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Initialize last_resume_kind for remote fork child 

This patch fixes some intermittent test failures in
gdb.base/foll-vfork.exp where a vfork child would be (incorrectly)
resumed when handling the vfork event.  In this case the result
was a subsequent event reported to the client side as a SIGTRAP
delivered to the as-yet-unknown child thread.

The new thread was resumed (incorrectly) in linux-low.c when
resume_stopped_resumed_lwps was called from
linux_wait_for_event_filtered after the vfork event had been
handled in handle_extended_wait.

Gdbserver/linux-low.c's add_thread function creates threads with
last_resume_kind == resume_continue by default.  This field is
used by resume_stopped_resumed_lwps to decide whether to perform
the resume:

static void
resume_stopped_resumed_lwps (struct inferior_list_entry *entry) {
  struct thread_info *thread = (struct thread_info *) entry;
  struct lwp_info *lp = get_thread_lwp (thread);

  if (lp->stopped
      && !lp->status_pending_p
      && thread->last_resume_kind != resume_stop
      && thread->last_status.kind == TARGET_WAITKIND_IGNORE)
    {

So the fix is to make sure to set thread->last_resume_kind to
resume_stop.  Here we do that for new fork children in
gdbserver/linux-low.c:handle_extended_wait.

In addition, it seemed prudent to initialize lwp_info.status_pending_p
for the new fork child.  I also rearranged the initialization code
so that all of the lwp_info initialization was together, rather than
intermixed with thread_info and process_info initialization.

Tested native, native-gdbserver, native-extended-gdbserver on
x86_64 GNU/Linux.

gdb/gdbserver/

	* linux-low.c (handle_extended_wait): Initialize
	thread_info.last_resume_kind for new fork children.
This commit is contained in:
Don Breazeal 2015-05-28 13:12:01 -07:00
parent 8dd06f7a89
commit bfacd19d64
2 changed files with 10 additions and 1 deletions
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5
gdb/gdbserver/ChangeLog
View File

@ -1,3 +1,8 @@
2015-05-28 Don Breazeal <donb@codesourcery.com>
* linux-low.c (handle_extended_wait): Initialize
thread_info.last_resume_kind for new fork children.
2015-05-15 Pedro Alves <palves@redhat.com>
* target.h (target_handle_new_gdb_connection): Rewrite using if

6
gdb/gdbserver/linux-low.c
View File

@ -457,6 +457,7 @@ handle_extended_wait (struct lwp_info *event_lwp, int wstat)
struct process_info *parent_proc;
struct process_info *child_proc;
struct lwp_info *child_lwp;
struct thread_info *child_thr;
struct target_desc *tdesc;
ptid = ptid_build (new_pid, new_pid, 0);
@ -479,6 +480,10 @@ handle_extended_wait (struct lwp_info *event_lwp, int wstat)
child_lwp = add_lwp (ptid);
gdb_assert (child_lwp != NULL);
child_lwp->stopped = 1;
child_lwp->must_set_ptrace_flags = 1;
child_lwp->status_pending_p = 0;
child_thr = get_lwp_thread (child_lwp);
child_thr->last_resume_kind = resume_stop;
parent_proc = get_thread_process (event_thr);
child_proc->attached = parent_proc->attached;
clone_all_breakpoints (&child_proc->breakpoints,
@ -488,7 +493,6 @@ handle_extended_wait (struct lwp_info *event_lwp, int wstat)
tdesc = xmalloc (sizeof (struct target_desc));
copy_target_description (tdesc, parent_proc->tdesc);
child_proc->tdesc = tdesc;
child_lwp->must_set_ptrace_flags = 1;
/* Clone arch-specific process data. */
if (the_low_target.new_fork != NULL)