[PATCH 07/25] Thread options & clone events (native Linux)

[Pedro Alves <pedro@palves.net>]

This commit teaches the native Linux target about the GDB_TO_CLONE
thread option.  It's actually simpler to just continue reporting all
clone events unconditionally to the core.  There's never any harm in
reporting a clone event when the option is disabled.  All we need to
do is copy the thread options from clone parent to clone child, and
report support for the option, otherwise GDB falls back to use
target_thread_events().

Change-Id: If271f20320d864f074d8ac0d531cc1a323da847f
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=19675
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27830
---
 gdb/linux-nat.c | 26 +++++++++++++++++++++++++-
 gdb/linux-nat.h |  3 +++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 138632667e4..a446a755242 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1863,6 +1863,8 @@ linux_nat_target::follow_clone (ptid_t child_ptid)
   lwp_info *new_lp = add_lwp (child_ptid);
   new_lp->stopped = 1;
 
+  thread_info *new_thr = nullptr;
+
   /* If the thread_db layer is active, let it record the user
      level thread id and status, and add the thread to GDB's
      list.  */
@@ -1871,12 +1873,19 @@ linux_nat_target::follow_clone (ptid_t child_ptid)
       /* The process is not using thread_db.  Add the LWP to
 	 GDB's list.  */
       target_post_attach (new_lp->ptid.lwp ());
-      add_thread (linux_target, new_lp->ptid);
+      new_thr = add_thread (linux_target, new_lp->ptid);
     }
+  else
+    new_thr = find_thread_ptid (linux_target, new_lp->ptid);
+
+  gdb_assert (new_thr != nullptr);
 
   /* We just created NEW_LP so it cannot yet contain STATUS.  */
   gdb_assert (new_lp->status == 0);
 
+  /* Copy parent options to the child.  */
+  new_thr->set_thread_options (inferior_thread ()->thread_options ());
+
   if (!pull_pid_from_list (&stopped_pids, child_ptid.lwp (), &new_lp->status))
     internal_error (__FILE__, __LINE__, _("no saved status for clone lwp"));
 
@@ -4397,6 +4406,21 @@ linux_nat_target::thread_events (int enable)
   report_thread_events = enable;
 }
 
+bool
+linux_nat_target::supports_set_thread_options (gdb_thread_options options)
+{
+  constexpr gdb_thread_options supported_options = GDB_TO_CLONE;
+  return ((options & supported_options) == options);
+}
+
+void
+linux_nat_target::set_thread_options (thread_info *thr,
+				      gdb_thread_options options)
+{
+  /* Nothing to do.  target_set_thread_options already recorded the
+     options in THR.  */
+}
+
 linux_nat_target::linux_nat_target ()
 {
   /* We don't change the stratum; this target will sit at
diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
index 683173dbd38..b848c9bac6a 100644
--- a/gdb/linux-nat.h
+++ b/gdb/linux-nat.h
@@ -82,6 +82,9 @@ class linux_nat_target : public inf_ptrace_target
 
   void thread_events (int) override;
 
+  bool supports_set_thread_options (gdb_thread_options options) override;
+  void set_thread_options (thread_info *, gdb_thread_options) override;
+
   bool can_async_p () override;
 
   bool supports_non_stop () override;
-- 
2.36.0