Commit-ID: 8e56f33f8439b2f8e7f4ae7f3d0bfe683ecc3b09 Gitweb: http://git.kernel.org/tip/8e56f33f8439b2f8e7f4ae7f3d0bfe683ecc3b09 Author: John Stultz <john.stu...@linaro.org> AuthorDate: Wed, 1 Apr 2015 20:34:39 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Fri, 3 Apr 2015 08:18:35 +0200
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: John Stultz <john.stu...@linaro.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Prarit Bhargava <pra...@redhat.com> Cc: Richard Cochran <richardcoch...@gmail.com> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/1427945681-29972-20-git-send-email-john.stu...@linaro.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/time/clocksource.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index c3be3c7..15facb1 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -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) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
