Commit:     63070a79ba482c274bad10ac8c4b587a3e011f2c
Parent:     5a7780e725d1bb4c3094fcc12f1c5c5faea1e988
Author:     Thomas Gleixner <[EMAIL PROTECTED]>
AuthorDate: Thu Feb 14 00:58:36 2008 +0100
Committer:  Thomas Gleixner <[EMAIL PROTECTED]>
CommitDate: Thu Feb 14 22:08:30 2008 +0100

    hrtimer: catch expired CLOCK_REALTIME timers early
    A CLOCK_REALTIME timer, which has an absolute expiry time less than
    the clock realtime offset calls with a negative delta into the clock
    events code and triggers the WARN_ON() there.
    This is a false positive and needs to be prevented. Check the result
    of timer->expires - timer->base->offset right away and return -ETIME
    right away.
    Thanks to Frans Pop, who reported the problem and tested the fixes.
    Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
    Tested-by: Frans Pop <[EMAIL PROTECTED]>
 kernel/hrtimer.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index c2893af..98bee01 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -442,6 +442,8 @@ static int hrtimer_reprogram(struct hrtimer *timer,
        ktime_t expires = ktime_sub(timer->expires, base->offset);
        int res;
+       WARN_ON_ONCE(timer->expires.tv64 < 0);
         * When the callback is running, we do not reprogram the clock event
         * device. The timer callback is either running on a different CPU or
@@ -452,6 +454,15 @@ static int hrtimer_reprogram(struct hrtimer *timer,
        if (hrtimer_callback_running(timer))
                return 0;
+       /*
+        * CLOCK_REALTIME timer might be requested with an absolute
+        * expiry time which is less than base->offset. Nothing wrong
+        * about that, just avoid to call into the tick code, which
+        * has now objections against negative expiry values.
+        */
+       if (expires.tv64 < 0)
+               return -ETIME;
        if (expires.tv64 >= expires_next->tv64)
                return 0;
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