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>
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index bee98f4..dec5678 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -106,6 +106,10 @@
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 @@
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 });