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uml: deal with host time going backwards
Protection against the host's time going backwards (eg, ntp activity on the host) by keeping track of the time at the last tick and if it's greater than the current time, keep time stopped until the host catches up. Cc: Nix <nix@esperi.org.uk> Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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1 changed files with 7 additions and 0 deletions
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@ -106,6 +106,10 @@ static void deliver_alarm(void)
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unsigned long long this_tick = os_nsecs();
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int one_tick = UM_NSEC_PER_SEC / UM_HZ;
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/* Protection against the host's time going backwards */
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if ((last_tick != 0) && (this_tick < last_tick))
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this_tick = last_tick;
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if (last_tick == 0)
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last_tick = this_tick - one_tick;
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@ -148,6 +152,9 @@ static int after_sleep_interval(struct timespec *ts)
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start_usecs = usec;
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start_usecs -= skew / UM_NSEC_PER_USEC;
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if (start_usecs < 0)
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start_usecs = 0;
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tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC,
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.tv_usec = start_usecs % UM_USEC_PER_SEC });
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interval = ((struct itimerval) { { 0, usec }, tv });
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