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authorThomas Gleixner <tglx@linutronix.de>2012-04-18 17:31:58 +0200
committerThomas Gleixner <tglx@linutronix.de>2012-04-19 21:27:35 +0200
commitb9a6a23566960d0dd3f51e2e68b472cd61911078 (patch)
treed9da5fb202a21b9036e961a5f4d3190e57343a6c /kernel
parentb435092f70ec5ebbfb6d075d5bf3c631b49a51de (diff)
downloadlinux-b9a6a23566960d0dd3f51e2e68b472cd61911078.tar.gz
tick: Ensure that the broadcast device is initialized
Santosh found another trap when we avoid to initialize the broadcast device in the switch_to_oneshot code. The broadcast device might be still in SHUTDOWN state when we actually need to use it. That obviously breaks, as set_next_event() is called on a shutdown device. This did not break on x86, but Suresh analyzed it: From the review, most likely on Sven's system we are force enabling the hpet using the pci quirk's method very late. And in this case, hpet_clockevent (which will be global_clock_event) handler can be null, specifically as this platform might not be using deeper c-states and using the reliable APIC timer. Prior to commit 'fa4da365bc7772c', that handler will be set to 'tick_handle_oneshot_broadcast' when we switch the broadcast timer to oneshot mode, even though we don't use it. Post commit 'fa4da365bc7772c', we stopped switching the broadcast mode to oneshot as this is not really needed and his platform's global_clock_event's handler will remain null. While on my SNB laptop, same is set to 'clockevents_handle_noop' because hpet gets enabled very early. (noop handler on my platform set when the early enabled hpet timer gets replaced by the lapic timer). But the commit 'fa4da365bc7772c' tracked the broadcast timer mode in the SW as oneshot, even though it didn't touch the HW timer. During resume however, tick_resume_broadcast() saw the SW broadcast mode as oneshot and actually programmed the broadcast device also into oneshot mode. So this triggered the null pointer de-reference after the hpet wraps around and depending on what the hpet counter is set to. On the normal platforms where hpet gets enabled early we should be seeing a spurious interrupt (in my SNB laptop I see one spurious interrupt after around 5 minutes ;) which is 32-bit hpet counter wraparound time), but that's a separate issue. Enforce the mode setting when trying to set an event. Reported-and-tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: torvalds@linux-foundation.org Cc: svenjoac@gmx.de Cc: rjw@sisk.pl Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1204181723350.2542@ionos
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/tick-broadcast.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 119aca5c684..029531f3818 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -373,6 +373,9 @@ static int tick_broadcast_set_event(ktime_t expires, int force)
{
struct clock_event_device *bc = tick_broadcast_device.evtdev;
+ if (bc->mode != CLOCK_EVT_MODE_ONESHOT)
+ clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
+
return clockevents_program_event(bc, expires, force);
}