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SubjectRe: [RFC][PATCH 4/7] sched, rt: Fix rq->rt.pushable_tasks bug in push_rt_task()
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On Thu, 2011-06-16 at 21:55 -0400, Steven Rostedt wrote:
> plain text document attachment
> (0004-sched-rt-Fix-rq-rt.pushable_tasks-bug-in-push_rt_tas.patch)
> From: Hillf Danton <dhillf@gmail.com>
>
> Do not call dequeue_pushable_task() when failing to push an eligible
> task, as it remains pushable, merely not at this particular moment.
>
> Cc: Yong Zhang <yong.zhang0@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Hillf Danton <dhillf@gmail.com>
> Signed-off-by: Mike Galbraith <mgalbraith@gmx.de>

Mixing addresses doesn't work. Less bouncy SOB.

Signed-off-by: Mike Galbraith <efault@gmx.de>


> Link: http://lkml.kernel.org/r/1306895385.4791.26.camel@marge.simson.net
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> kernel/sched_rt.c | 15 ++++++++-------
> 1 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
> index a6f1f64..7737d41 100644
> --- a/kernel/sched_rt.c
> +++ b/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)




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