d2b20b1154
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>
145 lines
3.1 KiB
C
145 lines
3.1 KiB
C
/*
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* Fast batching percpu counters.
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*/
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#include <linux/percpu_counter.h>
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#include <linux/notifier.h>
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#include <linux/mutex.h>
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#include <linux/init.h>
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#include <linux/cpu.h>
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#include <linux/module.h>
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#ifdef CONFIG_HOTPLUG_CPU
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static LIST_HEAD(percpu_counters);
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static DEFINE_MUTEX(percpu_counters_lock);
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#endif
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void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
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{
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int cpu;
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spin_lock(&fbc->lock);
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for_each_possible_cpu(cpu) {
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s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
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*pcount = 0;
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}
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fbc->count = amount;
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spin_unlock(&fbc->lock);
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}
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EXPORT_SYMBOL(percpu_counter_set);
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void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
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{
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s64 count;
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s32 *pcount;
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int cpu = get_cpu();
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pcount = per_cpu_ptr(fbc->counters, cpu);
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count = *pcount + amount;
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if (count >= batch || count <= -batch) {
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spin_lock(&fbc->lock);
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fbc->count += count;
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*pcount = 0;
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spin_unlock(&fbc->lock);
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} else {
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*pcount = count;
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}
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put_cpu();
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}
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EXPORT_SYMBOL(__percpu_counter_add);
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/*
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* Add up all the per-cpu counts, return the result. This is a more accurate
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* but much slower version of percpu_counter_read_positive()
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*/
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s64 __percpu_counter_sum(struct percpu_counter *fbc)
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{
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s64 ret;
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int cpu;
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spin_lock(&fbc->lock);
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ret = fbc->count;
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for_each_online_cpu(cpu) {
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s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
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ret += *pcount;
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}
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spin_unlock(&fbc->lock);
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return ret;
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}
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EXPORT_SYMBOL(__percpu_counter_sum);
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static struct lock_class_key percpu_counter_irqsafe;
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int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
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{
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spin_lock_init(&fbc->lock);
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fbc->count = amount;
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fbc->counters = alloc_percpu(s32);
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if (!fbc->counters)
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return -ENOMEM;
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#ifdef CONFIG_HOTPLUG_CPU
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mutex_lock(&percpu_counters_lock);
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list_add(&fbc->list, &percpu_counters);
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mutex_unlock(&percpu_counters_lock);
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#endif
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return 0;
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}
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EXPORT_SYMBOL(percpu_counter_init);
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int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount)
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{
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int err;
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err = percpu_counter_init(fbc, amount);
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if (!err)
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lockdep_set_class(&fbc->lock, &percpu_counter_irqsafe);
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return err;
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}
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void percpu_counter_destroy(struct percpu_counter *fbc)
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{
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if (!fbc->counters)
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return;
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free_percpu(fbc->counters);
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#ifdef CONFIG_HOTPLUG_CPU
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mutex_lock(&percpu_counters_lock);
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list_del(&fbc->list);
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mutex_unlock(&percpu_counters_lock);
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#endif
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}
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EXPORT_SYMBOL(percpu_counter_destroy);
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#ifdef CONFIG_HOTPLUG_CPU
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static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
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unsigned long action, void *hcpu)
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{
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unsigned int cpu;
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struct percpu_counter *fbc;
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if (action != CPU_DEAD)
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return NOTIFY_OK;
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cpu = (unsigned long)hcpu;
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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_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_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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}
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static int __init percpu_counter_startup(void)
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{
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hotcpu_notifier(percpu_counter_hotcpu_callback, 0);
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return 0;
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}
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module_init(percpu_counter_startup);
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#endif
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