workqueue: separate out pool_workqueue locking into pwq_lock
This patch continues locking cleanup from the previous patch. It breaks out pool_workqueue synchronization from workqueue_lock into a new spinlock - pwq_lock. The followings are protected by pwq_lock. * workqueue->pwqs * workqueue->saved_max_active The conversion is straight-forward. workqueue_lock usages which cover the above two are converted to pwq_lock. New locking label PW added for things protected by pwq_lock and FR is updated to mean flush_mutex + pwq_lock + sched-RCU. This patch shouldn't introduce any visible behavior changes. Signed-off-by: Tejun Heo <tj@kernel.org>
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Tejun Heo
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5bcab3355a
commit
794b18bc8a
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@ -123,9 +123,11 @@ enum {
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*
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* WR: wq_mutex protected for writes. Sched-RCU protected for reads.
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*
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* PW: pwq_lock protected.
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*
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* W: workqueue_lock protected.
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*
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* FR: wq->flush_mutex and workqueue_lock protected for writes. Sched-RCU
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* FR: wq->flush_mutex and pwq_lock protected for writes. Sched-RCU
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* protected for reads.
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*/
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@ -198,7 +200,7 @@ struct pool_workqueue {
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* Release of unbound pwq is punted to system_wq. See put_pwq()
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* and pwq_unbound_release_workfn() for details. pool_workqueue
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* itself is also sched-RCU protected so that the first pwq can be
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* determined without grabbing workqueue_lock.
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* determined without grabbing pwq_lock.
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*/
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struct work_struct unbound_release_work;
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struct rcu_head rcu;
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@ -237,7 +239,7 @@ struct workqueue_struct {
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struct worker *rescuer; /* I: rescue worker */
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int nr_drainers; /* WQ: drain in progress */
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int saved_max_active; /* W: saved pwq max_active */
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int saved_max_active; /* PW: saved pwq max_active */
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#ifdef CONFIG_SYSFS
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struct wq_device *wq_dev; /* I: for sysfs interface */
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@ -251,6 +253,7 @@ struct workqueue_struct {
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static struct kmem_cache *pwq_cache;
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static DEFINE_MUTEX(wq_mutex); /* protects workqueues and pools */
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static DEFINE_SPINLOCK(pwq_lock); /* protects pool_workqueues */
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static DEFINE_SPINLOCK(workqueue_lock);
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static LIST_HEAD(workqueues); /* WQ: list of all workqueues */
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@ -291,10 +294,10 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
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lockdep_is_held(&wq_mutex), \
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"sched RCU or wq_mutex should be held")
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#define assert_rcu_or_wq_lock() \
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#define assert_rcu_or_pwq_lock() \
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rcu_lockdep_assert(rcu_read_lock_sched_held() || \
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lockdep_is_held(&workqueue_lock), \
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"sched RCU or workqueue lock should be held")
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lockdep_is_held(&pwq_lock), \
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"sched RCU or pwq_lock should be held")
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#define for_each_cpu_worker_pool(pool, cpu) \
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for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
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@ -326,16 +329,16 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
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* @pwq: iteration cursor
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* @wq: the target workqueue
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*
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* This must be called either with workqueue_lock held or sched RCU read
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* locked. If the pwq needs to be used beyond the locking in effect, the
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* caller is responsible for guaranteeing that the pwq stays online.
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* This must be called either with pwq_lock held or sched RCU read locked.
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* If the pwq needs to be used beyond the locking in effect, the caller is
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* responsible for guaranteeing that the pwq stays online.
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*
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* The if/else clause exists only for the lockdep assertion and can be
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* ignored.
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*/
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#define for_each_pwq(pwq, wq) \
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list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
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if (({ assert_rcu_or_wq_lock(); false; })) { } \
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if (({ assert_rcu_or_pwq_lock(); false; })) { } \
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else
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#ifdef CONFIG_DEBUG_OBJECTS_WORK
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@ -474,13 +477,13 @@ static int worker_pool_assign_id(struct worker_pool *pool)
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* first_pwq - return the first pool_workqueue of the specified workqueue
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* @wq: the target workqueue
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*
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* This must be called either with workqueue_lock held or sched RCU read
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* locked. If the pwq needs to be used beyond the locking in effect, the
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* caller is responsible for guaranteeing that the pwq stays online.
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* This must be called either with pwq_lock held or sched RCU read locked.
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* If the pwq needs to be used beyond the locking in effect, the caller is
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* responsible for guaranteeing that the pwq stays online.
