workqueue: Replace pool->attach_mutex with global wq_pool_attach_mutex
To improve workqueue visibility, we want to be able to access workqueue information from worker tasks. The per-pool attach mutex makes that difficult because there's no way of stabilizing task -> worker pool association without knowing the pool first. Worker attach/detach is a slow path and there's no need for different pools to be able to perform them concurrently. This patch replaces the per-pool attach_mutex with global wq_pool_attach_mutex to prepare for visibility improvement changes. Signed-off-by: Tejun Heo <tj@kernel.org>
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Tejun Heo
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e6506eb241
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1258fae73c
@ -66,7 +66,7 @@ enum {
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* be executing on any CPU. The pool behaves as an unbound one.
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*
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* Note that DISASSOCIATED should be flipped only while holding
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* attach_mutex to avoid changing binding state while
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* wq_pool_attach_mutex to avoid changing binding state while
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* worker_attach_to_pool() is in progress.
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*/
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POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
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@ -123,7 +123,7 @@ enum {
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* cpu or grabbing pool->lock is enough for read access. If
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* POOL_DISASSOCIATED is set, it's identical to L.
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*
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* A: pool->attach_mutex protected.
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* A: wq_pool_attach_mutex protected.
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*
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* PL: wq_pool_mutex protected.
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*
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@ -166,7 +166,6 @@ struct worker_pool {
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/* L: hash of busy workers */
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struct worker *manager; /* L: purely informational */
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struct mutex attach_mutex; /* attach/detach exclusion */
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struct list_head workers; /* A: attached workers */
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struct completion *detach_completion; /* all workers detached */
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@ -297,6 +296,7 @@ static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
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static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
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static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
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static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
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static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
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static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
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@ -399,14 +399,14 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
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* @worker: iteration cursor
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* @pool: worker_pool to iterate workers of
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*
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* This must be called with @pool->attach_mutex.
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* This must be called with wq_pool_attach_mutex.
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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_pool_worker(worker, pool) \
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list_for_each_entry((worker), &(pool)->workers, node) \
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if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
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if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
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else
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/**
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@ -1724,7 +1724,7 @@ static struct worker *alloc_worker(int node)
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static void worker_attach_to_pool(struct worker *worker,
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struct worker_pool *pool)
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{
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mutex_lock(&pool->attach_mutex);
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mutex_lock(&wq_pool_attach_mutex);
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/*
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* set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
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@ -1733,16 +1733,16 @@ static void worker_attach_to_pool(struct worker *worker,
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set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
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/*
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* The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
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* stable across this function. See the comments above the
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* flag definition for details.
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* The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
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* stable across this function. See the comments above the flag
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* definition for details.
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*/
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if (pool->flags & POOL_DISASSOCIATED)
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worker->flags |= WORKER_UNBOUND;
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list_add_tail(&worker->node, &pool->workers);
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mutex_unlock(&pool->attach_mutex);
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mutex_unlock(&wq_pool_attach_mutex);
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}
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/**
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@ -1759,11 +1759,11 @@ static void worker_detach_from_pool(struct worker *worker,
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{
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struct completion *detach_completion = NULL;
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mutex_lock(&pool->attach_mutex);
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mutex_lock(&wq_pool_attach_mutex);
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list_del(&worker->node);
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if (list_empty(&pool->workers))
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detach_completion = pool->detach_completion;
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mutex_unlock(&pool->attach_mutex);
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mutex_unlock(&wq_pool_attach_mutex);
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/* clear leftover flags without pool->lock after it is detached */
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worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
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@ -3271,7 +3271,6 @@ static int init_worker_pool(struct worker_pool *pool)
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timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
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mutex_init(&pool->attach_mutex);
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INIT_LIST_HEAD(&pool->workers);
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ida_init(&pool->worker_ida);
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@ -3354,10 +3353,10 @@ static void put_unbound_pool(struct worker_pool *pool)
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WARN_ON(pool->nr_workers || pool->nr_idle);
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spin_unlock_irq(&pool->lock);
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mutex_lock(&pool->attach_mutex);
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mutex_lock(&wq_pool_attach_mutex);
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if (!list_empty(&pool->workers))
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pool->detach_completion = &detach_completion;
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mutex_unlock(&pool->attach_mutex);
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mutex_unlock(&wq_pool_attach_mutex);
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if (pool->detach_completion)
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wait_for_completion(pool->detach_completion);
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@ -4600,7 +4599,7 @@ static void unbind_workers(int cpu)
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struct worker *worker;
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for_each_cpu_worker_pool(pool, cpu) {
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mutex_lock(&pool->attach_mutex);
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mutex_lock(&wq_pool_attach_mutex);
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spin_lock_irq(&pool->lock);
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/*
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@ -4616,7 +4615,7 @@ static void unbind_workers(int cpu)
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pool->flags |= POOL_DISASSOCIATED;
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spin_unlock_irq(&pool->lock);
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mutex_unlock(&pool->attach_mutex);
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mutex_unlock(&wq_pool_attach_mutex);
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/*
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* Call schedule() so that we cross rq->lock and thus can
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@ -4657,7 +4656,7 @@ static void rebind_workers(struct worker_pool *pool)
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{
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struct worker *worker;
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lockdep_assert_held(&pool->attach_mutex);
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lockdep_assert_held(&wq_pool_attach_mutex);
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/*
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* Restore CPU affinity of all workers. As all idle workers should
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@ -4727,7 +4726,7 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
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static cpumask_t cpumask;
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struct worker *worker;
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lockdep_assert_held(&pool->attach_mutex);
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lockdep_assert_held(&wq_pool_attach_mutex);
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/* is @cpu allowed for @pool? */
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if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
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@ -4762,14 +4761,14 @@ int workqueue_online_cpu(unsigned int cpu)
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mutex_lock(&wq_pool_mutex);
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for_each_pool(pool, pi) {
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mutex_lock(&pool->attach_mutex);
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mutex_lock(&wq_pool_attach_mutex);
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if (pool->cpu == cpu)
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rebind_workers(pool);
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else if (pool->cpu < 0)
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restore_unbound_workers_cpumask(pool, cpu);
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mutex_unlock(&pool->attach_mutex);
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mutex_unlock(&wq_pool_attach_mutex);
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}
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/* update NUMA affinity of unbound workqueues */
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