Re: [PATCH] improve spinlock debugging
george anzinger (george@mvista.com)
Tue, 04 Dec 2001 13:25:40 -0800
Robert Love wrote:
>
> On Tue, 2001-12-04 at 15:30, george anzinger wrote:
>
> > spin_lockirq
> >
> > spin_unlock
> >
> > restore_irq
>
> Given this order, couldn't we _always_ not touch the preempt count since
> irq's are off?
>
> Further, since I doubt we ever see:
>
> spin_lock_irq
> restore_irq
> spin_unlock
>
> and the common use is:
>
> spin_lock_irq
> spin_unlock_irq
>
> Isn't it safe to have spin_lock_irq *never* touch the preempt count?
>
NO. The problem is the first example above. The spin_unlock will down
count, but the spin_lockirq did NOT do the paired up count (been there,
done that). This is where we need the spin_unlock_no_irq_restore.
--
George george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Real time sched: http://sourceforge.net/projects/rtsched/
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