exit: avoid sig->count in de_thread/__exit_signal synchronization

de_thread() and __exit_signal() use signal_struct->count/notify_count for
synchronization.  We can simplify the code and use ->notify_count only.
Instead of comparing these two counters, we can change de_thread() to set
->notify_count = nr_of_sub_threads, then change __exit_signal() to
dec-and-test this counter and notify group_exit_task.

Note that __exit_signal() checks "notify_count > 0" just for symmetry with
exit_notify(), we could just check it is != 0.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 59a104c673f7..9220967f4256 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -97,7 +97,7 @@ static void __exit_signal(struct task_struct *tsk)
                  * If there is any task waiting for the group exit
                  * then notify it:
                  */
-                if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
+                if (sig->notify_count > 0 && !--sig->notify_count)
                         wake_up_process(sig->group_exit_task);
 
                 if (tsk == sig->curr_target)