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 --- arch/x86/kernel/process.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'arch/x86/kernel/process.c') diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 994dd6a4a2a..071166a4ba8 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -519,16 +519,12 @@ static void c1e_idle(void) if (!cpumask_test_cpu(cpu, c1e_mask)) { cpumask_set_cpu(cpu, c1e_mask); /* - * Force broadcast so ACPI can not interfere. Needs - * to run with interrupts enabled as it uses - * smp_function_call. + * Force broadcast so ACPI can not interfere. */ - local_irq_enable(); clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_FORCE, &cpu); printk(KERN_INFO "Switch to broadcast mode on CPU%d\n", cpu); - local_irq_disable(); } clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu); -- cgit v1.2.3