: %s: %s", __FILE__, __LINE__,
+			 "demangler-warning", short_msg.c_str ());
+
+      target_terminal::scoped_restore_terminal_state term_state;
+      target_terminal::ours_for_output ();
+
+      begin_line ();
+      if (core_dump_allowed)
+	fprintf_unfiltered (gdb_stderr,
+			    _("%s\nAttempting to dump core.\n"),
+			    long_msg.c_str ());
+      else
+	warn_cant_dump_core (long_msg.c_str ());
+
+      demangler_warning (__FILE__, __LINE__, "%s", short_msg.c_str ());
+
+      error_reported = true;
+    }
 }
 
 #endif
@@ -1509,38 +1548,18 @@ gdb_demangle (const char *name, int options)
   int crash_signal = 0;
 
 #ifdef HAVE_WORKING_FORK
-#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
-  struct sigaction sa, old_sa;
-#else
-  sighandler_t ofunc;
-#endif
-  static int core_dump_allowed = -1;
-
-  if (core_dump_allowed == -1)
-    {
-      core_dump_allowed = can_dump_core (LIMIT_CUR);
-
-      if (!core_dump_allowed)
-	gdb_demangle_attempt_core_dump = 0;
-    }
-
+  scoped_restore restore_segv
+    = make_scoped_restore (&thread_local_segv_handler,
+			   catch_demangler_crashes
+			   ? gdb_demangle_signal_handler
+			   : nullptr);
+
+  bool core_dump_allowed = gdb_demangle_attempt_core_dump;
+  SIGJMP_BUF jmp_buf;
+  scoped_restore restore_jmp_buf
+    = make_scoped_restore (&gdb_demangle_jmp_buf, &jmp_buf);
   if (catch_demangler_crashes)
-    {
-#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
-      sa.sa_handler = gdb_demangle_signal_handler;
-      sigemptyset (&sa.sa_mask);
-#ifdef HAVE_SIGALTSTACK
-      sa.sa_flags = SA_ONSTACK;
-#else
-      sa.sa_flags = 0;
-#endif
-      sigaction (SIGSEGV, &sa, &old_sa);
-#else
-      ofunc = signal (SIGSEGV, gdb_demangle_signal_handler);
-#endif
-
-      crash_signal = SIGSETJMP (gdb_demangle_jmp_buf);
-    }
+    crash_signal = SIGSETJMP (jmp_buf);
 #endif
 
   if (crash_signal == 0)
@@ -1549,45 +1568,20 @@ gdb_demangle (const char *name, int options)
 #ifdef HAVE_WORKING_FORK
   if (catch_demangler_crashes)
     {
-#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
-      sigaction (SIGSEGV, &old_sa, NULL);
-#else
-      signal (SIGSEGV, ofunc);
-#endif
-
       if (crash_signal != 0)
-	{
-	  static int error_reported = 0;
-
-	  if (!error_reported)
-	    {
-	      std::string short_msg
-		= string_printf (_("unable to demangle '%s' "
-				   "(demangler failed with signal %d)"),
-				 name, crash_signal);
-
-	      std::string long_msg
-		= string_printf ("%s:%d: %s: %s", __FILE__, __LINE__,
-				 "demangler-warning", short_msg.c_str ());
-
-	      target_terminal::scoped_restore_terminal_state term_state;
-	      target_terminal::ours_for_output ();
-
-	      begin_line ();
-	      if (core_dump_allowed)
-		fprintf_unfiltered (gdb_stderr,
-				    _("%s\nAttempting to dump core.\n"),
-				    long_msg.c_str ());
-	      else
-		warn_cant_dump_core (long_msg.c_str ());
-
-	      demangler_warning (__FILE__, __LINE__, "%s", short_msg.c_str ());
-
-	      error_reported = 1;
-	    }
-
-	  result = NULL;
-	}
+        {
+	  /* If there was a failure, we can't report it here, because
+	     we might be in a background thread.  Instead, arrange for
+	     the reporting to happen on the main thread.  */
+          std::string copy = name;
+          run_on_main_thread ([=] ()
+            {
+              report_failed_demangle (copy.c_str (), core_dump_allowed,
+                                      crash_signal);
+            });
+
+          result = NULL;
+        }
     }
 #endif
 
