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hrtimer: catch expired CLOCK_REALTIME timers early 

A CLOCK_REALTIME timer, which has an absolute expiry time less than
the clock realtime offset calls with a negative delta into the clock
events code and triggers the WARN_ON() there.

This is a false positive and needs to be prevented. Check the result
of timer->expires - timer->base->offset right away and return -ETIME
right away.

Thanks to Frans Pop, who reported the problem and tested the fixes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Frans Pop <elendil@planet.nl>
This commit is contained in:
Thomas Gleixner 2008-02-14 00:58:36 +01:00
parent 5a7780e725
commit 63070a79ba
1 changed files with 11 additions and 0 deletions
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11
kernel/hrtimer.c
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@ -442,6 +442,8 @@ static int hrtimer_reprogram(struct hrtimer *timer,
ktime_t expires = ktime_sub(timer->expires, base->offset);
int res;
WARN_ON_ONCE(timer->expires.tv64 < 0);
/*
* When the callback is running, we do not reprogram the clock event
* device. The timer callback is either running on a different CPU or
@ -452,6 +454,15 @@ static int hrtimer_reprogram(struct hrtimer *timer,
if (hrtimer_callback_running(timer))
return 0;
/*
* CLOCK_REALTIME timer might be requested with an absolute
* expiry time which is less than base->offset. Nothing wrong
* about that, just avoid to call into the tick code, which
* has now objections against negative expiry values.
*/
if (expires.tv64 < 0)
return -ETIME;
if (expires.tv64 >= expires_next->tv64)
return 0;