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Commit 822d8405 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: convert worker_pool->worker_ida to idr and implement for_each_pool_worker() 



Make worker_ida an idr - worker_idr and use it to implement
for_each_pool_worker() which will be used to simplify worker rebinding
on CPU_ONLINE.

pool->worker_idr is protected by both pool->manager_mutex and
pool->lock so that it can be iterated while holding either lock.

* create_worker() allocates ID without installing worker pointer and
  installs the pointer later using idr_replace().  This is because
  worker ID is needed when creating the actual task to name it and the
  new worker shouldn't be visible to iterations before fully
  initialized.

* In destroy_worker(), ID removal is moved before kthread_stop().
  This is again to guarantee that only fully working workers are
  visible to for_each_pool_worker().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
parent 14a40ffc

kernel/workqueue.c

+51 −12
Original line number Diff line number Diff line
@@ -119,6 +119,9 @@ enum { 
 *

 * F: wq->flush_mutex protected.

 *

 * MG: pool->manager_mutex and pool->lock protected.  Writes require both

 *     locks.  Reads can happen under either lock.

 *

 * WQ: wq_mutex protected.

 *

 * WR: wq_mutex protected for writes.  Sched-RCU protected for reads.
@@ -156,7 +159,7 @@ struct worker_pool { 
	/* see manage_workers() for details on the two manager mutexes */

	struct mutex		manager_arb;	/* manager arbitration */

	struct mutex		manager_mutex;	/* manager exclusion */

	struct ida		worker_ida;	/* L: for worker IDs */

	struct idr		worker_idr;	/* MG: worker IDs and iteration */



	struct workqueue_attrs	*attrs;		/* I: worker attributes */

	struct hlist_node	hash_node;	/* WQ: unbound_pool_hash node */
@@ -299,6 +302,15 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to, 
			   lockdep_is_held(&pwq_lock),			\

			   "sched RCU or pwq_lock should be held")



#ifdef CONFIG_LOCKDEP

#define assert_manager_or_pool_lock(pool)				\

	WARN_ONCE(!lockdep_is_held(&(pool)->manager_mutex) &&		\

		  !lockdep_is_held(&(pool)->lock),			\

		  "pool->manager_mutex or ->lock should be held")

#else

#define assert_manager_or_pool_lock(pool)	do { } while (0)

#endif



#define for_each_cpu_worker_pool(pool, cpu)				\

	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\

	     (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
@@ -324,6 +336,22 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to, 
		if (({ assert_rcu_or_wq_mutex(); false; })) { }		\

		else



/**

 * for_each_pool_worker - iterate through all workers of a worker_pool

 * @worker: iteration cursor

 * @wi: integer used for iteration

 * @pool: worker_pool to iterate workers of

 *

 * This must be called with either @pool->manager_mutex or ->lock held.

 *

 * The if/else clause exists only for the lockdep assertion and can be

 * ignored.

 */

#define for_each_pool_worker(worker, wi, pool)				\

	idr_for_each_entry(&(pool)->worker_idr, (worker), (wi))		\

		if (({ assert_manager_or_pool_lock((pool)); false; })) { } \

		else



/**

 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue

 * @pwq: iteration cursor
@@ -1723,14 +1751,19 @@ static struct worker *create_worker(struct worker_pool *pool) 


	lockdep_assert_held(&pool->manager_mutex);



	/*

	 * ID is needed to determine kthread name.  Allocate ID first

	 * without installing the pointer.

	 */

	idr_preload(GFP_KERNEL);

	spin_lock_irq(&pool->lock);

	while (ida_get_new(&pool->worker_ida, &id)) {



	id = idr_alloc(&pool->worker_idr, NULL, 0, 0, GFP_NOWAIT);



	spin_unlock_irq(&pool->lock);

		if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL))

	idr_preload_end();

	if (id < 0)

		goto fail;

		spin_lock_irq(&pool->lock);

	}

	spin_unlock_irq(&pool->lock);



	worker = alloc_worker();

	if (!worker)
@@ -1768,11 +1801,17 @@ static struct worker *create_worker(struct worker_pool *pool) 
	if (pool->flags & POOL_DISASSOCIATED)

		worker->flags |= WORKER_UNBOUND;



	/* successful, commit the pointer to idr */

	spin_lock_irq(&pool->lock);

	idr_replace(&pool->worker_idr, worker, worker->id);

	spin_unlock_irq(&pool->lock);



	return worker;



fail:

	if (id >= 0) {

		spin_lock_irq(&pool->lock);

		ida_remove(&pool->worker_ida, id);

		idr_remove(&pool->worker_idr, id);

		spin_unlock_irq(&pool->lock);

	}

	kfree(worker);
@@ -1832,7 +1871,6 @@ static int create_and_start_worker(struct worker_pool *pool) 
static void destroy_worker(struct worker *worker)

{

	struct worker_pool *pool = worker->pool;

	int id = worker->id;



	lockdep_assert_held(&pool->manager_mutex);

	lockdep_assert_held(&pool->lock);
@@ -1850,13 +1888,14 @@ static void destroy_worker(struct worker *worker) 
	list_del_init(&worker->entry);

	worker->flags |= WORKER_DIE;



	idr_remove(&pool->worker_idr, worker->id);



	spin_unlock_irq(&pool->lock);



	kthread_stop(worker->task);

	kfree(worker);



	spin_lock_irq(&pool->lock);

	ida_remove(&pool->worker_ida, id);

}



static void idle_worker_timeout(unsigned long __pool)
@@ -3482,7 +3521,7 @@ static int init_worker_pool(struct worker_pool *pool) 


	mutex_init(&pool->manager_arb);

	mutex_init(&pool->manager_mutex);

	ida_init(&pool->worker_ida);

	idr_init(&pool->worker_idr);



	INIT_HLIST_NODE(&pool->hash_node);

	pool->refcnt = 1;
@@ -3498,7 +3537,7 @@ static void rcu_free_pool(struct rcu_head *rcu) 
{

	struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);



	ida_destroy(&pool->worker_ida);

	idr_destroy(&pool->worker_idr);

	free_workqueue_attrs(pool->attrs);

	kfree(pool);

}