[PATCH 08/10] workqueue: break init_and_link_pwq() into two functions and introduce alloc_unbound_pwq()

[Tejun Heo]

Break init_and_link_pwq() into init_pwq() and link_pwq() and move
unbound-workqueue specific handling into apply_workqueue_attrs().
Also, factor out unbound pool and pool_workqueue allocation into
alloc_unbound_pwq().

This reorganization is to prepare for NUMA affinity and doesn't
introduce any functional changes.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
 kernel/workqueue.c | 75 +++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 52 insertions(+), 23 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 3f820a5..bbbfc92 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3647,13 +3647,10 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
 	spin_unlock(&pwq->pool->lock);
 }
 
-static void init_and_link_pwq(struct pool_workqueue *pwq,
-			      struct workqueue_struct *wq,
-			      struct worker_pool *pool,
-			      struct pool_workqueue **p_last_pwq)
+/* initialize newly zalloced @pwq which is associated with @wq and @pool */
+static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
+		     struct worker_pool *pool)
 {
-	int node;
-
 	BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
 
 	pwq->pool = pool;
@@ -3663,9 +3660,16 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
 	INIT_LIST_HEAD(&pwq->delayed_works);
 	INIT_LIST_HEAD(&pwq->mayday_node);
 	INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
+}
 
-	mutex_lock(&wq->flush_mutex);
-	spin_lock_irq(&pwq_lock);
+/* sync @pwq with the current state of its associated wq and link it */
+static void link_pwq(struct pool_workqueue *pwq,
+		     struct pool_workqueue **p_last_pwq)
+{
+	struct workqueue_struct *wq = pwq->wq;
+
+	lockdep_assert_held(&wq->flush_mutex);
+	lockdep_assert_held(&pwq_lock);
 
 	/*
 	 * Set the matching work_color.  This is synchronized with
@@ -3680,15 +3684,27 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
 
 	/* link in @pwq */
 	list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
+}
 
-	if (wq->flags & WQ_UNBOUND) {
-		copy_workqueue_attrs(wq->unbound_attrs, pool->attrs);
-		for_each_node(node)
-			rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
+/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
+static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
+					const struct workqueue_attrs *attrs)
+{
+	struct worker_pool *pool;
+	struct pool_workqueue *pwq;
+
+	pool = get_unbound_pool(attrs);
+	if (!pool)
+		return NULL;
+
+	pwq = kmem_cache_zalloc(pwq_cache, GFP_KERNEL);
+	if (!pwq) {
+		put_unbound_pool(pool);
+		return NULL;
 	}
 
-	spin_unlock_irq(&pwq_lock);
-	mutex_unlock(&wq->flush_mutex);
+	init_pwq(pwq, wq, pool);
+	return pwq;
 }
 
 /**
@@ -3709,7 +3725,7 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
 			  const struct workqueue_attrs *attrs)
 {
 	struct pool_workqueue *pwq, *last_pwq;
-	struct worker_pool *pool;
+	int node;
 
 	/* only unbound workqueues can change attributes */
 	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
@@ -3719,17 +3735,22 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
 	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
 		return -EINVAL;
 
-	pwq = kmem_cache_zalloc(pwq_cache, GFP_KERNEL);
+	pwq = alloc_unbound_pwq(wq, attrs);
 	if (!pwq)
 		return -ENOMEM;
 
-	pool = get_unbound_pool(attrs);
-	if (!pool) {
-		kmem_cache_free(pwq_cache, pwq);
-		return -ENOMEM;
-	}
+	mutex_lock(&wq->flush_mutex);
+	spin_lock_irq(&pwq_lock);
+
+	link_pwq(pwq, &last_pwq);
+
+	copy_workqueue_attrs(wq->unbound_attrs, pwq->pool->attrs);
+	for_each_node(node)
+		rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
+
+	spin_unlock_irq(&pwq_lock);
+	mutex_unlock(&wq->flush_mutex);
 
-	init_and_link_pwq(pwq, wq, pool, &last_pwq);
 	if (last_pwq) {
 		spin_lock_irq(&last_pwq->pool->lock);
 		put_pwq(last_pwq);
@@ -3755,7 +3776,15 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
 			struct worker_pool *cpu_pools =
 				per_cpu(cpu_worker_pools, cpu);
 
-			init_and_link_pwq(pwq, wq, &cpu_pools[highpri], NULL);
+			init_pwq(pwq, wq, &cpu_pools[highpri]);
+
+			mutex_lock(&wq->flush_mutex);
+			spin_lock_irq(&pwq_lock);
+
+			link_pwq(pwq, NULL);
+
+			spin_unlock_irq(&pwq_lock);
+			mutex_unlock(&wq->flush_mutex);
 		}
 		return 0;
 	} else {
-- 
1.8.1.4

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