@@ -2194,4 +2188,7 @@ display the offending symbol."),
   selftests::register_test ("cp_remove_params",
 			    selftests::test_cp_remove_params);
 #endif
+
+  if (!can_dump_core (LIMIT_CUR))
+    gdb_demangle_attempt_core_dump = false;
 }
diff --git a/gdb/event-top.c b/gdb/event-top.c
index 0b05b2f85a5..ad9e3ff4d9c 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -847,6 +847,45 @@ gdb_readline_no_editing_callback (gdb_client_data client_data)
 }
 \f
 
+/* See event-top.h.  */
+
+thread_local void (*thread_local_segv_handler) (int);
+
+static void handle_sigsegv (int sig);
+
+/* Install the SIGSEGV handler.  */
+static void
+install_handle_sigsegv ()
+{
+#if defined (HAVE_SIGACTION)
+  struct sigaction sa;
+  sa.sa_handler = handle_sigsegv;
+  sigemptyset (&sa.sa_mask);
+#ifdef HAVE_SIGALTSTACK
+  sa.sa_flags = SA_ONSTACK;
+#else
+  sa.sa_flags = 0;
+#endif
+  sigaction (SIGSEGV, &sa, nullptr);
+#else
+  signal (SIGSEGV, handle_sigsegv);
+#endif
+}
+
+/* Handler for SIGSEGV.  */
+
+static void
+handle_sigsegv (int sig)
+{
+  install_handle_sigsegv ();
+
+  if (thread_local_segv_handler == nullptr)
+    abort ();
+  thread_local_segv_handler (sig);
+}
+
+\f
+
 /* The serial event associated with the QUIT flag.  set_quit_flag sets
    this, and check_quit_flag clears it.  Used by interruptible_select
    to be able to do interruptible I/O with no race with the SIGINT
@@ -914,6 +953,8 @@ async_init_signals (void)
   sigtstp_token =
     create_async_signal_handler (async_sigtstp_handler, NULL);
 #endif
+
+  install_handle_sigsegv ();
 }
 
 /* See defs.h.  */
diff --git a/gdb/event-top.h b/gdb/event-top.h
index 1dc7b13d4f8..e844125cbbf 100644
--- a/gdb/event-top.h
+++ b/gdb/event-top.h
@@ -70,4 +70,10 @@ extern void gdb_rl_callback_handler_install (const char *prompt);
    currently installed.  */
 extern void gdb_rl_callback_handler_reinstall (void);
 
+/* The SIGSEGV handler for this thread, or NULL if there is none.  GDB
+   always installs a global SIGSEGV handler, and then lets threads
+   indicate their interest in handling the signal by setting this
+   thread-local variable.  */
+extern thread_local void (*thread_local_segv_handler) (int);
+
 #endif
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 02/11] Defer minimal symbol name-setting
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (8 preceding siblings ...)
  2019-10-01 20:12 ` [PATCH v4 03/11] Add configure check for std::thread Tom Tromey
@ 2019-10-01 20:16 ` Tom Tromey
  2019-10-01 20:16 ` [PATCH v4 06/11] Lock the demangled hash table Tom Tromey
  2019-10-06 22:34 ` [PATCH v4 00/11] Demangle minimal symbol names in worker threads Christian Biesinger via gdb-patches
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:16 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

