Messages in this thread | | | Subject | Re: workqueue code needing preemption disabled | From | Steven Rostedt <> | Date | Mon, 18 Mar 2013 12:27:00 -0400 |
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On Mon, 2013-03-18 at 12:23 -0400, Steven Rostedt wrote:
> > Maybe I'm confused but I can't really see how the above would be a > > problem to workqueue in itself. Both rq->lock and gcwq->lock are > > irq-safe, so spin_lock() not disabling preemption shouldn't be a > > problem. Are CPU hotplug operations involved? > > No CPU hotplug is involved here. But I will note that gcwq->lock in -rt > is not irq -safe. That is, in rt the spin_lock_irq(&gcwq->lock) really > becomes a special "mutex_lock(&gcwq->lock)".
IOW, what can happen in -rt here is:
spin_lock_irq(&gcwq->lock); [...] <interrupt> -> preempt_schedule(); schedule(); try_to_wake_up_local();
[...] spin_unlock_irq(&gcwq->lock);
Again, with -rt, spin_lock_irq() does not prevent interrupts nor preemption.
-- Steve
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