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authorThomas Gleixner <tglx@linutronix.de>2007-05-30 01:47:39 +0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-30 05:11:10 +0400
commiteaad084bb0f3a6259e56400cd45d061dbf040600 (patch)
tree34a5f5c3e1a849b035510ee28d5aaffd42a36dcc /include/linux/timer.h
parent6e98ee75c3ab99db48ecc0615c2246dc193111a9 (diff)
downloadlinux-eaad084bb0f3a6259e56400cd45d061dbf040600.tar.xz
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.h6
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:
*/