Re: [PATCH] improve spinlock debugging

[george anzinger <george@mvista.com>]

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/