diff options
author | Stuart Hayes <stuart.w.hayes@gmail.com> | 2014-04-29 18:55:02 -0400 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2014-04-30 06:34:51 -0400 |
commit | 6c6c0d5a1c949d2e084706f9e5fb1fccc175b265 (patch) | |
tree | 997d02e96adcbae3d211c107c567965630b6aa54 /kernel | |
parent | fb0095da19a2e905dfa3141a7704d9614f64992c (diff) |
hrtimer: Prevent all reprogramming if hang detected
If the last hrtimer interrupt detected a hang it sets hang_detected=1
and programs the clock event device with a delay to let the system
make progress.
If hang_detected == 1, we prevent reprogramming of the clock event
device in hrtimer_reprogram() but not in hrtimer_force_reprogram().
This can lead to the following situation:
hrtimer_interrupt()
hang_detected = 1;
program ce device to Xms from now (hang delay)
We have two timers pending:
T1 expires 50ms from now
T2 expires 5s from now
Now T1 gets canceled, which causes hrtimer_force_reprogram() to be
invoked, which in turn programs the clock event device to T2 (5
seconds from now).
Any hrtimer_start after that will not reprogram the hardware due to
hang_detected still being set. So we effectivly block all timers until
the T2 event fires and cleans up the hang situation.
Add a check for hang_detected to hrtimer_force_reprogram() which
prevents the reprogramming of the hang delay in the hardware
timer. The subsequent hrtimer_interrupt will resolve all outstanding
issues.
[ tglx: Rewrote subject and changelog and fixed up the comment in
hrtimer_force_reprogram() ]
Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Link: http://lkml.kernel.org/r/53602DC6.2060101@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/hrtimer.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index d55092ceee29..e3724fdac2da 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c | |||
@@ -569,6 +569,23 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal) | |||
569 | 569 | ||
570 | cpu_base->expires_next.tv64 = expires_next.tv64; | 570 | cpu_base->expires_next.tv64 = expires_next.tv64; |
571 | 571 | ||
572 | /* | ||
573 | * If a hang was detected in the last timer interrupt then we | ||
574 | * leave the hang delay active in the hardware. We want the | ||
575 | * system to make progress. That also prevents the following | ||
576 | * scenario: | ||
577 | * T1 expires 50ms from now | ||
578 | * T2 expires 5s from now | ||
579 | * | ||
580 | * T1 is removed, so this code is called and would reprogram | ||
581 | * the hardware to 5s from now. Any hrtimer_start after that | ||
582 | * will not reprogram the hardware due to hang_detected being | ||
583 | * set. So we'd effectivly block all timers until the T2 event | ||
584 | * fires. | ||
585 | */ | ||
586 | if (cpu_base->hang_detected) | ||
587 | return; | ||
588 | |||
572 | if (cpu_base->expires_next.tv64 != KTIME_MAX) | 589 | if (cpu_base->expires_next.tv64 != KTIME_MAX) |
573 | tick_program_event(cpu_base->expires_next, 1); | 590 | tick_program_event(cpu_base->expires_next, 1); |
574 | } | 591 | } |