From 06e1e4ffbd1932e288839b3140cda6b8141eb684 Mon Sep 17 00:00:00 2001
From: Jeff Dike <jdike@addtoit.com>
Date: Thu, 5 Jun 2008 22:46:10 -0700
Subject: [PATCH] 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>
---
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 });
--
2.34.1