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    Subject[PATCH 3.10 119/139] workqueue: implicit ordered attribute should be overridable
    Date
    From: Tejun Heo <tj@kernel.org>

    commit 0a94efb5acbb6980d7c9ab604372d93cd507e4d8 upstream.

    5c0338c68706 ("workqueue: restore WQ_UNBOUND/max_active==1 to be
    ordered") automatically enabled ordered attribute for unbound
    workqueues w/ max_active == 1. Because ordered workqueues reject
    max_active and some attribute changes, this implicit ordered mode
    broke cases where the user creates an unbound workqueue w/ max_active
    == 1 and later explicitly changes the related attributes.

    This patch distinguishes explicit and implicit ordered setting and
    overrides from attribute changes if implict.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Fixes: 5c0338c68706 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")
    Cc: Holger Hoffstätte <holger@applied-asynchrony.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    include/linux/workqueue.h | 4 +++-
    kernel/workqueue.c | 13 +++++++++----
    2 files changed, 12 insertions(+), 5 deletions(-)

    diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
    index 120dd35..4dab847 100644
    --- a/include/linux/workqueue.h
    +++ b/include/linux/workqueue.h
    @@ -306,6 +306,7 @@ enum {

    __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */
    __WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */
    + __WQ_ORDERED_EXPLICIT = 1 << 18, /* internal: alloc_ordered_workqueue() */

    WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
    WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */
    @@ -408,7 +409,8 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
    * Pointer to the allocated workqueue on success, %NULL on failure.
    */
    #define alloc_ordered_workqueue(fmt, flags, args...) \
    - alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)
    + alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | \
    + __WQ_ORDERED_EXPLICIT | (flags), 1, ##args)

    #define create_workqueue(name) \
    alloc_workqueue((name), WQ_MEM_RECLAIM, 1)
    diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    index 3f8558f..f55fbfa 100644
    --- a/kernel/workqueue.c
    +++ b/kernel/workqueue.c
    @@ -3399,7 +3399,7 @@ int workqueue_sysfs_register(struct workqueue_struct *wq)
    * attributes breaks ordering guarantee. Disallow exposing ordered
    * workqueues.
    */
    - if (WARN_ON(wq->flags & __WQ_ORDERED))
    + if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
    return -EINVAL;

    wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
    @@ -3964,8 +3964,12 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
    return -EINVAL;

    /* creating multiple pwqs breaks ordering guarantee */
    - if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
    - return -EINVAL;
    + if (!list_empty(&wq->pwqs)) {
    + if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
    + return -EINVAL;
    +
    + wq->flags &= ~__WQ_ORDERED;
    + }

    pwq_tbl = kzalloc(wq_numa_tbl_len * sizeof(pwq_tbl[0]), GFP_KERNEL);
    new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
    @@ -4411,13 +4415,14 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
    struct pool_workqueue *pwq;

    /* disallow meddling with max_active for ordered workqueues */
    - if (WARN_ON(wq->flags & __WQ_ORDERED))
    + if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
    return;

    max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);

    mutex_lock(&wq->mutex);

    + wq->flags &= ~__WQ_ORDERED;
    wq->saved_max_active = max_active;

    for_each_pwq(pwq, wq)
    --
    2.8.0.rc2.1.gbe9624a
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