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Subject[tip:timers/urgent] clockevent: Prevent dead lock on clockevents_lock
Commit-ID:  f833bab87fca5c3ce13778421b1365845843b976
Gitweb: http://git.kernel.org/tip/f833bab87fca5c3ce13778421b1365845843b976
Author: Suresh Siddha <suresh.b.siddha@intel.com>
AuthorDate: Mon, 17 Aug 2009 14:34:59 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 19 Aug 2009 18:15:10 +0200

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>


---
arch/x86/kernel/process.c | 6 +-----
drivers/acpi/processor_idle.c | 6 ++++--
kernel/time/clockevents.c | 16 ++++++++++------
kernel/time/tick-broadcast.c | 7 +++----
4 files changed, 18 insertions(+), 17 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 994dd6a..071166a 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);

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 0efa59e..66393d5 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);
}
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index a6dcd67..620b58a 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
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 877dbed..c2ec250 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -205,11 +205,11 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
* Powerstate information: The system enters/leaves a state, where
* affected devices might stop
*/
-static void tick_do_broadcast_on_off(void *why)
+static void tick_do_broadcast_on_off(unsigned long *reason)
{
struct clock_event_device *bc, *dev;
struct tick_device *td;
- unsigned long flags, *reason = why;
+ unsigned long flags;
int cpu, bc_stopped;

spin_lock_irqsave(&tick_broadcast_lock, flags);
@@ -276,8 +276,7 @@ void tick_broadcast_on_off(unsigned long reason, int *oncpu)
printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
"offline CPU #%d\n", *oncpu);
else
- smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
- &reason, 1);
+ tick_do_broadcast_on_off(&reason);
}

/*

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