From f833bab87fca5c3ce13778421b1365845843b976 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Mon, 17 Aug 2009 14:34:59 -0700 Subject: 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 Signed-off-by: Venkatesh Pallipadi Cc: "Pallipadi Venkatesh" Cc: "Brown Len" LKML-Reference: <1250544899.2709.210.camel@sbs-t61.sc.intel.com> Signed-off-by: Thomas Gleixner --- kernel/time/clockevents.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) (limited to 'kernel/time/clockevents.c') diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c index a6dcd67b041d..620b58abdc32 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 -- cgit v1.2.3