workqueue: break init_and_link_pwq() into two functions and introduce alloc_unbound_pwq()

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@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 170226a..c8d047b 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3626,13 +3626,10 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
        spin_unlock_irq(&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;
@@ -3642,8 +3639,15 @@ 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->mutex);
+/* 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->mutex);
 
        /*
         * Set the matching work_color.  This is synchronized with
@@ -3658,14 +3662,29 @@ 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;
+
+       lockdep_assert_held(&wq_pool_mutex);
+
+       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;
        }
 
-       mutex_unlock(&wq->mutex);
+       init_pwq(pwq, wq, pool);
+       return pwq;
 }
 
 /**
@@ -3686,9 +3705,8 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
                          const struct workqueue_attrs *attrs)
 {
        struct workqueue_attrs *new_attrs;
-       struct pool_workqueue *pwq = NULL, *last_pwq;
-       struct worker_pool *pool;
-       int ret;
+       struct pool_workqueue *pwq, *last_pwq;
+       int node, ret;
 
        /* only unbound workqueues can change attributes */
        if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
@@ -3707,22 +3725,21 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
        cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
 
        mutex_lock(&wq_pool_mutex);
-
-       pwq = kmem_cache_zalloc(pwq_cache, GFP_KERNEL);
-       if (!pwq) {
-               mutex_unlock(&wq_pool_mutex);
+       pwq = alloc_unbound_pwq(wq, new_attrs);
+       mutex_unlock(&wq_pool_mutex);
+       if (!pwq)
                goto enomem;
-       }
 
-       pool = get_unbound_pool(new_attrs);
-       if (!pool) {
-               mutex_unlock(&wq_pool_mutex);
-               goto enomem;
-       }
+       mutex_lock(&wq->mutex);
 
-       mutex_unlock(&wq_pool_mutex);
+       link_pwq(pwq, &last_pwq);
+
+       copy_workqueue_attrs(wq->unbound_attrs, new_attrs);
+       for_each_node(node)
+               rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
+
+       mutex_unlock(&wq->mutex);
 
-       init_and_link_pwq(pwq, wq, pool, &last_pwq);
        if (last_pwq) {
                spin_lock_irq(&last_pwq->pool->lock);
                put_pwq(last_pwq);
@@ -3736,7 +3753,6 @@ out_free:
        return ret;
 
 enomem:
-       kmem_cache_free(pwq_cache, pwq);
        ret = -ENOMEM;
        goto out_free;
 }
@@ -3757,7 +3773,11 @@ 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->mutex);
+                       link_pwq(pwq, NULL);
+                       mutex_unlock(&wq->mutex);
                }
                return 0;
        } else {