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Subject[PATCH 1/6] UML - Deal with host time going backwards
Protection against the host's time going backwards - keep 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>
---
arch/um/os-Linux/time.c | 7 +++++++
1 file changed, 7 insertions(+)
Index: linux-2.6-git/arch/um/os-Linux/time.c
===================================================================
--- linux-2.6-git.orig/arch/um/os-Linux/time.c 2008-05-14 10:44:02.000000000 -0400
+++ linux-2.6-git/arch/um/os-Linux/time.c 2008-06-02 15:43:53.000000000 -0400
@@ -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 t
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 });

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