clockevents: Prevent clockevent_devices list corruption on cpu hotplug
Xiaotian Feng triggered a list corruption in the clock events list on CPU hotplug and debugged the root cause. If a CPU registers more than one per cpu clock event device, then only the active clock event device is removed on CPU_DEAD. The unused devices are kept in the clock events device list. On CPU up the clock event devices are registered again, which means that we list_add an already enqueued list_head. That results in list corruption. Resolve this by removing all devices which are associated to the dead CPU on CPU_DEAD. Reported-by: Xiaotian Feng <dfeng@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Xiaotian Feng <dfeng@redhat.com> Cc: stable@kernel.org
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@ -238,8 +238,9 @@ void clockevents_exchange_device(struct clock_event_device *old,
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*/
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void clockevents_notify(unsigned long reason, void *arg)
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{
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struct list_head *node, *tmp;
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struct clock_event_device *dev, *tmp;
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unsigned long flags;
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int cpu;
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spin_lock_irqsave(&clockevents_lock, flags);
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clockevents_do_notify(reason, arg);
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@ -250,8 +251,19 @@ void clockevents_notify(unsigned long reason, void *arg)
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* Unregister the clock event devices which were
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* released from the users in the notify chain.
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*/
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list_for_each_safe(node, tmp, &clockevents_released)
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list_del(node);
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list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
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list_del(&dev->list);
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/*
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* Now check whether the CPU has left unused per cpu devices
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*/
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cpu = *((int *)arg);
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list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
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if (cpumask_test_cpu(cpu, dev->cpumask) &&
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cpumask_weight(dev->cpumask) == 1) {
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BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
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list_del(&dev->list);
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}
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}
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break;
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default:
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break;
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