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authorThomas Gleixner <tglx@linutronix.de>2013-07-01 22:14:10 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-07-25 14:07:29 -0700
commit1c0d08e652c18e3f3198969435fef31941b2eec3 (patch)
tree47f205d38ddcc6a2a9e6d2f0b1cd41bfbf87b448 /kernel/time
parent2dc04d3333049098691eb652e06d52fbd80771d2 (diff)
downloadlinaro-lsk-1c0d08e652c18e3f3198969435fef31941b2eec3.tar.gz
tick: Sanitize broadcast control logic
commit 07bd1172902e782f288e4d44b1fde7dec0f08b6f upstream. The recent implementation of a generic dummy timer resulted in a different registration order of per cpu local timers which made the broadcast control logic go belly up. If the dummy timer is the first clock event device which is registered for a CPU, then it is installed, the broadcast timer is initialized and the CPU is marked as broadcast target. If a real clock event device is installed after that, we can fail to take the CPU out of the broadcast mask. In the worst case we end up with two periodic timer events firing for the same CPU. One from the per cpu hardware device and one from the broadcast. Now the problem is that we have no way to distinguish whether the system is in a state which makes broadcasting necessary or the broadcast bit was set due to the nonfunctional dummy timer installment. To solve this we need to keep track of the system state seperately and provide a more detailed decision logic whether we keep the CPU in broadcast mode or not. The old decision logic only clears the broadcast mode, if the newly installed clock event device is not affected by power states. The new logic clears the broadcast mode if one of the following is true: - The new device is not affected by power states. - The system is not in a power state affected mode - The system has switched to oneshot mode. The oneshot broadcast is controlled from the deep idle state. The CPU is not in idle at this point, so it's safe to remove it from the mask. If we clear the broadcast bit for the CPU when a new device is installed, we also shutdown the broadcast device when this was the last CPU in the broadcast mask. If the broadcast bit is kept, then we leave the new device in shutdown state and rely on the broadcast to deliver the timer interrupts via the broadcast ipis. Reported-and-tested-by: Stehle Vincent-B46079 <B46079@freescale.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Cc: John Stultz <john.stultz@linaro.org>, Cc: Mark Rutland <mark.rutland@arm.com> Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1307012153060.4013@ionos.tec.linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-broadcast.c70
-rw-r--r--kernel/time/tick-common.c3
2 files changed, 61 insertions, 12 deletions
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 20d6fba7065..c389f068aca 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -29,6 +29,7 @@
static struct tick_device tick_broadcast_device;
static cpumask_var_t tick_broadcast_mask;
+static cpumask_var_t tick_broadcast_on;
static cpumask_var_t tmpmask;
static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
static int tick_broadcast_force;
@@ -123,8 +124,9 @@ static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
*/
int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
{
+ struct clock_event_device *bc = tick_broadcast_device.evtdev;
unsigned long flags;
- int ret = 0;
+ int ret;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
@@ -138,20 +140,59 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
dev->event_handler = tick_handle_periodic;
tick_device_setup_broadcast_func(dev);
cpumask_set_cpu(cpu, tick_broadcast_mask);
- tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
+ tick_broadcast_start_periodic(bc);
ret = 1;
} else {
/*
- * When the new device is not affected by the stop
- * feature and the cpu is marked in the broadcast mask
- * then clear the broadcast bit.
+ * Clear the broadcast bit for this cpu if the
+ * device is not power state affected.
*/
- if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
- int cpu = smp_processor_id();
+ if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
cpumask_clear_cpu(cpu, tick_broadcast_mask);
- tick_broadcast_clear_oneshot(cpu);
- } else {
+ else
tick_device_setup_broadcast_func(dev);
+
+ /*
+ * Clear the broadcast bit if the CPU is not in
+ * periodic broadcast on state.
+ */
+ if (!cpumask_test_cpu(cpu, tick_broadcast_on))
+ cpumask_clear_cpu(cpu, tick_broadcast_mask);
+
+ switch (tick_broadcast_device.mode) {
+ case TICKDEV_MODE_ONESHOT:
+ /*
+ * If the system is in oneshot mode we can
+ * unconditionally clear the oneshot mask bit,
+ * because the CPU is running and therefore
+ * not in an idle state which causes the power
+ * state affected device to stop. Let the
+ * caller initialize the device.
+ */
+ tick_broadcast_clear_oneshot(cpu);
+ ret = 0;
+ break;
+
+ case TICKDEV_MODE_PERIODIC:
+ /*
+ * If the system is in periodic mode, check
+ * whether the broadcast device can be
+ * switched off now.
+ */
+ if (cpumask_empty(tick_broadcast_mask) && bc)
+ clockevents_shutdown(bc);
+ /*
+ * If we kept the cpu in the broadcast mask,
+ * tell the caller to leave the per cpu device
+ * in shutdown state. The periodic interrupt
+ * is delivered by the broadcast device.
+ */
+ ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
+ break;
+ default:
+ /* Nothing to do */
+ ret = 0;
+ break;
}
}
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
@@ -281,6 +322,7 @@ static void tick_do_broadcast_on_off(unsigned long *reason)
switch (*reason) {
case CLOCK_EVT_NOTIFY_BROADCAST_ON:
case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
+ cpumask_set_cpu(cpu, tick_broadcast_on);
if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
if (tick_broadcast_device.mode ==
TICKDEV_MODE_PERIODIC)
@@ -290,8 +332,12 @@ static void tick_do_broadcast_on_off(unsigned long *reason)
tick_broadcast_force = 1;
break;
case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
- if (!tick_broadcast_force &&
- cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
+ if (tick_broadcast_force)
+ break;
+ cpumask_clear_cpu(cpu, tick_broadcast_on);
+ if (!tick_device_is_functional(dev))
+ break;
+ if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
if (tick_broadcast_device.mode ==
TICKDEV_MODE_PERIODIC)
tick_setup_periodic(dev, 0);
@@ -349,6 +395,7 @@ void tick_shutdown_broadcast(unsigned int *cpup)
bc = tick_broadcast_device.evtdev;
cpumask_clear_cpu(cpu, tick_broadcast_mask);
+ cpumask_clear_cpu(cpu, tick_broadcast_on);
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
if (bc && cpumask_empty(tick_broadcast_mask))
@@ -792,6 +839,7 @@ bool tick_broadcast_oneshot_available(void)
void __init tick_broadcast_init(void)
{
zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
+ zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
#ifdef CONFIG_TICK_ONESHOT
zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 5d3fb100bc0..7ce5e5a4a4c 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -194,7 +194,8 @@ static void tick_setup_device(struct tick_device *td,
* When global broadcasting is active, check if the current
* device is registered as a placeholder for broadcast mode.
* This allows us to handle this x86 misfeature in a generic
- * way.
+ * way. This function also returns !=0 when we keep the
+ * current active broadcast state for this CPU.
*/
if (tick_device_uses_broadcast(newdev, cpu))
return;