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Commit da028469 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: separate iteration role from worker_idr 



worker_idr has the iteration (iterating for attached workers) and
worker ID duties. These two duties don't have to be tied together. We
can separate them and use a list for tracking attached workers and
iteration.

Before this separation, it wasn't possible to add rescuer workers to
worker_idr due to rescuer workers couldn't allocate ID dynamically
because ID-allocation depends on memory-allocation, which rescuer
can't depend on.

After separation, we can easily add the rescuer workers to the list for
iteration without any memory-allocation. It is required when we attach
the rescuer worker to the pool in later patch.

tj: Minor description updates.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 3347fc9f

kernel/workqueue.c

+15 −13
Original line number Diff line number Diff line
@@ -161,7 +161,8 @@ 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 idr		worker_idr;	/* M: worker IDs and iteration */

	struct idr		worker_idr;	/* M: worker IDs */

	struct list_head	workers;	/* M: attached workers */

	struct completion	*detach_completion; /* all workers detached */



	struct workqueue_attrs	*attrs;		/* I: worker attributes */
@@ -363,7 +364,6 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to, 
/**

 * 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 @pool->manager_mutex.
@@ -371,8 +371,8 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to, 
 * 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))		\

#define for_each_pool_worker(worker, pool)				\

	list_for_each_entry((worker), &(pool)->workers, node)		\

		if (({ lockdep_assert_held(&pool->manager_mutex); false; })) { } \

		else
@@ -1674,6 +1674,7 @@ static struct worker *alloc_worker(void) 
	if (worker) {

		INIT_LIST_HEAD(&worker->entry);

		INIT_LIST_HEAD(&worker->scheduled);

		INIT_LIST_HEAD(&worker->node);

		/* on creation a worker is in !idle && prep state */

		worker->flags = WORKER_PREP;

	}
@@ -1696,7 +1697,8 @@ static void worker_detach_from_pool(struct worker *worker, 


	mutex_lock(&pool->manager_mutex);

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

	if (idr_is_empty(&pool->worker_idr))

	list_del(&worker->node);

	if (list_empty(&pool->workers))

		detach_completion = pool->detach_completion;

	mutex_unlock(&pool->manager_mutex);
@@ -1772,6 +1774,8 @@ static struct worker *create_worker(struct worker_pool *pool) 


	/* successful, commit the pointer to idr */

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

	/* successful, attach the worker to the pool */

	list_add_tail(&worker->node, &pool->workers);



	return worker;
@@ -3483,6 +3487,7 @@ static int init_worker_pool(struct worker_pool *pool) 
	mutex_init(&pool->manager_arb);

	mutex_init(&pool->manager_mutex);

	idr_init(&pool->worker_idr);

	INIT_LIST_HEAD(&pool->workers);



	INIT_HLIST_NODE(&pool->hash_node);

	pool->refcnt = 1;
@@ -3548,7 +3553,7 @@ static void put_unbound_pool(struct worker_pool *pool) 
	spin_unlock_irq(&pool->lock);



	mutex_lock(&pool->manager_mutex);

	if (!idr_is_empty(&pool->worker_idr))

	if (!list_empty(&pool->workers))

		pool->detach_completion = &detach_completion;

	mutex_unlock(&pool->manager_mutex);
@@ -4533,7 +4538,6 @@ static void wq_unbind_fn(struct work_struct *work) 
	int cpu = smp_processor_id();

	struct worker_pool *pool;

	struct worker *worker;

	int wi;



	for_each_cpu_worker_pool(pool, cpu) {

		WARN_ON_ONCE(cpu != smp_processor_id());
@@ -4548,7 +4552,7 @@ static void wq_unbind_fn(struct work_struct *work) 
		 * before the last CPU down must be on the cpu.  After

		 * this, they may become diasporas.

		 */

		for_each_pool_worker(worker, wi, pool)

		for_each_pool_worker(worker, pool)

			worker->flags |= WORKER_UNBOUND;



		pool->flags |= POOL_DISASSOCIATED;
@@ -4594,7 +4598,6 @@ static void wq_unbind_fn(struct work_struct *work) 
static void rebind_workers(struct worker_pool *pool)

{

	struct worker *worker;

	int wi;



	lockdep_assert_held(&pool->manager_mutex);
@@ -4605,13 +4608,13 @@ static void rebind_workers(struct worker_pool *pool) 
	 * of all workers first and then clear UNBOUND.  As we're called

	 * from CPU_ONLINE, the following shouldn't fail.

	 */

	for_each_pool_worker(worker, wi, pool)

	for_each_pool_worker(worker, pool)

		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,

						  pool->attrs->cpumask) < 0);



	spin_lock_irq(&pool->lock);



	for_each_pool_worker(worker, wi, pool) {

	for_each_pool_worker(worker, pool) {

		unsigned int worker_flags = worker->flags;



		/*
@@ -4663,7 +4666,6 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu) 
{

	static cpumask_t cpumask;

	struct worker *worker;

	int wi;



	lockdep_assert_held(&pool->manager_mutex);
@@ -4677,7 +4679,7 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu) 
		return;



	/* as we're called from CPU_ONLINE, the following shouldn't fail */

	for_each_pool_worker(worker, wi, pool)

	for_each_pool_worker(worker, pool)

		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,

						  pool->attrs->cpumask) < 0);

}

kernel/workqueue_internal.h

+2 −0
Original line number Diff line number Diff line
@@ -37,6 +37,8 @@ struct worker { 
	struct task_struct	*task;		/* I: worker task */

	struct worker_pool	*pool;		/* I: the associated pool */

						/* L: for rescuers */

	struct list_head	node;		/* M: anchored at pool->workers */

						/* M: runs through worker->node */



	unsigned long		last_active;	/* L: last active timestamp */

	unsigned int		flags;		/* X: flags */