Messages in this thread | | | Date | Tue, 29 Nov 2005 13:17:22 +0100 (CET) | From | Roman Zippel <> | Subject | Re: [PATCH 1/9] timer locking optimization |
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Hi,
On Tue, 29 Nov 2005, Oleg Nesterov wrote:
> > + base = timer->base; > > + spin_lock_irqsave(&base->lock, *flags); > > + while (unlikely(base != timer->base)) { > > + /* The timer has migrated to another CPU */ > > + spin_unlock(&base->lock); > > cpu_relax(); > > + base = timer->base; > > + spin_lock(&base->lock); > > This spins with interrupts disabled, not good, imho.
It's the slow path anyway, so restoring flags should indeed be fine.
> This way you can delete the timer (ret == 1), notice that timer's base > was changed after re-locking, goto restart, and get ret == 0.
ret is only set, but not reset, so if __mod_timer() deleted the timer it will return 1.
> Also, you have wrong value of 'base' after 'goto restart'.
Indeed, thanks for spotting this.
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