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    Subject[PATCH wq/for-3.6-fixes 2/3] workqueue: rename rebind_workers() to gcwq_associate() and let it handle locking and DISASSOCIATED clearing
    From 0150a04271dbcc9abbb2575911fa1d72d40451bf Mon Sep 17 00:00:00 2001
    From: Tejun Heo <tj@kernel.org>
    Date: Thu, 6 Sep 2012 12:50:40 -0700

    CPU_ONLINE used to handle locking and clearing of DISASSOCIATED and
    rebind_workers() just the rebinding. This patch renames the function
    to gcwq_associate() and let it handle the whole onlining. This is for
    the scheduled fix of a subtle idle worker depletion issue during
    CPU_ONLINE.

    Note that this removes the unnecessary relock at the end of
    gcwq_associate().

    This patch doesn't introduce any functional difference.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    kernel/workqueue.c | 29 ++++++++++++++---------------
    1 files changed, 14 insertions(+), 15 deletions(-)

    diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    index 63ede1f..b19170b 100644
    --- a/kernel/workqueue.c
    +++ b/kernel/workqueue.c
    @@ -480,6 +480,8 @@ static atomic_t unbound_pool_nr_running[NR_WORKER_POOLS] = {
    };

    static int worker_thread(void *__worker);
    +static void gcwq_claim_management(struct global_cwq *gcwq);
    +static void gcwq_release_management(struct global_cwq *gcwq);

    static int worker_pool_pri(struct worker_pool *pool)
    {
    @@ -1355,11 +1357,11 @@ static void busy_worker_rebind_fn(struct work_struct *work)
    }

    /**
    - * rebind_workers - rebind all workers of a gcwq to the associated CPU
    + * gcwq_associate - (re)associate a gcwq to its CPU and rebind its workers
    * @gcwq: gcwq of interest
    *
    - * @gcwq->cpu is coming online. Rebind all workers to the CPU. Rebinding
    - * is different for idle and busy ones.
    + * @gcwq->cpu is coming online. Clear %GCWQ_DISASSOCIATED and rebind all
    + * workers to the CPU. Rebinding is different for idle and busy ones.
    *
    * The idle ones should be rebound synchronously and idle rebinding should
    * be complete before any worker starts executing work items with
    @@ -1378,8 +1380,7 @@ static void busy_worker_rebind_fn(struct work_struct *work)
    * On return, all workers are guaranteed to either be bound or have rebind
    * work item scheduled.
    */
    -static void rebind_workers(struct global_cwq *gcwq)
    - __releases(&gcwq->lock) __acquires(&gcwq->lock)
    +static void gcwq_associate(struct global_cwq *gcwq)
    {
    struct idle_rebind idle_rebind;
    struct worker_pool *pool;
    @@ -1387,10 +1388,10 @@ static void rebind_workers(struct global_cwq *gcwq)
    struct hlist_node *pos;
    int i;

    - lockdep_assert_held(&gcwq->lock);
    + gcwq_claim_management(gcwq);
    + spin_lock_irq(&gcwq->lock);

    - for_each_worker_pool(pool, gcwq)
    - lockdep_assert_held(&pool->manager_mutex);
    + gcwq->flags &= ~GCWQ_DISASSOCIATED;

    /*
    * Rebind idle workers. Interlocked both ways. We wait for
    @@ -1477,8 +1478,11 @@ retry:
    if (--idle_rebind.cnt) {
    spin_unlock_irq(&gcwq->lock);
    wait_for_completion(&idle_rebind.done);
    - spin_lock_irq(&gcwq->lock);
    + } else {
    + spin_unlock_irq(&gcwq->lock);
    }
    +
    + gcwq_release_management(gcwq);
    }

    static struct worker *alloc_worker(void)
    @@ -3496,12 +3500,7 @@ static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,

    case CPU_DOWN_FAILED:
    case CPU_ONLINE:
    - gcwq_claim_management(gcwq);
    - spin_lock_irq(&gcwq->lock);
    - gcwq->flags &= ~GCWQ_DISASSOCIATED;
    - rebind_workers(gcwq);
    - spin_unlock_irq(&gcwq->lock);
    - gcwq_release_management(gcwq);
    + gcwq_associate(gcwq);
    break;
    }
    return NOTIFY_OK;
    --
    1.7.7.3


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