[PATCH] New --enable-threading configure option to control use of threads in GDB/GDBserver

[PATCH] New --enable-threading configure option to control use of threads in GDB/GDBserver

[Luis Machado]

Add the --enable-threading configure option so multithreading can be disabled
at configure time. This is useful for statically-linked builds of
GDB/GDBserver, since the thread library doesn't play well with that setup.

If you try to run a statically-linked GDB built with threading, it will crash
when setting up the number of worker threads.

This new option is also convenient when debugging GDB in a system with lots of
threads, where the thread discovery code in GDB will emit too many messages,
like so:

[New Thread 0xfffff74d3a50 (LWP 2625599)]

If you have X threads, that message will be repeated X times.

The default for --enable-threading is "yes".

OK?
---
 gdb/configure        | 24 +++++++++++++++++++++++-
 gdbserver/configure  | 24 +++++++++++++++++++++++-
 gdbsupport/common.m4 | 22 +++++++++++++++++++---
 gdbsupport/configure | 24 +++++++++++++++++++++++-
 4 files changed, 88 insertions(+), 6 deletions(-)

diff --git a/gdb/configure b/gdb/configure
index 448167f3c6d..d13ab374050 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -910,6 +910,7 @@ with_python
 with_python_libdir
 with_guile
 enable_source_highlight
+enable_threading
 with_intel_pt
 with_libipt_prefix
 with_libipt_type
@@ -1597,6 +1598,8 @@ Optional Features:
   --disable-rpath         do not hardcode runtime library paths
   --enable-source-highlight
                           enable source-highlight for source listings
+  --enable-threading      include support for parallel processing of data
+                          (yes/no)
   --enable-werror         treat compile warnings as errors
   --enable-build-warnings enable build-time compiler warnings if gcc is used
   --enable-gdb-build-warnings
@@ -14065,6 +14068,22 @@ fi
 done
 
 
+  # ----------------------- #
+  # Check for threading.    #
+  # ----------------------- #
+
+  # Check whether --enable-threading was given.
+if test "${enable_threading+set}" = set; then :
+  enableval=$enable_threading; case "$enableval" in
+    yes) want_threading=yes ;;
+    no) want_threading=no ;;
+    *) as_fn_error $? "bad value $enableval for threading" "$LINENO" 5 ;;
+    esac
+else
+  want_threading=yes
+fi
+
+
   # Check for std::thread.  This does not work on some platforms, like
   # mingw and DJGPP.
   ac_ext=cpp
@@ -14762,10 +14781,13 @@ done
     LIBS="$save_LIBS"
     CXXFLAGS="$save_CXXFLAGS"
   fi
-  if test "$gdb_cv_cxx_std_thread" = "yes"; then
+
+  if test "$want_threading" = "yes"; then
+    if test "$gdb_cv_cxx_std_thread" = "yes"; then
 
 $as_echo "#define CXX_STD_THREAD 1" >>confdefs.h
 
+    fi
   fi
   ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
diff --git a/gdbserver/configure b/gdbserver/configure
index 8e2bd4e1ba5..d90135be45c 100755
--- a/gdbserver/configure
+++ b/gdbserver/configure
@@ -746,6 +746,7 @@ ac_user_opts='
 enable_option_checking
 enable_maintainer_mode
 enable_largefile
+enable_threading
 with_intel_pt
 with_gnu_ld
 enable_rpath
@@ -1396,6 +1397,8 @@ Optional Features:
                           enable make rules and dependencies not useful (and
                           sometimes confusing) to the casual installer
   --disable-largefile     omit support for large files
+  --enable-threading      include support for parallel processing of data
+                          (yes/no)
   --disable-rpath         do not hardcode runtime library paths
   --enable-unit-tests     Enable the inclusion of unit tests when compiling
                           GDB
@@ -7264,6 +7267,22 @@ fi
 done
 
