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    Subject[PATCH 10/21] workqueue: use rcu_read_lock_sched() instead for accessing pwq in RCU
    Date
    rcu_read_lock_sched() is better than preempt_disable() if the code is
    protected by RCU_SCHED.

    Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
    ---
    kernel/workqueue.c | 10 +++++-----
    1 files changed, 5 insertions(+), 5 deletions(-)

    diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    index ad190cd..469269e 100644
    --- a/kernel/workqueue.c
    +++ b/kernel/workqueue.c
    @@ -3967,7 +3967,7 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq)
    struct pool_workqueue *pwq;
    bool ret;

    - preempt_disable();
    + rcu_read_lock_sched();

    if (!(wq->flags & WQ_UNBOUND))
    pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
    @@ -3975,7 +3975,7 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq)
    pwq = first_pwq(wq);

    ret = !list_empty(&pwq->delayed_works);
    - preempt_enable();
    + rcu_read_unlock_sched();

    return ret;
    }
    @@ -4361,16 +4361,16 @@ bool freeze_workqueues_busy(void)
    * nr_active is monotonically decreasing. It's safe
    * to peek without lock.
    */
    - preempt_disable();
    + rcu_read_lock_sched();
    for_each_pwq(pwq, wq) {
    WARN_ON_ONCE(pwq->nr_active < 0);
    if (pwq->nr_active) {
    busy = true;
    - preempt_enable();
    + rcu_read_unlock_sched();
    goto out_unlock;
    }
    }
    - preempt_enable();
    + rcu_read_unlock_sched();
    }
    out_unlock:
    mutex_unlock(&wqs_mutex);
    --
    1.7.7.6


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