path: root/kernel/time
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authorThomas Gleixner <tglx@linutronix.de>2013-05-28 09:33:01 +0200
committerThomas Gleixner <tglx@linutronix.de>2013-05-28 09:33:01 +0200
commit2938d2757fc99c26aa678ce4eba910c4a77c3a55 (patch)
tree67a083021705f6cac75f6bea2fa83e975807c624 /kernel/time
parente4aa937ec75df0eea0bee03bffa3303ad36c986b (diff)
tick: Cure broadcast false positive pending bit warning
commit 26517f3e (tick: Avoid programming the local cpu timer if broadcast pending) added a warning if the cpu enters broadcast mode again while the pending bit is still set. Meelis reported that the warning triggers. There are two corner cases which have been not considered: 1) cpuidle calls clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER) twice. That can result in the following scenario CPU0 CPU1 cpuidle_idle_call() clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER) set cpu in tick_broadcast_oneshot_mask broadcast interrupt event expired for cpu1 set pending bit acpi_idle_enter_simple() clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER) WARN_ON(pending bit) Move the WARN_ON into the section where we enter broadcast mode so it wont provide false positives on the second call. 2) safe_halt() enables interrupts, so a broadcast interrupt can be delivered befor the broadcast mode is disabled. That sets the pending bit for the CPU which receives the broadcast interrupt. Though the interrupt is delivered right away from the broadcast handler and leaves the pending bit stale. Clear the pending bit for the current cpu in the broadcast handler. Reported-and-tested-by: Meelis Roos <mroos@linux.ee> Cc: Len Brown <lenb@kernel.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Rafael J. Wysocki <rjw@sisk.pl> Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1305271841130.4220@ionos Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time')
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 24938d57766..0c739423b0f 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -511,6 +511,12 @@ again:
+ /*
+ * Remove the current cpu from the pending mask. The event is
+ * delivered immediately in tick_do_broadcast() !
+ */
+ cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
/* Take care of enforced broadcast requests */
cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
@@ -575,8 +581,8 @@ void tick_broadcast_oneshot_control(unsigned long reason)
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
- WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
+ WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
* We only reprogram the broadcast timer if we