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uml: deal with host time going backwards

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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>
This commit is contained in:
Jeff Dike 2008-06-05 22:46:10 -07:00 committed by Linus Torvalds
parent 34397892a3
commit 06e1e4ffbd
1 changed files with 7 additions and 0 deletions
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7
arch/um/os-Linux/time.c
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@ -106,6 +106,10 @@ static void deliver_alarm(void)
unsigned long long this_tick = os_nsecs(); unsigned long long this_tick = os_nsecs();
int one_tick = UM_NSEC_PER_SEC / UM_HZ; int one_tick = UM_NSEC_PER_SEC / UM_HZ;
/* Protection against the host's time going backwards */
if ((last_tick != 0) && (this_tick < last_tick))
this_tick = last_tick;
if (last_tick == 0) if (last_tick == 0)
last_tick = this_tick - one_tick; last_tick = this_tick - one_tick;
@ -148,6 +152,9 @@ static int after_sleep_interval(struct timespec *ts)
start_usecs = usec; start_usecs = usec;
start_usecs -= skew / UM_NSEC_PER_USEC; start_usecs -= skew / UM_NSEC_PER_USEC;
if (start_usecs < 0)
start_usecs = 0;
tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC, tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC,
.tv_usec = start_usecs % UM_USEC_PER_SEC }); .tv_usec = start_usecs % UM_USEC_PER_SEC });
interval = ((struct itimerval) { { 0, usec }, tv }); interval = ((struct itimerval) { { 0, usec }, tv });