Messages in this thread | | | Date | Fri, 15 Apr 2011 13:15:06 +0900 | From | Tejun Heo <> | Subject | Re: [patch v3 3/3] percpu_counter: use atomic64 for counter in SMP |
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Hello,
On Thu, Apr 14, 2011 at 10:04:50AM +0800, shaohua.li@intel.com wrote: > Index: linux/lib/percpu_counter.c > =================================================================== > --- linux.orig/lib/percpu_counter.c 2011-04-14 09:53:04.000000000 +0800 > +++ linux/lib/percpu_counter.c 2011-04-14 10:01:29.000000000 +0800 > @@ -59,13 +59,17 @@ void percpu_counter_set(struct percpu_co > { > int cpu; > > - spin_lock(&fbc->lock); > + /* > + * Don't really need to disable preempt here, just make sure there is > + * no big latency because of preemption > + */ > + preempt_disable(); > for_each_possible_cpu(cpu) { > s32 *pcount = per_cpu_ptr(fbc->counters, cpu); > *pcount = 0; > } > - fbc->count = amount; > - spin_unlock(&fbc->lock); > + atomic64_set(&fbc->count, amount); > + preempt_enable();
Disabling preemption here doesn't make any sense. percpu_counter_set() inherently requires its users to guarantee that no other user is modifying the percpu counter.
Thanks.
-- tejun
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