Currently the demangled name of a minimal symbol is set when creating
the symbol.  However, there is no intrinsic need to do this.  This
patch instead arranges for the demangling to be done just before the
minsym hash tables are filled.  This will be useful in a later patch.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* symtab.h (struct minimal_symbol) <name_set>: New member.
	* minsyms.c (minimal_symbol_reader::record_full): Copy name.
	Don't call symbol_set_names.
	(minimal_symbol_reader::install): Call symbol_set_names.
---
 gdb/ChangeLog |  7 +++++++
 gdb/minsyms.c | 18 +++++++++++++++++-
 gdb/symtab.h  |  4 ++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 83f5d895779..2b259d39c11 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -1106,7 +1106,11 @@ minimal_symbol_reader::record_full (const char *name, int name_len,
   msymbol = &m_msym_bunch->contents[m_msym_bunch_index];
   symbol_set_language (msymbol, language_auto,
 		       &m_objfile->per_bfd->storage_obstack);
-  symbol_set_names (msymbol, name, name_len, copy_name, m_objfile->per_bfd);
+
+  if (copy_name)
+    name = (char *) obstack_copy0 (&m_objfile->per_bfd->storage_obstack,
+				   name, name_len);
+  msymbol->name = name;
 
   SET_MSYMBOL_VALUE_ADDRESS (msymbol, address);
   MSYMBOL_SECTION (msymbol) = section;
@@ -1327,6 +1331,18 @@ minimal_symbol_reader::install ()
       m_objfile->per_bfd->minimal_symbol_count = mcount;
       m_objfile->per_bfd->msymbols = std::move (msym_holder);
 
+      msymbols = m_objfile->per_bfd->msymbols.get ();
+      for (int i = 0; i < mcount; ++i)
+	{
+	  if (!msymbols[i].name_set)
+	    {
+	      symbol_set_names (&msymbols[i], msymbols[i].name,
+				strlen (msymbols[i].name), 0,
+				m_objfile->per_bfd);
+	      msymbols[i].name_set = 1;
+	    }
+	}
+
       build_minimal_symbol_hash_tables (m_objfile);
     }
 }
diff --git a/gdb/symtab.h b/gdb/symtab.h
index 1f0fc62a657..c3918a85af7 100644
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -669,6 +669,10 @@ struct minimal_symbol : public general_symbol_info
      the object file format may not carry that piece of information.  */
   unsigned int has_size : 1;
 
+  /* Non-zero if this symbol ever had its demangled name set (even if
+     it was set to NULL).  */
+  unsigned int name_set : 1;
+
   /* Minimal symbols with the same hash key are kept on a linked
      list.  This is the link.  */
 
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 00/11] Demangle minimal symbol names in worker threads
@ 2019-10-01 20:16 Tom Tromey
  2019-10-01 20:12 ` [PATCH v4 10/11] Add maint set/show max-worker-threads Tom Tromey
                   ` (11 more replies)
  0 siblings, 12 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:16 UTC (permalink / raw)
  To: gdb-patches

This is v4 of my patch series to demangle minimal symbol names in
worker threads.

v3 was here:

    https://sourceware.org/ml/gdb-patches/2019-05/msg00669.html

This version addresses all review comments, and fixes a few problems.
Some significant changes compared to v3:

* Added a patch to switch gdb's m4 files from sinclude to m4_include.

* Arranged to block signals that are needed by gdb in new threads.
  E.g. this prevents a SIGCHLD from arriving in the wrong thread.

* Arranged for the demangler threads to call sigaltstack.

* Changed the API of parallel_for_each to make the sigaltstack patch
  work in a non-convoluted way.  This also makes it simpler to change
  parallel_for_each to run on top of a thread pool later on, should we
  desire.

* Added a patch to use run_on_main_thread in gdb.post_event, as
  requested.

* Removed the ada_decode patch, as a different version of this has
  landed.

Tested on x86-64 Fedora 28.

