Re: workqueue code needing preemption disabled

From: Steven Rostedt
Date: Mon Mar 18 2013 - 12:27:10 EST

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:

-> preempt_schedule();


Again, with -rt, spin_lock_irq() does not prevent interrupts nor

-- Steve

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