From bbdf9b9a28729ed1dd211368f76baef051aaecae Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Tue, 5 Aug 2008 16:14:06 -0400 Subject: uml: deal with host time going backwards commit 06e1e4ffbd1932e288839b3140cda6b8141eb684 upstream 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 Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/um/os-Linux/time.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c index bee98f466d66..dec5678fc17f 100644 --- a/arch/um/os-Linux/time.c +++ b/arch/um/os-Linux/time.c @@ -106,6 +106,10 @@ static void deliver_alarm(void) unsigned long long this_tick = os_nsecs(); 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) last_tick = this_tick - one_tick; @@ -148,6 +152,9 @@ static int after_sleep_interval(struct timespec *ts) start_usecs = 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_usec = start_usecs % UM_USEC_PER_SEC }); interval = ((struct itimerval) { { 0, usec }, tv }); -- cgit v1.2.3