[PATCH 05/10 V2] workqueue: separate iteration role from worker_idr

[Lai Jiangshan <laijs@cn.fujitsu.com>]

worker_idr has the iteration(iterating for attached workers) and worker ID
duties. These two duties are not necessary tied together. We can separate
them and use a list for tracking attached workers and iteration

After separation, we can add the rescuer workers to the list for iteration
in future. worker_idr can't add rescuer workers due to rescuer workers
can't allocate id from worker_idr.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 kernel/workqueue.c          |   39 +++++++++++++--------------------------
 kernel/workqueue_internal.h |    1 +
 2 files changed, 14 insertions(+), 26 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 95695c3..b6cf4d9 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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 */
@@ -361,22 +362,6 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
 		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 @pool->manager_mutex.
- *
- * 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 (({ lockdep_assert_held(&pool->manager_mutex); false; })) { } \
-		else
-
-/**
  * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
  * @pwq: iteration cursor
  * @wq: the target workqueue
@@ -1674,6 +1659,7 @@ 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 +1682,8 @@ 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 +1759,8 @@ 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;
 
@@ -3481,6 +3470,7 @@ 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;
@@ -3545,7 +3535,7 @@ 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);
 
@@ -4530,7 +4520,6 @@ 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());
@@ -4545,7 +4534,7 @@ 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)
+		list_for_each_entry(worker, &pool->workers, node)
 			worker->flags |= WORKER_UNBOUND;
 
 		pool->flags |= POOL_DISASSOCIATED;
@@ -4591,7 +4580,6 @@ 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);
 
@@ -4602,13 +4590,13 @@ 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)
+	list_for_each_entry(worker, &pool->workers, node)
 		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) {
+	list_for_each_entry(worker, &pool->workers, node) {
 		unsigned int worker_flags = worker->flags;
 
 		/*
@@ -4660,7 +4648,6 @@ 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);
 
@@ -4674,7 +4661,7 @@ 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)
+	list_for_each_entry(worker, &pool->workers, node)
 		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
 						  pool->attrs->cpumask) < 0);
 }
diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
index 7e2204d..c44abc3 100644
--- a/kernel/workqueue_internal.h
+++ b/kernel/workqueue_internal.h
@@ -37,6 +37,7 @@ 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: attached to the pool */
 
 	unsigned long		last_active;	/* L: last active timestamp */
 	unsigned int		flags;		/* X: flags */
-- 
1.7.4.4