[PATCH] add notify_count for de_thread

From: Manfred Spraul <manfred@colorfullife.com>

de_thread is called by exec to kill all threads in the thread group except
the threads required for exec.

The waiting is implemented by waiting for a wakeup from __exit_signal: If
the reference count is less or equal to 2, then the waiter is woken up.  If
exec is called by a non-leader thread, then two threads are required for
exec.

But if a thread group leader calls exec, then only one thread is required
for exec.  Thus the hardcoded "2" leads to a superfluous wakeup.  The patch
fixes that by adding a "notify_count" field to the signal structure.

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 75e6e1b5b363..003195629026 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -245,7 +245,13 @@ struct signal_struct {
 	/* thread group exit support */
 	int			group_exit;
 	int			group_exit_code;
+	/* overloaded:
+	 * - notify group_exit_task when ->count is equal to notify_count
+	 * - everyone except group_exit_task is stopped during signal delivery
+	 *   of fatal signals, group_exit_task processes the signal.
+	 */
 	struct task_struct	*group_exit_task;
+	int			notify_count;
 
 	/* thread group stop support, overloads group_exit_code too */
 	int			group_stop_count;