From d7d8294415f0ce4254827d4a2a5ee88b00be52a8 Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Wed, 5 Jan 2011 05:41:17 +0100 Subject: sched: Fix signed unsigned comparison in check_preempt_tick() Signed unsigned comparison may lead to superfluous resched if leftmost is right of the current task, wasting a few cycles, and inadvertently _lengthening_ the current task's slice. Reported-by: Venkatesh Pallipadi Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra LKML-Reference: <1294202477.9384.5.camel@marge.simson.net> Signed-off-by: Ingo Molnar diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 414145c..77e9166 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1062,6 +1062,9 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) struct sched_entity *se = __pick_next_entity(cfs_rq); s64 delta = curr->vruntime - se->vruntime; + if (delta < 0) + return; + if (delta > ideal_runtime) resched_task(rq_of(cfs_rq)->curr); } -- cgit v0.10.2