[PATCH] posix-timers: remove false BUG_ON() from run_posix_cpu_timers() (3de463c7) · Commits · 戴 / test

do_exit() clears ->it_##clock##_expires, but nothing prevents another cpu to attach the timer to exiting process after that. After exit_notify() does 'write_unlock_irq(&tasklist_lock)' and before do_exit() calls 'schedule() local timer interrupt can find tsk->exit_state != 0. If that state was EXIT_DEAD (or another cpu does sys_wait4) interrupted task has ->signal == NULL. At this moment exiting task has no pending cpu timers, they were cleaned up in __exit_signal()->posix_cpu_timers_exit{,_group}(), so we can just return from irq. Signed-off-by:

Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

kernel/exit.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -825,14 +825,6 @@ fastcall NORET_TYPE void do_exit(long code)

		tsk->flags \|= PF_EXITING;

		/*
		* Make sure we don't try to process any timer firings
		* while we are already exiting.
		*/
		tsk->it_virt_expires = cputime_zero;
		tsk->it_prof_expires = cputime_zero;
		tsk->it_sched_expires = 0;

		if (unlikely(in_atomic()))
		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
		current->comm, current->pid,

kernel/posix-cpu-timers.c

+18 −18

Original line number	Diff line number	Diff line
		@@ -1285,12 +1285,11 @@ void run_posix_cpu_timers(struct task_struct *tsk)

		#undef UNEXPIRED

		BUG_ON(tsk->exit_state);

		/*
		* Double-check with locks held.
		*/
		read_lock(&tasklist_lock);
		if (likely(tsk->signal != NULL)) {
		spin_lock(&tsk->sighand->siglock);

		/*
		@@ -1309,6 +1308,7 @@ void run_posix_cpu_timers(struct task_struct *tsk)
		* spin until we've taken care of that timer below.
		*/
		spin_unlock(&tsk->sighand->siglock);
		}
		read_unlock(&tasklist_lock);

		/*

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