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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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