Messages in this thread Patch in this message | | | Date | Tue, 13 Dec 2011 15:57:58 +0900 | From | Daisuke Nishimura <> | Subject | [PATCH 1/3] sched: fix cgroup movement of newly created process |
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There is a small race between do_fork() and sched_move_task(), which is trying to move the child.
do_fork() sched_move_task() --------------------------------+--------------------------------- copy_process() sched_fork() task_fork_fair() -> vruntime of the child is initialized based on that of the parent. -> we can see the child in "tasks" file now. task_rq_lock() task_move_group_fair() ->child.se.vruntime -= (old)cfs_rq->min_vruntime ->child.se.vruntime += (new)cfs_rq->min_vruntime task_rq_unlock() wake_up_new_task() ... enqueue_entity() child.se->vruntime += cfs_rq->min_vruntime
As a result, vruntime of the child becomes far bigger than min_vruntime, if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime.
This patch fixes this problem by just ignoring such process in task_move_group_fair(), because the vruntime has already been normalized in task_fork_fair().
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> --- kernel/sched_fair.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 5c9e679..df145a9 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -4922,10 +4922,10 @@ static void task_move_group_fair(struct task_struct *p, int on_rq) * to another cgroup's rq. This does somewhat interfere with the * fair sleeper stuff for the first placement, but who cares. */ - if (!on_rq) + if (!on_rq && p->state != TASK_RUNNING) p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime; set_task_rq(p, task_cpu(p)); - if (!on_rq) + if (!on_rq && p->state != TASK_RUNNING) p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime; } #endif -- 1.7.1
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