Tom

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v4 06/11] Lock the demangled hash table
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (9 preceding siblings ...)
  2019-10-01 20:16 ` [PATCH v4 02/11] Defer minimal symbol name-setting Tom Tromey
@ 2019-10-01 20:16 ` Tom Tromey
  2019-10-06 22:34 ` [PATCH v4 00/11] Demangle minimal symbol names in worker threads Christian Biesinger via gdb-patches
  11 siblings, 0 replies; 16+ messages in thread
From: Tom Tromey @ 2019-10-01 20:16 UTC (permalink / raw)
  To: gdb-patches; +Cc: Tom Tromey

This introduces a lock that is used when modifying the demangled hash
table.

gdb/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* symtab.c (demangled_mutex): New global.
	(symbol_set_names): Use a lock_guard.
---
 gdb/ChangeLog |   5 ++
 gdb/symtab.c  | 153 +++++++++++++++++++++++++++++---------------------
 2 files changed, 93 insertions(+), 65 deletions(-)

diff --git a/gdb/symtab.c b/gdb/symtab.c
index 6ea9fc6971e..8adcff7cf2b 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -69,6 +69,9 @@
 #include "arch-utils.h"
 #include <algorithm>
 #include "gdbsupport/pathstuff.h"
+#if CXX_STD_THREAD
+#include <mutex>
+#endif
 
 /* Forward declarations for local functions.  */
 
@@ -710,6 +713,16 @@ symbol_set_language (struct general_symbol_info *gsymbol,
 
 /* Functions to initialize a symbol's mangled name.  */
 
+#if CXX_STD_THREAD
+/* Mutex that is used when modifying or accessing the demangled hash
+   table.  This is a global mutex simply because the only current
+   multi-threaded user of the hash table does not process multiple
+   objfiles in parallel.  The mutex could easily live on the per-BFD
+   object, but this approach avoids using extra memory when it is not
+   needed.  */
+static std::mutex demangled_mutex;
+#endif
+
 /* Objects of this type are stored in the demangled name hash table.  */
 struct demangled_name_entry
 {
@@ -839,9 +852,6 @@ symbol_set_names (struct general_symbol_info *gsymbol,
       return;
     }
 
-  if (per_bfd->demangled_names_hash == NULL)
-    create_demangled_names_hash (per_bfd);
-
   if (linkage_name[len] != '\0')
     {
       char *alloc_name;
@@ -855,71 +865,84 @@ symbol_set_names (struct general_symbol_info *gsymbol,
   else
     linkage_name_copy = linkage_name;
 
-  entry.mangled = linkage_name_copy;
-  slot = ((struct demangled_name_entry **)
-	  htab_find_slot (per_bfd->demangled_names_hash.get (),
-			  &entry, INSERT));
-
-  /* If this name is not in the hash table, add it.  */
-  if (*slot == NULL
-      /* A C version of the symbol may have already snuck into the table.
-	 This happens to, e.g., main.init (__go_init_main).  Cope.  */
-      || (gsymbol->language == language_go
-	  && (*slot)->demangled[0] == '\0'))
-    {
-      char *demangled_name_ptr
-	= symbol_find_demangled_name (gsymbol, linkage_name_copy);
-      gdb::unique_xmalloc_ptr<char> demangled_name (demangled_name_ptr);
-      int demangled_len = demangled_name ? strlen (demangled_name.get ()) : 0;
-
-      /* Suppose we have demangled_name==NULL, copy_name==0, and
-	 linkage_name_copy==linkage_name.  In this case, we already have the
-	 mangled name saved, and we don't have a demangled name.  So,
-	 you might think we could save a little space by not recording
-	 this in the hash table at all.
+  struct demangled_name_entry *found_entry;
+
+  {
+#if CXX_STD_THREAD
+    std::lock_guard<std::mutex> guard (demangled_mutex);
+#endif
+
+    if (per_bfd->demangled_names_hash == NULL)
+      create_demangled_names_hash (per_bfd);
+
+    entry.mangled = linkage_name_copy;
+    slot = ((struct demangled_name_entry **)
+	    htab_find_slot (per_bfd->demangled_names_hash.get (),
+			    &entry, INSERT));
+
+    /* If this name is not in the hash table, add it.  */
+    if (*slot == NULL
+	/* A C version of the symbol may have already snuck into the table.
+	   This happens to, e.g., main.init (__go_init_main).  Cope.  */
+	|| (gsymbol->language == language_go
+	    && (*slot)->demangled[0] == '\0'))
+      {
+	char *demangled_name_ptr
+	  = symbol_find_demangled_name (gsymbol, linkage_name_copy);
+	gdb::unique_xmalloc_ptr<char> demangled_name (demangled_name_ptr);
+	int demangled_len = demangled_name ? strlen (demangled_name.get ()) : 0;
+
+	/* Suppose we have demangled_name==NULL, copy_name==0, and
+	   linkage_name_copy==linkage_name.  In this case, we already have the
+	   mangled name saved, and we don't have a demangled name.  So,
+	   you might think we could save a little space by not recording
+	   this in the hash table at all.
 	 
