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Commit 8e56f33f authored by John Stultz's avatar John Stultz Committed by Ingo Molnar
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clocksource: Improve comment explaining clocks_calc_max_nsecs()'s 50% safety margin 



Ingo noted that the description of clocks_calc_max_nsecs()'s
50% safety margin was somewhat circular. So this patch tries
to improve the comment to better explain what we mean by the
50% safety margin and why we need it.

Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-20-git-send-email-john.stultz@linaro.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0fa88cb4

kernel/time/clocksource.c

+5 −2
Original line number Diff line number Diff line
@@ -472,8 +472,11 @@ static u32 clocksource_max_adjustment(struct clocksource *cs) 
 * @max_cyc:	maximum cycle value before potential overflow (does not include

 *		any safety margin)

 *

 * NOTE: This function includes a safety margin of 50%, so that bad clock values

 * can be detected.

 * NOTE: This function includes a safety margin of 50%, in other words, we

 * return half the number of nanoseconds the hardware counter can technically

 * cover. This is done so that we can potentially detect problems caused by

 * delayed timers or bad hardware, which might result in time intervals that

 * are larger then what the math used can handle without overflows.

 */

u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)

{