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Add irq protection in the percpu-counters cpu-hotplug-callback path
Some of the per-cpu counters and thus their locks are accessed from IRQ contexts. This can cause a deadlock if it interrupts a cpu-offline thread which is transferring a dead-cpu's counts to the global counter. Add appropriate IRQ protection in the cpu-hotplug callback path. Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -124,12 +124,13 @@ static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
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mutex_lock(&percpu_counters_lock);
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list_for_each_entry(fbc, &percpu_counters, list) {
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s32 *pcount;
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unsigned long flags;
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spin_lock(&fbc->lock);
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spin_lock_irqsave(&fbc->lock, flags);
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pcount = per_cpu_ptr(fbc->counters, cpu);
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fbc->count += *pcount;
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*pcount = 0;
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spin_unlock(&fbc->lock);
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spin_unlock_irqrestore(&fbc->lock, flags);
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}
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mutex_unlock(&percpu_counters_lock);
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return NOTIFY_OK;
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