diff options
| author | Anton Blanchard <anton@samba.org> | 2014-05-09 17:47:12 +1000 |
|---|---|---|
| committer | Show Liu <show.liu@linaro.org> | 2014-06-18 12:05:12 +0800 |
| commit | 6b7044020d321b7e501553a73227933a70901477 (patch) | |
| tree | a8cfda577ff64119ab1347ff8f962424f74ec331 /arch | |
| parent | fc86d4bdf343f414bef2a9d1a6996b797bddd944 (diff) | |
powerpc: irq work racing with timer interrupt can result in timer interrupt hang
commit 8050936caf125fbe54111ba5e696b68a360556ba upstream.
I am seeing an issue where a CPU running perf eventually hangs.
Traces show timer interrupts happening every 4 seconds even
when a userspace task is running on the CPU. /proc/timer_list
also shows pending hrtimers have not run in over an hour,
including the scheduler.
Looking closer, decrementers_next_tb is getting set to
0xffffffffffffffff, and at that point we will never take
a timer interrupt again.
In __timer_interrupt() we set decrementers_next_tb to
0xffffffffffffffff and rely on ->event_handler to update it:
*next_tb = ~(u64)0;
if (evt->event_handler)
evt->event_handler(evt);
In this case ->event_handler is hrtimer_interrupt. This will eventually
call back through the clockevents code with the next event to be
programmed:
static int decrementer_set_next_event(unsigned long evt,
struct clock_event_device *dev)
{
/* Don't adjust the decrementer if some irq work is pending */
if (test_irq_work_pending())
return 0;
__get_cpu_var(decrementers_next_tb) = get_tb_or_rtc() + evt;
If irq work came in between these two points, we will return
before updating decrementers_next_tb and we never process a timer
interrupt again.
This looks to have been introduced by 0215f7d8c53f (powerpc: Fix races
with irq_work). Fix it by removing the early exit and relying on
code later on in the function to force an early decrementer:
/* We may have raced with new irq work */
if (test_irq_work_pending())
set_dec(1);
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/powerpc/kernel/time.c | 3 |
1 files changed, 0 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index b3dab20acf3..57d4bada19b 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -805,9 +805,6 @@ static void __init clocksource_init(void) static int decrementer_set_next_event(unsigned long evt, struct clock_event_device *dev) { - /* Don't adjust the decrementer if some irq work is pending */ - if (test_irq_work_pending()) - return 0; __get_cpu_var(decrementers_next_tb) = get_tb_or_rtc() + evt; set_dec(evt); |