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authorKevin Hilman <khilman@linaro.org>2014-01-15 14:51:38 +0100
committerFrederic Weisbecker <fweisbec@gmail.com>2014-01-16 00:08:12 +0100
commit8fe8ff09ce3b5750e1f3e45a1f4a81d59c7ff1f1 (patch)
tree213e7ac5b96c59f82d49ef72285ddceace6d79a9 /kernel
parente9a2eb403bd953788cd2abfd0d2646d43bd22671 (diff)
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sched/nohz: Fix overflow error in scheduler_tick_max_deferment()
While calculating the scheduler tick max deferment, the delta is converted from microseconds to nanoseconds through a multiplication against NSEC_PER_USEC. But this microseconds operand is an unsigned int, thus the result may likely overflow. The result is cast to u64 but only once the operation is completed, which is too late to avoid overflown result. This is currently not a problem because the scheduler tick max deferment is 1 second. But this may become an issue as we plan to make this value tunable. So lets fix this by casting the usecs value to u64 before multiplying by NSECS_PER_USEC. Also to prevent from this kind of mistake to happen again, move this ad-hoc jiffies -> nsecs conversion to a new helper. Signed-off-by: Kevin Hilman <khilman@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Alex Shi <alex.shi@linaro.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Kevin Hilman <khilman@linaro.org> Link: http://lkml.kernel.org/r/1387315388-31676-2-git-send-email-khilman@linaro.org [move ad-hoc conversion to jiffies_to_nsecs helper] Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/core.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a88f4a485c5e..61e601fc2b1e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2325,7 +2325,7 @@ u64 scheduler_tick_max_deferment(void)
if (time_before_eq(next, now))
return 0;
- return jiffies_to_usecs(next - now) * NSEC_PER_USEC;
+ return jiffies_to_nsecs(next - now);
}
#endif