Messages in this thread Patch in this message | | | Date | Thu, 21 Jul 2011 18:27:57 GMT | From | tip-bot for Paul Turner <> | Subject | [tip:sched/core] sched: update correct entity's runtime in check_preempt_wakeup() |
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Commit-ID: 9bbd7374361d9bfc75108c3ad1c1b6db28b1be59 Gitweb: http://git.kernel.org/tip/9bbd7374361d9bfc75108c3ad1c1b6db28b1be59 Author: Paul Turner <pjt@google.com> AuthorDate: Tue, 5 Jul 2011 19:07:21 -0700 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Thu, 21 Jul 2011 18:01:43 +0200
sched: update correct entity's runtime in check_preempt_wakeup()
While looking at check_preempt_wakeup() I realized that we are potentially updating the wrong entity in the fair-group scheduling case. In this case the current task's cfs_rq may not be the same as the one used for the comparison between the waking task and the existing task's vruntime.
This potentially results in us using a stale vruntime in the pre-emption decision, providing a small false preference for the previous task. The effects of this are bounded since we always perform a hierarchal update on the tick.
Signed-off-by: Paul Turner <pjt@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/CAPM31R+2Ke2urUZKao5W92_LupdR4AYEv-EZWiJ3tG=tEes2cw@mail.gmail.com Signed-off-by: Ingo Molnar <mingo@elte.hu> --- kernel/sched_fair.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index e7d67a9..f88720b 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1919,8 +1919,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ if (!sched_feat(WAKEUP_PREEMPT)) return; - update_curr(cfs_rq); find_matching_se(&se, &pse); + update_curr(cfs_rq_of(se)); BUG_ON(!pse); if (wakeup_preempt_entity(se, pse) == 1) { /*
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