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| author | Thomas Gleixner <tglx@linutronix.de> | 2007-05-29 23:47:39 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-29 18:11:10 -0700 |
| commit | eaad084bb0f3a6259e56400cd45d061dbf040600 (patch) | |
| tree | 34a5f5c3e1a849b035510ee28d5aaffd42a36dcc /include/linux/timer.h | |
| parent | 6e98ee75c3ab99db48ecc0615c2246dc193111a9 (diff) | |
| download | linux-stable-eaad084bb0f3a6259e56400cd45d061dbf040600.tar.gz linux-stable-eaad084bb0f3a6259e56400cd45d061dbf040600.tar.bz2 linux-stable-eaad084bb0f3a6259e56400cd45d061dbf040600.zip | |
NOHZ: prevent multiplication overflow - stop timer for huge timeouts
get_next_timer_interrupt() returns a delta of (LONG_MAX > 1) in case
there is no timer pending. On 64 bit machines this results in a
multiplication overflow in tick_nohz_stop_sched_tick().
Reported by: Dave Miller <davem@davemloft.net>
Make the return value a constant and limit the return value to a 32 bit
value.
When the max timeout value is returned, we can safely stop the tick
timer device. The max jiffies delta results in a 12 days timeout for
HZ=1000.
In the long term the get_next_timer_interrupt() code needs to be
reworked to return ktime instead of jiffies, but we have to wait until
the last users of the original NO_IDLE_HZ code are converted.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/timer.h')
| -rw-r--r-- | include/linux/timer.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/timer.h b/include/linux/timer.h index e0c5c16c992f..c661710d3627 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -69,6 +69,12 @@ extern int __mod_timer(struct timer_list *timer, unsigned long expires); extern int mod_timer(struct timer_list *timer, unsigned long expires); /* + * The jiffies value which is added to now, when there is no timer + * in the timer wheel: + */ +#define NEXT_TIMER_MAX_DELTA ((1UL << 30) - 1) + +/* * Return when the next timer-wheel timeout occurs (in absolute jiffies), * locks the timer base: */ |