-	 It turns out that it is actually important to still save such
-	 an entry in the hash table, because storing this name gives
-	 us better bcache hit rates for partial symbols.  */
-      if (!copy_name && linkage_name_copy == linkage_name)
-	{
-	  *slot
-	    = ((struct demangled_name_entry *)
-	       obstack_alloc (&per_bfd->storage_obstack,
-			      offsetof (struct demangled_name_entry, demangled)
-			      + demangled_len + 1));
-	  (*slot)->mangled = linkage_name;
-	}
-      else
-	{
-	  char *mangled_ptr;
-
-	  /* If we must copy the mangled name, put it directly after
-	     the demangled name so we can have a single
-	     allocation.  */
-	  *slot
-	    = ((struct demangled_name_entry *)
-	       obstack_alloc (&per_bfd->storage_obstack,
-			      offsetof (struct demangled_name_entry, demangled)
-			      + len + demangled_len + 2));
-	  mangled_ptr = &((*slot)->demangled[demangled_len + 1]);
-	  strcpy (mangled_ptr, linkage_name_copy);
-	  (*slot)->mangled = mangled_ptr;
-	}
-      (*slot)->language = gsymbol->language;
+	   It turns out that it is actually important to still save such
+	   an entry in the hash table, because storing this name gives
+	   us better bcache hit rates for partial symbols.  */
+	if (!copy_name && linkage_name_copy == linkage_name)
+	  {
+	    *slot
+	      = ((struct demangled_name_entry *)
+		 obstack_alloc (&per_bfd->storage_obstack,
+				offsetof (struct demangled_name_entry, demangled)
+				+ demangled_len + 1));
+	    (*slot)->mangled = linkage_name;
+	  }
+	else
+	  {
+	    char *mangled_ptr;
+
+	    /* If we must copy the mangled name, put it directly after
+	       the demangled name so we can have a single
+	       allocation.  */
+	    *slot
+	      = ((struct demangled_name_entry *)
+		 obstack_alloc (&per_bfd->storage_obstack,
+				offsetof (struct demangled_name_entry, demangled)
+				+ len + demangled_len + 2));
+	    mangled_ptr = &((*slot)->demangled[demangled_len + 1]);
+	    strcpy (mangled_ptr, linkage_name_copy);
+	    (*slot)->mangled = mangled_ptr;
+	  }
+	(*slot)->language = gsymbol->language;
 
-      if (demangled_name != NULL)
-	strcpy ((*slot)->demangled, demangled_name.get ());
-      else
-	(*slot)->demangled[0] = '\0';
-    }
-  else if (gsymbol->language == language_unknown
-	   || gsymbol->language == language_auto)
-    gsymbol->language = (*slot)->language;
+	if (demangled_name != NULL)
+	  strcpy ((*slot)->demangled, demangled_name.get ());
+	else
+	  (*slot)->demangled[0] = '\0';
+      }
+    else if (gsymbol->language == language_unknown
+	     || gsymbol->language == language_auto)
+      gsymbol->language = (*slot)->language;
+
+    found_entry = *slot;
+  }
 
