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Commit d344193a authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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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: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarRoland McGrath <roland@redhat.com>
Cc: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 09faef11

fs/exec.c

+5 −6
Original line number Diff line number Diff line
@@ -768,7 +768,6 @@ static int de_thread(struct task_struct *tsk) 
	struct signal_struct *sig = tsk->signal;

	struct sighand_struct *oldsighand = tsk->sighand;

	spinlock_t *lock = &oldsighand->siglock;

	int count;



	if (thread_group_empty(tsk))

		goto no_thread_group;
@@ -785,13 +784,13 @@ static int de_thread(struct task_struct *tsk) 
		spin_unlock_irq(lock);

		return -EAGAIN;

	}



	sig->group_exit_task = tsk;

	zap_other_threads(tsk);

	sig->notify_count = zap_other_threads(tsk);

	if (!thread_group_leader(tsk))

		sig->notify_count--;



	/* Account for the thread group leader hanging around: */

	count = thread_group_leader(tsk) ? 1 : 2;

	sig->notify_count = count;

	while (atomic_read(&sig->count) > count) {

	while (sig->notify_count) {

		__set_current_state(TASK_UNINTERRUPTIBLE);

		spin_unlock_irq(lock);

		schedule();

kernel/exit.c

+1 −1
Original line number Diff line number Diff line
@@ -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)