From mboxrd@z Thu Jan 1 00:00:00 1970 From: yangyingliang@huawei.com (Yang Yingliang) Date: Tue, 27 Oct 2015 21:21:11 +0800 Subject: [PATCH 0/2] validate the delta of cycle_now and cycle_last on arm64 Message-ID: <1445952073-7260-1-git-send-email-yangyingliang@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org In multi-core system, if the clock is not sync perfectly, it will make cycle_last that recorded by CPU-A is a little more than cycle_now that read by CPU-B. With the negative result, hrtimer_update_base() return a huge and wrong time. It leads to the cpu can not finish the while loop in hrtimer_interrupt() until the real nowtime which is returned from ktime_get() catch up with the wrong time on clock monotonic base. Fix it by select config CLOCKSOURCE_VALIDATE_LAST_CYCLE. Cc: Thomas Gleixner Yang Yingliang (2): clocksource: replace cycle_last validation with an equal way arm64: validate the cycle_last to prevent time going backwards arch/arm64/Kconfig | 1 + kernel/time/timekeeping_internal.h | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-) -- 2.5.0