I've missed the thread "avoiding bad sleeps" last week. I've had a similar problem and I would like to discuss the solution I've used to avoid it.
I want to wake up a sleeping process from an IRQ handler. In the process, if I use a interruptible_sleep_on(), I need first to restore flags (otherwise the process will sleep forever).
restore_flags(flags);
// <<== here IRQ handler possibly call wake_up()
interruptible_sleep_on(&my_queue);
If I first enable interrupts and then call sleep_on, sometimes (often) the wake_up is called (due to a pending interrupt) when the wait_queue is empty.
I've written a modified version of interruptible_sleep_on which takes an additionnal argument : flags to be restored.
my_interruptible_sleep_on(&my_queue, flags);
It seems to be ok. I've no more bad sleeps or more exactly rarely and that why I submit this to you. Is my way to do it correct ?
I've joined at the end of this mail the modified function.
Thanks,
Christophe Barb�
long my_interruptible_sleep_on_timeout(struct wait_queue **p, long timeout, unsigned long oflags)
{
unsigned long flags;
struct wait_queue wait;
current->state = TASK_INTERRUPTIBLE;
// SLEEP_ON_HEAD
wait.task = current;
write_lock_irq(&waitqueue_lock);
__add_wait_queue(p, &wait);
write_unlock(&waitqueue_lock);
restore_flags(oflags);
timeout = schedule_timeout(timeout);
// SLEEP_ON_TAIL
write_lock_irqsave(&waitqueue_lock,flags);
__remove_wait_queue(p, &wait);
write_unlock_irqrestore(&waitqueue_lock,flags);
return timeout;
}
-- Christophe Barb� Software Engineer Lineo High Availability Group 42-46, rue M�d�ric 92110 Clichy - France phone (33).1.41.40.02.12 fax (33).1.41.40.02.01 www.lineo.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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