exit: avoid sig->count in de_thread/__exit_signal synchronization (d344193a) · Commits · 戴 / test

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>

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)

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