From a0111cf6710bd1b4145ef313d3f4772602af051b Mon Sep 17 00:00:00 2001
From: Lai Jiangshan <laijs@cn.fujitsu.com>
Date: Tue, 19 May 2015 18:03:47 +0800
Subject: [PATCH] workqueue: separate out and refactor the locking of applying
 attrs

Applying attrs requires two locks: get_online_cpus() and wq_pool_mutex,
and this code is duplicated at two places (apply_workqueue_attrs() and
workqueue_set_unbound_cpumask()).  So we separate out this locking
code into apply_wqattrs_[un]lock() and do a minor refactor on
apply_workqueue_attrs().

The apply_wqattrs_[un]lock() will be also used on later patch for
ensuring attrs changes are properly synchronized.

tj: minor updates to comments

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/workqueue.c | 80 ++++++++++++++++++++++++++--------------------
 1 file changed, 46 insertions(+), 34 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 4a9f65b54ee5..72c1adbf7632 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3621,6 +3621,46 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
 	mutex_unlock(&ctx->wq->mutex);
 }
 
+static void apply_wqattrs_lock(void)
+{
+	/* CPUs should stay stable across pwq creations and installations */
+	get_online_cpus();
+	mutex_lock(&wq_pool_mutex);
+}
+
+static void apply_wqattrs_unlock(void)
+{
+	mutex_unlock(&wq_pool_mutex);
+	put_online_cpus();
+}
+
+static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
+					const struct workqueue_attrs *attrs)
+{
+	struct apply_wqattrs_ctx *ctx;
+	int ret = -ENOMEM;
+
+	/* only unbound workqueues can change attributes */
+	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
+		return -EINVAL;
+
+	/* creating multiple pwqs breaks ordering guarantee */
+	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
+		return -EINVAL;
+
+	ctx = apply_wqattrs_prepare(wq, attrs);
+
+	/* the ctx has been prepared successfully, let's commit it */
+	if (ctx) {
+		apply_wqattrs_commit(ctx);
+		ret = 0;
+	}
+
+	apply_wqattrs_cleanup(ctx);
+
+	return ret;
+}
+
 /**
  * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
  * @wq: the target workqueue
@@ -3640,37 +3680,11 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
 int apply_workqueue_attrs(struct workqueue_struct *wq,
 			  const struct workqueue_attrs *attrs)
 {
-	struct apply_wqattrs_ctx *ctx;
-	int ret = -ENOMEM;
+	int ret;
 
-	/* only unbound workqueues can change attributes */
-	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
-		return -EINVAL;
-
-	/* creating multiple pwqs breaks ordering guarantee */
-	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
-		return -EINVAL;
-
-	/*
-	 * CPUs should stay stable across pwq creations and installations.
-	 * Pin CPUs, determine the target cpumask for each node and create
-	 * pwqs accordingly.
-	 */
-	get_online_cpus();
-	mutex_lock(&wq_pool_mutex);
-
-	ctx = apply_wqattrs_prepare(wq, attrs);
-
-	/* the ctx has been prepared successfully, let's commit it */
-	if (ctx) {
-		apply_wqattrs_commit(ctx);
-		ret = 0;
-	}
-
-	mutex_unlock(&wq_pool_mutex);
-	put_online_cpus();
-
-	apply_wqattrs_cleanup(ctx);
+	apply_wqattrs_lock();
+	ret = apply_workqueue_attrs_locked(wq, attrs);
+	apply_wqattrs_unlock();
 
 	return ret;
 }
@@ -4799,10 +4813,9 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
 	if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
 		return -ENOMEM;
 
-	get_online_cpus();
 	cpumask_and(cpumask, cpumask, cpu_possible_mask);
 	if (!cpumask_empty(cpumask)) {
-		mutex_lock(&wq_pool_mutex);
+		apply_wqattrs_lock();
 
 		/* save the old wq_unbound_cpumask. */
 		cpumask_copy(saved_cpumask, wq_unbound_cpumask);
@@ -4815,9 +4828,8 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
 		if (ret < 0)
 			cpumask_copy(wq_unbound_cpumask, saved_cpumask);
 
-		mutex_unlock(&wq_pool_mutex);
+		apply_wqattrs_unlock();
 	}
-	put_online_cpus();
 
 	free_cpumask_var(saved_cpumask);
 	return ret;