posix-timers: don't switch to ->group_leader if ->it_process dies (4aa73611) · Commits · 戴 / test

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:

Oleg Nesterov <oleg@tv-sign.ru> Cc: mingo@elte.hu Cc: Roland McGrath <roland@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de>

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);

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