lkml.org 
[lkml]   [2011]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Subject[PATCH] sched, rt: fix rq->rt.pushable_tasks bug in push_rt_task()
    From
    Date
    On Tue, 2011-05-31 at 11:08 -0400, Steven Rostedt wrote:
    > On Tue, 2011-05-31 at 21:56 +0800, Hillf Danton wrote:
    > > On Tue, May 31, 2011 at 3:36 PM, Mike Galbraith <efault@gmx.de> wrote:
    > > > On Mon, 2011-05-30 at 21:39 +0800, Hillf Danton wrote:
    > > >> When pushing, if a pushable task could not be pushed, it is dequeued with no
    > > >> updating the rt_nr_migratory element of RT run-queue, then rt_nr_migratory is
    > > >> corrupted, which is fixed by removing the dequeue operation.
    > > >
    > > > Hm. I think you're right that this dequeue_pushable_task() call can be
    > > > removed, at least I didn't see it's reason for existing. I'd word it a
    > > > bit differently though, and not return 1 unless we really did push.
    > > >
    > >
    > > Hi Mike
    > >
    > > Your message shows what is called professional work, but something lost,
    > >
    > > > From: Hillf Danton <dhillf@gmail.com>
    > > >
    > > > sched, rt: fix rq->rt.pushable_tasks bug in push_rt_task()
    > > >
    > > > Do not call dequeue_pushable_task() when failing to push an eligible
    > > > task, as it remains pushable, merely not at this particular moment.
    > > >
    > > > Signed-off-by: Hillf Danton <dhillf@gmail.com>
    > >
    > > Signed-off-by: Mike Galbraith <efault@gmx.de>
    > >
    >
    > Yeah, Mike, can you remail this adding your SOB too. You can keep
    > Hillf's SOB as well, since both of you made changes.

    From: Hillf Danton <dhillf@gmail.com>
    AuthorDate: Mon, 30 May 2011 21:39:50 +0800

    sched, rt: fix rq->rt.pushable_tasks bug in push_rt_task()

    Do not call dequeue_pushable_task() when failing to push an eligible
    task, as it remains pushable until either it's cpumask says otherwise,
    or is selected. It is merely not pushable at this particular moment.

    Signed-off-by: Hillf Danton <dhillf@gmail.com>
    Signed-off-by: Mike Galbraith <efault@gmx.de>
    ---
    kernel/sched_rt.c | 15 ++++++++-------
    1 file changed, 8 insertions(+), 7 deletions(-)

    Index: linux-2.6.40.git/kernel/sched_rt.c
    ===================================================================
    --- linux-2.6.40.git.orig/kernel/sched_rt.c
    +++ linux-2.6.40.git/kernel/sched_rt.c
    @@ -1378,6 +1378,7 @@ static int push_rt_task(struct rq *rq)
    {
    struct task_struct *next_task;
    struct rq *lowest_rq;
    + int ret = 0;

    if (!rq->rt.overloaded)
    return 0;
    @@ -1410,7 +1411,7 @@ retry:
    if (!lowest_rq) {
    struct task_struct *task;
    /*
    - * find lock_lowest_rq releases rq->lock
    + * find_lock_lowest_rq releases rq->lock
    * so it is possible that next_task has migrated.
    *
    * We need to make sure that the task is still on the same
    @@ -1420,12 +1421,11 @@ retry:
    task = pick_next_pushable_task(rq);
    if (task_cpu(next_task) == rq->cpu && task == next_task) {
    /*
    - * If we get here, the task hasn't moved at all, but
    - * it has failed to push. We will not try again,
    - * since the other cpus will pull from us when they
    - * are ready.
    + * The task hasn't migrated, and is still the next
    + * eligible task, but we failed to find a run-queue
    + * to push it to. Do not retry in this case, since
    + * other cpus will pull from us when ready.
    */
    - dequeue_pushable_task(rq, next_task);
    goto out;
    }

    @@ -1444,6 +1444,7 @@ retry:
    deactivate_task(rq, next_task, 0);
    set_task_cpu(next_task, lowest_rq->cpu);
    activate_task(lowest_rq, next_task, 0);
    + ret = 1;

    resched_task(lowest_rq->curr);

    @@ -1452,7 +1453,7 @@ retry:
    out:
    put_task_struct(next_task);

    - return 1;
    + return ret;
    }

    static void push_rt_tasks(struct rq *rq)



    \
     
     \ /
      Last update: 2011-06-01 04:17    [W:0.026 / U:0.556 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site