[PATCH 3/3] PR remote/19496, timeout in forking-threads-plus-bkpt

[Don Breazeal <donb at codesourcery dot com>]

This patch addresses a failure in
gdb.threads/forking-threads-plus-breakpoint.exp:

FAIL: gdb.threads/forking-threads-plus-breakpoint.exp: cond_bp_target=1:
detach_on_fork=on: inferior 1 exited (timeout)

Cause:
A fork event was reported to GDB before GDB knew about the parent thread,
followed immediately by a breakpoint event in a different thread.  The
parent thread was subsequently added via remote_notice_new_inferior in
process_stop_reply, but when the thread was added the thread_info.state
was set to THREAD_STOPPED.  The fork event was then handled correctly,
but when the fork parent was resumed via a call to keep_going, the state
was unchanged.

The breakpoint event was then handled, which caused all the non-breakpoint
threads to be stopped.  When the breakpoint thread was resumed, all the
non-breakpoint threads were resumed via infrun.c:restart_threads.  Our old
fork parent wasn't restarted, because it still had thread_info.state set to
THREAD_STOPPED.  Ultimately the program under debug hung waiting for a
pthread_join while the old fork parent was stopped forever by GDB.

Fix:
Add a call to set_running just before resuming the fork parent in
infrun.c:handle_inferior_event_1.  The call could be put elsewhere
(e.g. in keep_going) but this approach makes the change for the case
of resuming after a fork event, without potential side-effects for
other cases where keep_going is called.

Tested on x86_64 Linux and Nios II Linux target with x86 Linux host.

Thanks,
--Don

gdb/ChangeLog:
2016-01-27  Don Breazeal  <donb@codesourcery.com>

	PR remote/19496
	* infrun.c (handle_inferior_event_1): Call set_running before
	resuming.

---
 gdb/infrun.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 15210c9..e324864 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -5232,7 +5232,13 @@ Cannot fill $_exitsignal with the correct signal number.\n"));
 	  ecs->ptid = inferior_ptid;
 
 	  if (should_resume)
-	    keep_going (ecs);
+	    {
+	      /* Make sure the thread is marked as running.  If the event
+		 occurred in the thread before we added it, it may have
+		 never been marked running.  */
+	      set_running (inferior_ptid, 1);
+	      keep_going (ecs);
+	    }
 	  else
 	    stop_waiting (ecs);
 	  return;
-- 
1.8.1.1