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Commit 2d89c929 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Linus Torvalds
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[PATCH] Simpler signal-exit concurrency handling 



Some simplification in checking signal delivery against concurrent exit.
Instead of using get_task_struct_rcu(), which increments the task_struct
reference count, check the reference count after acquiring sighand lock.

Signed-off-by: default avatar"Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e56d0903

kernel/signal.c

+6 −5
Original line number Diff line number Diff line
@@ -1102,18 +1102,19 @@ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p) 


retry:

	ret = check_kill_permission(sig, info, p);

	if (!ret && sig && (sp = p->sighand)) {

		if (!get_task_struct_rcu(p))

			return -ESRCH;

	if (!ret && sig && (sp = rcu_dereference(p->sighand))) {

		spin_lock_irqsave(&sp->siglock, flags);

		if (p->sighand != sp) {

			spin_unlock_irqrestore(&sp->siglock, flags);

			put_task_struct(p);

			goto retry;

		}

		if ((atomic_read(&sp->count) == 0) ||

				(atomic_read(&p->usage) == 0)) {

			spin_unlock_irqrestore(&sp->siglock, flags);

			return -ESRCH;

		}

		ret = __group_send_sig_info(sig, info, p);

		spin_unlock_irqrestore(&sp->siglock, flags);

		put_task_struct(p);

	}



	return ret;