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authorSuresh Siddha <suresh.b.siddha@intel.com>2009-08-17 14:34:59 -0700
committerThomas Gleixner <tglx@linutronix.de>2009-08-19 18:15:10 +0200
commitf833bab87fca5c3ce13778421b1365845843b976 (patch)
tree020c3e6a70dba34544c963c34647b605035be8fb /kernel/time/clockevents.c
parentde809347aeef0a68c04576c464414d0e4dce59fc (diff)
clockevent: Prevent dead lock on clockevents_lock
Currently clockevents_notify() is called with interrupts enabled at some places and interrupts disabled at some other places. This results in a deadlock in this scenario. cpu A holds clockevents_lock in clockevents_notify() with irqs enabled cpu B waits for clockevents_lock in clockevents_notify() with irqs disabled cpu C doing set_mtrr() which will try to rendezvous of all the cpus. This will result in C and A come to the rendezvous point and waiting for B. B is stuck forever waiting for the spinlock and thus not reaching the rendezvous point. Fix the clockevents code so that clockevents_lock is taken with interrupts disabled and thus avoid the above deadlock. Also call lapic_timer_propagate_broadcast() on the destination cpu so that we avoid calling smp_call_function() in the clockevents notifier chain. This issue left us wondering if we need to change the MTRR rendezvous logic to use stop machine logic (instead of smp_call_function) or add a check in spinlock debug code to see if there are other spinlocks which gets taken under both interrupts enabled/disabled conditions. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Cc: "Pallipadi Venkatesh" <venkatesh.pallipadi@intel.com> Cc: "Brown Len" <len.brown@intel.com> LKML-Reference: <1250544899.2709.210.camel@sbs-t61.sc.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/clockevents.c')
-rw-r--r--kernel/time/clockevents.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index a6dcd67b041..620b58abdc3 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -137,11 +137,12 @@ int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
*/
int clockevents_register_notifier(struct notifier_block *nb)
{
+ unsigned long flags;
int ret;
- spin_lock(&clockevents_lock);
+ spin_lock_irqsave(&clockevents_lock, flags);
ret = raw_notifier_chain_register(&clockevents_chain, nb);
- spin_unlock(&clockevents_lock);
+ spin_unlock_irqrestore(&clockevents_lock, flags);
return ret;
}
@@ -178,16 +179,18 @@ static void clockevents_notify_released(void)
*/
void clockevents_register_device(struct clock_event_device *dev)
{
+ unsigned long flags;
+
BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
BUG_ON(!dev->cpumask);
- spin_lock(&clockevents_lock);
+ spin_lock_irqsave(&clockevents_lock, flags);
list_add(&dev->list, &clockevent_devices);
clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
clockevents_notify_released();
- spin_unlock(&clockevents_lock);
+ spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_register_device);
@@ -235,8 +238,9 @@ void clockevents_exchange_device(struct clock_event_device *old,
void clockevents_notify(unsigned long reason, void *arg)
{
struct list_head *node, *tmp;
+ unsigned long flags;
- spin_lock(&clockevents_lock);
+ spin_lock_irqsave(&clockevents_lock, flags);
clockevents_do_notify(reason, arg);
switch (reason) {
@@ -251,7 +255,7 @@ void clockevents_notify(unsigned long reason, void *arg)
default:
break;
}
- spin_unlock(&clockevents_lock);
+ spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_notify);
#endif