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*/
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static struct pool_workqueue *first_pwq(struct workqueue_struct *wq)
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{
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assert_rcu_or_wq_lock();
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assert_rcu_or_pwq_lock();
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return list_first_or_null_rcu(&wq->pwqs, struct pool_workqueue,
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pwqs_node);
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}
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@ -3639,9 +3642,9 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
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* and consistent with the linking path.
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*/
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mutex_lock(&wq->flush_mutex);
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spin_lock_irq(&workqueue_lock);
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spin_lock_irq(&pwq_lock);
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list_del_rcu(&pwq->pwqs_node);
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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mutex_unlock(&wq->flush_mutex);
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put_unbound_pool(pool);
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@ -3669,7 +3672,7 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
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bool freezable = wq->flags & WQ_FREEZABLE;
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/* for @wq->saved_max_active */
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lockdep_assert_held(&workqueue_lock);
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lockdep_assert_held(&pwq_lock);
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/* fast exit for non-freezable wqs */
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if (!freezable && pwq->max_active == wq->saved_max_active)
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@ -3706,7 +3709,7 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
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INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
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mutex_lock(&wq->flush_mutex);
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spin_lock_irq(&workqueue_lock);
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spin_lock_irq(&pwq_lock);
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/*
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* Set the matching work_color. This is synchronized with
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@ -3722,7 +3725,7 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
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/* link in @pwq */
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list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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mutex_unlock(&wq->flush_mutex);
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}
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@ -3886,10 +3889,10 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
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*/
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mutex_lock(&wq_mutex);
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spin_lock_irq(&workqueue_lock);
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spin_lock_irq(&pwq_lock);
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for_each_pwq(pwq, wq)
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pwq_adjust_max_active(pwq);
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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list_add(&wq->list, &workqueues);
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@ -3920,13 +3923,13 @@ void destroy_workqueue(struct workqueue_struct *wq)
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drain_workqueue(wq);
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/* sanity checks */
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spin_lock_irq(&workqueue_lock);
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spin_lock_irq(&pwq_lock);
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for_each_pwq(pwq, wq) {
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int i;
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for (i = 0; i < WORK_NR_COLORS; i++) {
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if (WARN_ON(pwq->nr_in_flight[i])) {
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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return;
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}
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}
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@ -3934,11 +3937,11 @@ void destroy_workqueue(struct workqueue_struct *wq)
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if (WARN_ON(pwq->refcnt > 1) ||
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WARN_ON(pwq->nr_active) ||
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WARN_ON(!list_empty(&pwq->delayed_works))) {
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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return;
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}
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}
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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/*
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* wq list is used to freeze wq, remove from list after
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@ -4000,14 +4003,14 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
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max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
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spin_lock_irq(&workqueue_lock);
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spin_lock_irq(&pwq_lock);
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wq->saved_max_active = max_active;
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for_each_pwq(pwq, wq)
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pwq_adjust_max_active(pwq);
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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}
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EXPORT_SYMBOL_GPL(workqueue_set_max_active);
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@ -4266,7 +4269,7 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
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* pool->worklist.
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*
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* CONTEXT:
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* Grabs and releases wq_mutex, workqueue_lock and pool->lock's.
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* Grabs and releases wq_mutex, pwq_lock and pool->lock's.
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*/
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void freeze_workqueues_begin(void)
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{
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@ -4289,12 +4292,12 @@ void freeze_workqueues_begin(void)
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}
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/* suppress further executions by setting max_active to zero */
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spin_lock_irq(&workqueue_lock);
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spin_lock_irq(&pwq_lock);
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list_for_each_entry(wq, &workqueues, list) {
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for_each_pwq(pwq, wq)
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pwq_adjust_max_active(pwq);
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}
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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mutex_unlock(&wq_mutex);
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}
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@ -4352,7 +4355,7 @@ out_unlock:
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* frozen works are transferred to their respective pool worklists.
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*
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* CONTEXT:
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* Grabs and releases wq_mutex, workqueue_lock and pool->lock's.
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* Grabs and releases wq_mutex, pwq_lock and pool->lock's.
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*/
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void thaw_workqueues(void)
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{
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@ -4375,12 +4378,12 @@ void thaw_workqueues(void)
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}
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/* restore max_active and repopulate worklist */
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spin_lock_irq(&workqueue_lock);
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spin_lock_irq(&pwq_lock);
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list_for_each_entry(wq, &workqueues, list) {
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for_each_pwq(pwq, wq)
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pwq_adjust_max_active(pwq);
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}
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spin_unlock_irq(&workqueue_lock);
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spin_unlock_irq(&pwq_lock);
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/* kick workers */
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for_each_pool(pool, pi) {
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