 
+  # ----------------------- #
+  # Check for threading.    #
+  # ----------------------- #
+
+  # Check whether --enable-threading was given.
+if test "${enable_threading+set}" = set; then :
+  enableval=$enable_threading; case "$enableval" in
+    yes) want_threading=yes ;;
+    no) want_threading=no ;;
+    *) as_fn_error $? "bad value $enableval for threading" "$LINENO" 5 ;;
+    esac
+else
+  want_threading=yes
+fi
+
+
   # Check for std::thread.  This does not work on some platforms, like
   # mingw and DJGPP.
   ac_ext=cpp
@@ -7961,10 +7980,13 @@ done
     LIBS="$save_LIBS"
     CXXFLAGS="$save_CXXFLAGS"
   fi
-  if test "$gdb_cv_cxx_std_thread" = "yes"; then
+
+  if test "$want_threading" = "yes"; then
+    if test "$gdb_cv_cxx_std_thread" = "yes"; then
 
 $as_echo "#define CXX_STD_THREAD 1" >>confdefs.h
 
+    fi
   fi
   ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
diff --git a/gdbsupport/common.m4 b/gdbsupport/common.m4
index 81e7c75f51d..430d66b5558 100644
--- a/gdbsupport/common.m4
+++ b/gdbsupport/common.m4
@@ -76,6 +76,19 @@ AC_DEFUN([GDB_AC_COMMON], [
   # Define HAVE_KINFO_GETFILE if kinfo_getfile is available.
   AC_CHECK_FUNCS(kinfo_getfile)
 
+  # ----------------------- #
+  # Check for threading.    #
+  # ----------------------- #
+
+  AC_ARG_ENABLE(threading,
+    AS_HELP_STRING([--enable-threading], [include support for parallel processing of data (yes/no)]),
+    [case "$enableval" in
+    yes) want_threading=yes ;;
+    no) want_threading=no ;;
+    *) AC_MSG_ERROR([bad value $enableval for threading]) ;;
+    esac],
+    [want_threading=yes])
+
   # Check for std::thread.  This does not work on some platforms, like
   # mingw and DJGPP.
   AC_LANG_PUSH([C++])
@@ -101,9 +114,12 @@ AC_DEFUN([GDB_AC_COMMON], [
     LIBS="$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.])
+
+  if test "$want_threading" = "yes"; then
+    if test "$gdb_cv_cxx_std_thread" = "yes"; then
+      AC_DEFINE(CXX_STD_THREAD, 1,
+		[Define to 1 if std::thread works.])
+    fi
   fi
   AC_LANG_POP
 
diff --git a/gdbsupport/configure b/gdbsupport/configure
index 0b4e81a9c16..8b4cb7e098d 100755
--- a/gdbsupport/configure
+++ b/gdbsupport/configure
@@ -767,6 +767,7 @@ enable_silent_rules
 enable_dependency_tracking
 enable_plugins
 enable_largefile
+enable_threading
 with_intel_pt
 with_gnu_ld
 enable_rpath
@@ -1419,6 +1420,8 @@ Optional Features:
                           speeds up one-time build
   --enable-plugins        Enable support for plugins
   --disable-largefile     omit support for large files
+  --enable-threading      include support for parallel processing of data
+                          (yes/no)
   --disable-rpath         do not hardcode runtime library paths
   --enable-unit-tests     Enable the inclusion of unit tests when compiling
                           GDB
@@ -8277,6 +8280,22 @@ fi
 done
 
 
+  # ----------------------- #
+  # Check for threading.    #
+  # ----------------------- #
+
+  # Check whether --enable-threading was given.
+if test "${enable_threading+set}" = set; then :
+  enableval=$enable_threading; case "$enableval" in
+    yes) want_threading=yes ;;
+    no) want_threading=no ;;
+    *) as_fn_error $? "bad value $enableval for threading" "$LINENO" 5 ;;
+    esac
+else
+  want_threading=yes
+fi
+
+
   # Check for std::thread.  This does not work on some platforms, like
   # mingw and DJGPP.
   ac_ext=cpp
@@ -8974,10 +8993,13 @@ done
     LIBS="$save_LIBS"
     CXXFLAGS="$save_CXXFLAGS"
   fi
-  if test "$gdb_cv_cxx_std_thread" = "yes"; then
+
+  if test "$want_threading" = "yes"; then
+    if test "$gdb_cv_cxx_std_thread" = "yes"; then
 