-  gsymbol->name = (*slot)->mangled;
-  if ((*slot)->demangled[0] != '\0')
-    symbol_set_demangled_name (gsymbol, (*slot)->demangled,
+  gsymbol->name = found_entry->mangled;
+  if (found_entry->demangled[0] != '\0')
+    symbol_set_demangled_name (gsymbol, found_entry->demangled,
 			       &per_bfd->storage_obstack);
   else
     symbol_set_demangled_name (gsymbol, NULL, &per_bfd->storage_obstack);
-- 
2.17.2

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v4 10/11] Add maint set/show max-worker-threads
  2019-10-01 20:12 ` [PATCH v4 10/11] Add maint set/show max-worker-threads Tom Tromey
@ 2019-10-02 14:54   ` Eli Zaretskii
  0 siblings, 0 replies; 16+ messages in thread
From: Eli Zaretskii @ 2019-10-02 14:54 UTC (permalink / raw)
  To: Tom Tromey; +Cc: gdb-patches

> From: Tom Tromey <tom@tromey.com>
> Cc: Tom Tromey <tom@tromey.com>
> Date: Tue,  1 Oct 2019 14:12:26 -0600
> 
> This adds maint commands to control the maximum number of worker
> threads that gdb can use.
> 
> gdb/ChangeLog
> 2019-10-01  Tom Tromey  <tom@tromey.com>
> 
> 	* NEWS: Add entry.
> 	* maint.c (_initialize_maint_cmds): Add "max-worker-threads" maint
> 	commands.
> 
> gdb/doc/ChangeLog
> 2019-10-01  Tom Tromey  <tom@tromey.com>
> 
> 	* gdb.texinfo (Maintenance Commands): Document new maint
> 	commands.

The documentation parts are OK, thanks.

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v4 00/11] Demangle minimal symbol names in worker threads
  2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
                   ` (10 preceding siblings ...)
  2019-10-01 20:16 ` [PATCH v4 06/11] Lock the demangled hash table Tom Tromey
@ 2019-10-06 22:34 ` Christian Biesinger via gdb-patches
  2019-10-07  0:58   ` Tom Tromey
  11 siblings, 1 reply; 16+ messages in thread
From: Christian Biesinger via gdb-patches @ 2019-10-06 22:34 UTC (permalink / raw)
  To: Tom Tromey; +Cc: gdb-patches

On Tue, Oct 1, 2019 at 3:16 PM Tom Tromey <tom@tromey.com> wrote:
>
> This is v4 of my patch series to demangle minimal symbol names in
> worker threads.
>
> v3 was here:
>
>     https://sourceware.org/ml/gdb-patches/2019-05/msg00669.html
>
> This version addresses all review comments, and fixes a few problems.
> Some significant changes compared to v3:
>
> * Added a patch to switch gdb's m4 files from sinclude to m4_include.

This could probably land separately, it seems independent of the rest.

Otherwise, as you mentioned on IRC, it may make sense to land at least
the first of my patches together with this one because my patch
basically reverts the mutex change in symbol_set_names.

I am really excited about this work on faster symbol loading!

Christian

> * Arranged to block signals that are needed by gdb in new threads.
>   E.g. this prevents a SIGCHLD from arriving in the wrong thread.
>
> * Arranged for the demangler threads to call sigaltstack.
>
> * Changed the API of parallel_for_each to make the sigaltstack patch
>   work in a non-convoluted way.  This also makes it simpler to change
>   parallel_for_each to run on top of a thread pool later on, should we
>   desire.
>
> * Added a patch to use run_on_main_thread in gdb.post_event, as
>   requested.
>
> * Removed the ada_decode patch, as a different version of this has
>   landed.
>
> Tested on x86-64 Fedora 28.
>
> Tom
>
>

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v4 00/11] Demangle minimal symbol names in worker threads
  2019-10-06 22:34 ` [PATCH v4 00/11] Demangle minimal symbol names in worker threads Christian Biesinger via gdb-patches
@ 2019-10-07  0:58   ` Tom Tromey
  2019-10-08  2:01     ` Christian Biesinger via gdb-patches
  0 siblings, 1 reply; 16+ messages in thread
From: Tom Tromey @ 2019-10-07  0:58 UTC (permalink / raw)
  To: Christian Biesinger; +Cc: Tom Tromey, gdb-patches

>>>>> "Christian" == Christian Biesinger <cbiesinger@google.com> writes:

Christian> Otherwise, as you mentioned on IRC, it may make sense to land at least
Christian> the first of my patches together with this one because my patch
Christian> basically reverts the mutex change in symbol_set_names.

