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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
This commit is contained in:
Thomas Gleixner 2009-12-10 15:35:10 +01:00
parent e9c0748b68
commit bb6eddf767
1 changed files with 15 additions and 3 deletions
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18
kernel/time/clockevents.c
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@ -238,8 +238,9 @@ void clockevents_exchange_device(struct clock_event_device *old,
*/ */
void clockevents_notify(unsigned long reason, void *arg) void clockevents_notify(unsigned long reason, void *arg)
{ {
struct list_head *node, *tmp; struct clock_event_device *dev, *tmp;
unsigned long flags; unsigned long flags;
int cpu;
spin_lock_irqsave(&clockevents_lock, flags); spin_lock_irqsave(&clockevents_lock, flags);
clockevents_do_notify(reason, arg); clockevents_do_notify(reason, arg);
@ -250,8 +251,19 @@ void clockevents_notify(unsigned long reason, void *arg)
* Unregister the clock event devices which were * Unregister the clock event devices which were
* released from the users in the notify chain. * released from the users in the notify chain.
*/ */
list_for_each_safe(node, tmp, &clockevents_released) list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
list_del(node); list_del(&dev->list);
/*
* Now check whether the CPU has left unused per cpu devices
*/
cpu = *((int *)arg);
list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
if (cpumask_test_cpu(cpu, dev->cpumask) &&
cpumask_weight(dev->cpumask) == 1) {
BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
list_del(&dev->list);
}
}
break; break;
default: default:
break; break;