 $as_echo "#define CXX_STD_THREAD 1" >>confdefs.h
 
+    fi
   fi
   ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
-- 
2.25.1

Re: [PATCH] New --enable-threading configure option to control use of threads in GDB/GDBserver

[Tom Tromey]

>>>>> "Luis" == Luis Machado via Gdb-patches <gdb-patches@sourceware.org> writes:

Luis> Add the --enable-threading configure option so multithreading can be disabled
Luis> at configure time. This is useful for statically-linked builds of
Luis> GDB/GDBserver, since the thread library doesn't play well with that setup.

This is ok.

thanks,
Tom

Re: [PATCH] New --enable-threading configure option to control use of threads in GDB/GDBserver

[Luis Machado]

On 12/7/21 3:51 PM, Tom Tromey wrote:
>>>>>> "Luis" == Luis Machado via Gdb-patches <gdb-patches@sourceware.org> writes:
> 
> Luis> Add the --enable-threading configure option so multithreading can be disabled
> Luis> at configure time. This is useful for statically-linked builds of
> Luis> GDB/GDBserver, since the thread library doesn't play well with that setup.
> 
> This is ok.
> 
> thanks,
> Tom
> 

Thanks. As I was going to push this, I noticed I forgot to add a NEWS 
entry to make it more obvious this option exists.

Here's what I plan to push alongside this patch:

diff --git a/gdb/NEWS b/gdb/NEWS
index 13b66286876..3f78ace82bb 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,17 @@

  *** Changes since GDB 11

+* Configure changes
+
+--enable-threading
+
+  Enable or disable multithreaded symbol loading.  This is enabled
+  by default, but passing --disable-threading or --enable-threading=no
+  to configure will disable it.
+
+  Disabling this can cause a performance penalty when there are a lot of
+  symbols to load, but is useful for debugging purposes.
+
  * New commands

Re: [PATCH] New --enable-threading configure option to control use of threads in GDB/GDBserver

[Eli Zaretskii]

> Cc: Eli Zaretskii <eliz@gnu.org>
> From: Luis Machado <luis.machado@linaro.org>
> Date: Wed, 15 Dec 2021 14:17:55 -0300
> 
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 13b66286876..3f78ace82bb 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -3,6 +3,17 @@
> 
>   *** Changes since GDB 11
> 
> +* Configure changes
> +
> +--enable-threading
> +
> +  Enable or disable multithreaded symbol loading.  This is enabled
> +  by default, but passing --disable-threading or --enable-threading=no
> +  to configure will disable it.
> +
> +  Disabling this can cause a performance penalty when there are a lot of
> +  symbols to load, but is useful for debugging purposes.
> +
>   * New commands

Thanks, this is OK.

Re: [PATCH] New --enable-threading configure option to control use of threads in GDB/GDBserver

[Luis Machado]

On 12/15/21 4:27 PM, Eli Zaretskii wrote:
>> Cc: Eli Zaretskii <eliz@gnu.org>
>> From: Luis Machado <luis.machado@linaro.org>
>> Date: Wed, 15 Dec 2021 14:17:55 -0300
>>
>> diff --git a/gdb/NEWS b/gdb/NEWS
>> index 13b66286876..3f78ace82bb 100644
>> --- a/gdb/NEWS
>> +++ b/gdb/NEWS
>> @@ -3,6 +3,17 @@
>>
>>    *** Changes since GDB 11
>>
>> +* Configure changes
>> +
>> +--enable-threading
>> +
>> +  Enable or disable multithreaded symbol loading.  This is enabled
>> +  by default, but passing --disable-threading or --enable-threading=no
>> +  to configure will disable it.
>> +
>> +  Disabling this can cause a performance penalty when there are a lot of
>> +  symbols to load, but is useful for debugging purposes.
>> +
>>    * New commands
> 
> Thanks, this is OK.
> 

Pushed now.