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Subject[PATCH 08/97] clockevents: Prevent clockevent_devices list corruption on cpu hotplug
Date
From: Thomas Gleixner <tglx@linutronix.de>

commit bb6eddf7676e1c1f3e637aa93c5224488d99036f upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
kernel/time/clockevents.c | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 620b58a..9484be4 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -237,8 +237,9 @@ void clockevents_exchange_device(struct clock_event_device *old,
*/
void clockevents_notify(unsigned long reason, void *arg)
{
- struct list_head *node, *tmp;
+ struct clock_event_device *dev, *tmp;
unsigned long flags;
+ int cpu;

spin_lock_irqsave(&clockevents_lock, flags);
clockevents_do_notify(reason, arg);
@@ -249,8 +250,19 @@ void clockevents_notify(unsigned long reason, void *arg)
* Unregister the clock event devices which were
* released from the users in the notify chain.
*/
- list_for_each_safe(node, tmp, &clockevents_released)
- list_del(node);
+ list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
+ 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;
default:
break;
--
1.6.6


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