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Message-ID: <533414C7.1050607@cn.fujitsu.com>
Date: Thu, 27 Mar 2014 20:08:39 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Lai Jiangshan <laijs@...fujitsu.com>
CC: Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: add __WQ_FREEZING and remove POOL_FREEZING
On 03/25/2014 05:56 PM, Lai Jiangshan wrote:
> freezing is nothing related to pools, but POOL_FREEZING adds a connection,
> and causes freeze_workqueues_begin() and thaw_workqueues() complicated.
>
> Since freezing is workqueue instance attribute, so we introduce __WQ_FREEZING
> to wq->flags instead and remove POOL_FREEZING.
>
> we set __WQ_FREEZING only when freezable(to simplify pwq_adjust_max_active()),
> make freeze_workqueues_begin() and thaw_workqueues() fast skip non-freezable wq.
>
> Changed from previous patches(requested by tj):
> 1) added the WARN_ON_ONCE() back
> 2) merged the two patches as one
Ping.
Hi, Tejun
You had reviewed this patch several rounds.
I had applied all your requests(the last two is listed above) in your comments.
I'm deeply sorry for responding so late.
Thanks,
Lai
>
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> ---
> include/linux/workqueue.h | 1 +
> kernel/workqueue.c | 43 ++++++++++++-------------------------------
> 2 files changed, 13 insertions(+), 31 deletions(-)
>
> diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
> index 704f4f6..a45202b 100644
> --- a/include/linux/workqueue.h
> +++ b/include/linux/workqueue.h
> @@ -335,6 +335,7 @@ enum {
> */
> WQ_POWER_EFFICIENT = 1 << 7,
>
> + __WQ_FREEZING = 1 << 15, /* internel: workqueue is freezing */
> __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */
> __WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 193e977..0c74979 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -70,7 +70,6 @@ enum {
> */
> POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
> POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
> - POOL_FREEZING = 1 << 3, /* freeze in progress */
>
> /* worker flags */
> WORKER_STARTED = 1 << 0, /* started */
> @@ -3632,9 +3631,6 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
> if (!pool || init_worker_pool(pool) < 0)
> goto fail;
>
> - if (workqueue_freezing)
> - pool->flags |= POOL_FREEZING;
> -
> lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
> copy_workqueue_attrs(pool->attrs, attrs);
>
> @@ -3730,18 +3726,13 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
> static void pwq_adjust_max_active(struct pool_workqueue *pwq)
> {
> struct workqueue_struct *wq = pwq->wq;
> - bool freezable = wq->flags & WQ_FREEZABLE;
>
> - /* for @wq->saved_max_active */
> + /* for @wq->saved_max_active and @wq->flags */
> lockdep_assert_held(&wq->mutex);
>
> - /* fast exit for non-freezable wqs */
> - if (!freezable && pwq->max_active == wq->saved_max_active)
> - return;
> -
> spin_lock_irq(&pwq->pool->lock);
>
> - if (!freezable || !(pwq->pool->flags & POOL_FREEZING)) {
> + if (!(wq->flags & __WQ_FREEZING)) {
> pwq->max_active = wq->saved_max_active;
>
> while (!list_empty(&pwq->delayed_works) &&
> @@ -4250,6 +4241,8 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
> mutex_lock(&wq_pool_mutex);
>
> mutex_lock(&wq->mutex);
> + if ((wq->flags & WQ_FREEZABLE) && workqueue_freezing)
> + wq->flags |= __WQ_FREEZING;
> for_each_pwq(pwq, wq)
> pwq_adjust_max_active(pwq);
> mutex_unlock(&wq->mutex);
> @@ -4856,26 +4849,20 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
> */
> void freeze_workqueues_begin(void)
> {
> - struct worker_pool *pool;
> struct workqueue_struct *wq;
> struct pool_workqueue *pwq;
> - int pi;
>
> mutex_lock(&wq_pool_mutex);
>
> WARN_ON_ONCE(workqueue_freezing);
> workqueue_freezing = true;
>
> - /* set FREEZING */
> - for_each_pool(pool, pi) {
> - spin_lock_irq(&pool->lock);
> - WARN_ON_ONCE(pool->flags & POOL_FREEZING);
> - pool->flags |= POOL_FREEZING;
> - spin_unlock_irq(&pool->lock);
> - }
> -
> list_for_each_entry(wq, &workqueues, list) {
> + if (!(wq->flags & WQ_FREEZABLE))
> + continue;
> mutex_lock(&wq->mutex);
> + WARN_ON_ONCE(wq->flags & __WQ_FREEZING);
> + wq->flags |= __WQ_FREEZING;
> for_each_pwq(pwq, wq)
> pwq_adjust_max_active(pwq);
> mutex_unlock(&wq->mutex);
> @@ -4943,25 +4930,19 @@ void thaw_workqueues(void)
> {
> struct workqueue_struct *wq;
> struct pool_workqueue *pwq;
> - struct worker_pool *pool;
> - int pi;
>
> mutex_lock(&wq_pool_mutex);
>
> if (!workqueue_freezing)
> goto out_unlock;
>
> - /* clear FREEZING */
> - for_each_pool(pool, pi) {
> - spin_lock_irq(&pool->lock);
> - WARN_ON_ONCE(!(pool->flags & POOL_FREEZING));
> - pool->flags &= ~POOL_FREEZING;
> - spin_unlock_irq(&pool->lock);
> - }
> -
> /* restore max_active and repopulate worklist */
> list_for_each_entry(wq, &workqueues, list) {
> + if (!(wq->flags & WQ_FREEZABLE))
> + continue;
> mutex_lock(&wq->mutex);
> + WARN_ON_ONCE(!(wq->flags & __WQ_FREEZING));
> + wq->flags &= ~__WQ_FREEZING;
> for_each_pwq(pwq, wq)
> pwq_adjust_max_active(pwq);
> mutex_unlock(&wq->mutex);
--
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