Re: [patch 2/2] hrtimer

[Oleg Nesterov]

I also think this is racy.

CPU_0					CPU_1

hrtimer_wakeup:

	task = t->task;
	t->task = NULL;

	<--- INTERRUPT --->

					task is woken by signal,
					do_nanosleep() sees t->task == NULL,
					returns without hrtimer_cancel(),
					and __exits__.

	<--- RESUME --->

	wake_up_process(task);

Instead of exit(), 'task' can go to TASK_STOPPED or TASK_UNINTERRUPTIBLE
after return from do_nanosleep(), it will be awakened by hrtimer_wakeup()
unexpectedly.

Oleg.

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