From b0a9b5111abf60ef07eade834f480e89004c7920 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 25 Jan 2009 11:31:36 +0100 Subject: [PATCH] hrtimer: prevent negative expiry value after clock_was_set() Impact: prevent false positive WARN_ON() in clockevents_program_event() clock_was_set() changes the base->offset of CLOCK_REALTIME and enforces the reprogramming of the clockevent device to expire timers which are based on CLOCK_REALTIME. If the clock change is large enough then the subtraction of the timer expiry value and base->offset can become negative which triggers the warning in clockevents_program_event(). Check the subtraction result and set a negative value to 0. Signed-off-by: Thomas Gleixner --- kernel/hrtimer.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 647a40e..f394d2a 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -501,6 +501,13 @@ static void hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base) continue; timer = rb_entry(base->first, struct hrtimer, node); expires = ktime_sub(hrtimer_get_expires(timer), base->offset); + /* + * clock_was_set() has changed base->offset so the + * result might be negative. Fix it up to prevent a + * false positive in clockevents_program_event() + */ + if (expires.tv64 < 0) + expires.tv64 = 0; if (expires.tv64 < cpu_base->expires_next.tv64) cpu_base->expires_next = expires; } -- 1.8.2.3