Commit-ID: cadefd3d6cc914d95163ba1eda766bfe7ce1e5b7 Gitweb: http://git.kernel.org/tip/cadefd3d6cc914d95163ba1eda766bfe7ce1e5b7 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Thu, 27 Feb 2014 10:40:35 +0100 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Fri, 18 Apr 2014 12:07:21 +0200 sched: Make scale_rt_power() deal with backward clocks Mike reported that, while unlikely, its entirely possible for scale_rt_power() to see the time go backwards. This yields rather 'interesting' results. So like all other sites that deal with clocks; make this one ignore backward clock movement too. Reported-by: Mike Galbraith <bitbucket@xxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/20140227094035.GZ9987@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/fair.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7570dd9..5e157f1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5564,6 +5564,7 @@ static unsigned long scale_rt_power(int cpu) { struct rq *rq = cpu_rq(cpu); u64 total, available, age_stamp, avg; + s64 delta; /* * Since we're reading these variables without serialization make sure @@ -5572,7 +5573,11 @@ static unsigned long scale_rt_power(int cpu) age_stamp = ACCESS_ONCE(rq->age_stamp); avg = ACCESS_ONCE(rq->rt_avg); - total = sched_avg_period() + (rq_clock(rq) - age_stamp); + delta = rq_clock(rq) - age_stamp; + if (unlikely(delta < 0)) + delta = 0; + + total = sched_avg_period() + delta; if (unlikely(total < avg)) { /* Ensures that power won't end up being negative */ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html