Commit bb6eddf7 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarXiaotian Feng <dfeng@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarXiaotian Feng <dfeng@redhat.com>
Cc: stable@kernel.org
parent e9c0748b

kernel/time/clockevents.c

+15 −3
Original line number Original line Diff line number Diff line
@@ -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;

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