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Commit 4aa73611 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Thomas Gleixner
Browse files

posix-timers: don't switch to ->group_leader if ->it_process dies 



posix_timer_event() drops SIGEV_THREAD_ID and switches to ->group_leader
if send_sigqueue() fails.

This is not very useful and doesn't work reliably.  send_sigqueue() can
only fail if ->it_process is dead.  But it can die before it dequeues the
SI_TIMER signal, in that case the timer stops anyway.

Remove this code.  I guess it was needed a long ago to ensure that the
timer is not destroyed when when its creator thread dies.

Q: perhaps it makes sense to change sys_timer_settime() to return an error
if ->it_process is dead?

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent bb34d92f

kernel/posix-timers.c

+5 −14
Original line number Diff line number Diff line
@@ -298,6 +298,7 @@ void do_schedule_next_timer(struct siginfo *info) 


int posix_timer_event(struct k_itimer *timr, int si_private)

{

	int shared, ret;

	/*

	 * FIXME: if ->sigq is queued we can race with

	 * dequeue_signal()->do_schedule_next_timer().
@@ -316,20 +317,10 @@ int posix_timer_event(struct k_itimer *timr, int si_private) 
	timr->sigq->info.si_tid = timr->it_id;

	timr->sigq->info.si_value = timr->it_sigev_value;



	if (timr->it_sigev_notify & SIGEV_THREAD_ID) {

		struct task_struct *leader;

		int ret = send_sigqueue(timr->sigq, timr->it_process, 0);



		if (likely(ret >= 0))

			return ret;



		timr->it_sigev_notify = SIGEV_SIGNAL;

		leader = timr->it_process->group_leader;

		put_task_struct(timr->it_process);

		timr->it_process = leader;

	}



	return send_sigqueue(timr->sigq, timr->it_process, 1);

	shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);

	ret = send_sigqueue(timr->sigq, timr->it_process, shared);

	/* If we failed to send the signal the timer stops. */

	return ret > 0;

}

EXPORT_SYMBOL_GPL(posix_timer_event);