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authorThomas Gleixner <tglx@linutronix.de>2007-12-07 19:16:17 +0100
committerIngo Molnar <mingo@elte.hu>2007-12-07 19:16:17 +0100
commit62f0f61e6673e67151a7c8c0f9a09c7ea43fe2b5 (patch)
treec41cc826e53b7ce726e6f343a0ab72ad7e058ca4 /kernel/hrtimer.c
parentf194d132e4971111f85c18c96067acffb13cee6d (diff)
downloadlwn-62f0f61e6673e67151a7c8c0f9a09c7ea43fe2b5.tar.gz
lwn-62f0f61e6673e67151a7c8c0f9a09c7ea43fe2b5.zip
hrtimers: avoid overflow for large relative timeouts
Relative hrtimers with a large timeout value might end up as negative timer values, when the current time is added in hrtimer_start(). This in turn is causing the clockevents_set_next() function to set an huge timeout and sleep for quite a long time when we have a clock source which is capable of long sleeps like HPET. With PIT this almost goes unnoticed as the maximum delta is ~27ms. The non-hrt/nohz code sorts this out in the next timer interrupt, so we never noticed that problem which has been there since the first day of hrtimers. This bug became more apparent in 2.6.24 which activates HPET on more hardware. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/hrtimer.c')
-rw-r--r--kernel/hrtimer.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 22a25142e4cf..e65dd0b47cdc 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -850,6 +850,14 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
#ifdef CONFIG_TIME_LOW_RES
tim = ktime_add(tim, base->resolution);
#endif
+ /*
+ * Careful here: User space might have asked for a
+ * very long sleep, so the add above might result in a
+ * negative number, which enqueues the timer in front
+ * of the queue.
+ */
+ if (tim.tv64 < 0)
+ tim.tv64 = KTIME_MAX;
}
timer->expires = tim;