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    Subject[PATCH v2 3/5] sched: Remove double_rq_lock() from __migrate_task()
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    Let's use ONRQ_MIGRATING instead.

    Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
    ---
    kernel/sched/core.c | 23 +++++++++++++++--------
    1 file changed, 15 insertions(+), 8 deletions(-)

    diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    index 772f791..9bfc4a9 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -4693,20 +4693,20 @@ EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
    */
    static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
    {
    - struct rq *rq_dest, *rq_src;
    + struct rq *rq;
    int ret = 0;

    if (unlikely(!cpu_active(dest_cpu)))
    return ret;

    - rq_src = cpu_rq(src_cpu);
    - rq_dest = cpu_rq(dest_cpu);
    + rq = cpu_rq(src_cpu);

    raw_spin_lock(&p->pi_lock);
    - double_rq_lock(rq_src, rq_dest);
    + raw_spin_lock(&rq->lock);
    /* Already moved. */
    if (task_cpu(p) != src_cpu)
    goto done;
    +
    /* Affinity changed (again). */
    if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
    goto fail;
    @@ -4716,15 +4716,22 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
    * placed properly.
    */
    if (task_queued(p)) {
    - dequeue_task(rq_src, p, 0);
    + dequeue_task(rq, p, 0);
    + p->on_rq = ONRQ_MIGRATING;
    set_task_cpu(p, dest_cpu);
    - enqueue_task(rq_dest, p, 0);
    - check_preempt_curr(rq_dest, p, 0);
    + raw_spin_unlock(&rq->lock);
    +
    + rq = cpu_rq(dest_cpu);
    + raw_spin_lock(&rq->lock);
    + BUG_ON(task_rq(p) != rq);
    + p->on_rq = ONRQ_QUEUED;
    + enqueue_task(rq, p, 0);
    + check_preempt_curr(rq, p, 0);
    }
    done:
    ret = 1;
    fail:
    - double_rq_unlock(rq_src, rq_dest);
    + raw_spin_unlock(&rq->lock);
    raw_spin_unlock(&p->pi_lock);
    return ret;
    }


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