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[PATCH resend] clocksource: modify the cycle_last validation to fit for non-64bit clocksourece mask

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From: Yang Yingliang <yangyingliang@huawei.com>

Check the delta of now and last to make sure it's not
negative while the clocksource mask is not 64-bits.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
  kernel/time/timekeeping_internal.h | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/time/timekeeping_internal.h 
b/kernel/time/timekeeping_internal.h
index 4ea005a..cbfcd2d 100644
--- a/kernel/time/timekeeping_internal.h
+++ b/kernel/time/timekeeping_internal.h
@@ -16,8 +16,9 @@ extern void tk_debug_account_sleep_time(struct 
timespec64 *t);
  static inline cycle_t clocksource_delta(cycle_t now, cycle_t last, 
cycle_t mask)
  {
  	cycle_t ret = (now - last) & mask;
+	cycle_t negative = ret & ~(mask >> 1);

-	return (s64) ret > 0 ? ret : 0;
+	return negative ? 0 : ret;
  }
  #else
  static inline cycle_t clocksource_delta(cycle_t now, cycle_t last, 
cycle_t mask)
-- 
2.5.0

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[PATCH 0/2] validate the delta of cycle_now and cycle_last on arm64 Yang Yingliang <yangyingliang@huawei.com> - 2015-10-27 14:30 +0100
  [PATCH 2/2] arm64: validate the delta of cycle_now and cycle_last Yang Yingliang <yangyingliang@huawei.com> - 2015-10-27 14:30 +0100
    Re: [PATCH 2/2] arm64: validate the delta of cycle_now and cycle_last Mark Rutland <mark.rutland@arm.com> - 2015-10-27 15:10 +0100
      Re: [PATCH 2/2] arm64: validate the delta of cycle_now and cycle_last Ding Tianhong <dingtianhong@huawei.com> - 2015-10-28 02:40 +0100
      Re: [PATCH 2/2] arm64: validate the delta of cycle_now and cycle_last Yang Yingliang <yangyingliang@huawei.com> - 2015-10-29 08:40 +0100
        Re: [PATCH 2/2] arm64: validate the delta of cycle_now and cycle_last Yang Yingliang <yangyingliang@huawei.com> - 2015-10-29 09:40 +0100
  [PATCH 1/2] clocksource: replace cycle_last validation with an equal way Yang Yingliang <yangyingliang@huawei.com> - 2015-10-27 14:30 +0100
    Re: [PATCH 1/2] clocksource: replace cycle_last validation with an  equal way Thomas Gleixner <tglx@linutronix.de> - 2015-10-30 16:00 +0100
      Re: [PATCH 1/2] clocksource: replace cycle_last validation with an  equal way Yang Yingliang <yangyingliang@huawei.com> - 2015-10-31 11:10 +0100
      [PATCH resend] clocksource: modify the cycle_last validation to fit  for non-64bit clocksourece mask Yang Yingliang <yangyingliang@huawei.com> - 2015-10-31 11:30 +0100

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