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Date: Mon, 17 Aug 2009 14:34:59 -0700
From: Suresh Siddha <suresh.b.siddha@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: "mingo@...e.hu" <mingo@...e.hu>, "hpa@...or.com" <hpa@...or.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
"Brown, Len" <len.brown@...el.com>
Subject: Re: [patch] clockevents_notify() need to be called with irq's
enabled
On Mon, 2009-08-17 at 14:27 -0700, Thomas Gleixner wrote:
> Suresh,
>
> On Mon, 17 Aug 2009, Suresh Siddha wrote:
>
> > --- tip.orig/arch/x86/kernel/process.c
> > +++ tip/arch/x86/kernel/process.c
> > @@ -508,17 +508,10 @@ 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.
> > - */
>
> Please keep the first sentence of the comment intact. Everything else
> looks fine.
Oops. Patch appended.
---
From: Suresh Siddha <suresh.b.siddha@...el.com>
Subject: take clockevents_lock with interrupts disabled
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 holding the clockevents_lock in clockevents_notify() with irq enabled
cpu B waiting for the clockevents_lock in clockevents_notify() with irq 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 stuck forever waiting for the spinlock and thus not reaching 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@...el.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
---
Index: tip/arch/x86/kernel/process.c
===================================================================
--- tip.orig/arch/x86/kernel/process.c
+++ tip/arch/x86/kernel/process.c
@@ -509,16 +509,12 @@ 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.
- */
- local_irq_enable();
+ * Force broadcast so ACPI can not interfere.
+ */
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);
Index: tip/drivers/acpi/processor_idle.c
===================================================================
--- tip.orig/drivers/acpi/processor_idle.c
+++ tip/drivers/acpi/processor_idle.c
@@ -162,8 +162,9 @@ static void lapic_timer_check_state(int
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(s
working++;
}
- lapic_timer_propagate_broadcast(pr);
+ smp_call_function_single(pr->id, lapic_timer_propagate_broadcast,
+ pr, 1);
return (working);
}
Index: tip/kernel/time/clockevents.c
===================================================================
--- tip.orig/kernel/time/clockevents.c
+++ tip/kernel/time/clockevents.c
@@ -137,11 +137,12 @@ int clockevents_program_event(struct clo
*/
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 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
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 re
default:
break;
}
- spin_unlock(&clockevents_lock);
+ spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_notify);
#endif
Index: tip/kernel/time/tick-broadcast.c
===================================================================
--- tip.orig/kernel/time/tick-broadcast.c
+++ tip/kernel/time/tick-broadcast.c
@@ -205,11 +205,11 @@ static void tick_handle_periodic_broadca
* 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
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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