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>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 0efa59e7e3af..66393d5c4c7c 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -162,8 +162,9 @@ static void lapic_timer_check_state(int state, struct acpi_processor *pr,
                 pr->power.timer_broadcast_on_state = state;
 }
 
-static void lapic_timer_propagate_broadcast(struct acpi_processor *pr)
+static void lapic_timer_propagate_broadcast(void *arg)
 {
+        struct acpi_processor *pr = (struct acpi_processor *) arg;
         unsigned long reason;
 
         reason = pr->power.timer_broadcast_on_state < INT_MAX ?
@@ -635,7 +636,8 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
                 working++;
         }
 
-        lapic_timer_propagate_broadcast(pr);
+        smp_call_function_single(pr->id, lapic_timer_propagate_broadcast,
+                                 pr, 1);
 
         return (working);
 }