Yeah, I think so.  I have yet to read your latest patches, but I
definitely don't plan to land anything until then.  I think we may want
to move to thread pools as well before moving forward, because that will
affect the "maint" command that is exposed.

Tom

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v4 00/11] Demangle minimal symbol names in worker threads
  2019-10-07  0:58   ` Tom Tromey
@ 2019-10-08  2:01     ` Christian Biesinger via gdb-patches
  0 siblings, 0 replies; 16+ messages in thread
From: Christian Biesinger via gdb-patches @ 2019-10-08  2:01 UTC (permalink / raw)
  To: Tom Tromey; +Cc: gdb-patches

On Sun, Oct 6, 2019 at 7:58 PM Tom Tromey <tom@tromey.com> wrote:
>
> >>>>> "Christian" == Christian Biesinger <cbiesinger@google.com> writes:
>
> Christian> Otherwise, as you mentioned on IRC, it may make sense to land at least
> Christian> the first of my patches together with this one because my patch
> Christian> basically reverts the mutex change in symbol_set_names.
>
> Yeah, I think so.  I have yet to read your latest patches, but I
> definitely don't plan to land anything until then.  I think we may want
> to move to thread pools as well before moving forward, because that will
> affect the "maint" command that is exposed.

Hm, I'm not sure that needs to be part of the same patchset (since for
now nothing else uses threads). But I did try implementing a thread
pool in https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=shortlog;h=refs/heads/users/cbiesinger/threadpool.
Unfortunately it seems to be a bit slower... I must've implemented it
wrong. My initial impression is that maybe not all threads are used
equally?

(The current version of that threadpool patch does not support
changing the number of threads, so that would have to be changed if
nothing else)

Christian

^ permalink raw reply	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2019-10-08  2:01 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-10-01 20:16 [PATCH v4 00/11] Demangle minimal symbol names in worker threads Tom Tromey
2019-10-01 20:12 ` [PATCH v4 10/11] Add maint set/show max-worker-threads Tom Tromey
2019-10-02 14:54   ` Eli Zaretskii
2019-10-01 20:12 ` [PATCH v4 04/11] Add RAII class for blocking gdb signals Tom Tromey
2019-10-01 20:12 ` [PATCH v4 09/11] Demangle minsyms in parallel Tom Tromey
2019-10-01 20:12 ` [PATCH v4 08/11] Introduce thread-safe way to handle SIGSEGV Tom Tromey
2019-10-01 20:12 ` [PATCH v4 01/11] Use m4_include, not sinclude in .m4 files Tom Tromey
2019-10-01 20:12 ` [PATCH v4 11/11] Use run_on_main_thread in gdb.post_event Tom Tromey
2019-10-01 20:12 ` [PATCH v4 07/11] Introduce run_on_main_thread Tom Tromey
2019-10-01 20:12 ` [PATCH v4 05/11] Introduce alternate_signal_stack RAII class Tom Tromey
2019-10-01 20:12 ` [PATCH v4 03/11] Add configure check for std::thread Tom Tromey
2019-10-01 20:16 ` [PATCH v4 02/11] Defer minimal symbol name-setting Tom Tromey
2019-10-01 20:16 ` [PATCH v4 06/11] Lock the demangled hash table Tom Tromey
2019-10-06 22:34 ` [PATCH v4 00/11] Demangle minimal symbol names in worker threads Christian Biesinger via gdb-patches
2019-10-07  0:58   ` Tom Tromey
2019-10-08  2:01     ` Christian Biesinger via gdb-patches

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