Linux-libre 4.2-gnu

1 files changed, 324 insertions, 169 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 586ad9130..a413acb59 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -127,6 +127,11 @@ enum {
  *
  * PR: wq_pool_mutex protected for writes.  Sched-RCU protected for reads.
  *
+ * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
+ *
+ * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
+ *      sched-RCU for reads.
+ *
  * WQ: wq->mutex protected.
  *
  * WR: wq->mutex protected for writes.  Sched-RCU protected for reads.
@@ -247,8 +252,8 @@ struct workqueue_struct {
 	int			nr_drainers;	/* WQ: drain in progress */
 	int			saved_max_active; /* WQ: saved pwq max_active */
 
-	struct workqueue_attrs	*unbound_attrs;	/* WQ: only for unbound wqs */
-	struct pool_workqueue	*dfl_pwq;	/* WQ: only for unbound wqs */
+	struct workqueue_attrs	*unbound_attrs;	/* PW: only for unbound wqs */
+	struct pool_workqueue	*dfl_pwq;	/* PW: only for unbound wqs */
 
 #ifdef CONFIG_SYSFS
 	struct wq_device	*wq_dev;	/* I: for sysfs interface */
@@ -268,7 +273,7 @@ struct workqueue_struct {
 	/* hot fields used during command issue, aligned to cacheline */
 	unsigned int		flags ____cacheline_aligned; /* WQ: WQ_* flags */
 	struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
-	struct pool_workqueue __rcu *numa_pwq_tbl[]; /* FR: unbound pwqs indexed by node */
+	struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
 };
 
 static struct kmem_cache *pwq_cache;
@@ -280,12 +285,7 @@ static bool wq_disable_numa;
 module_param_named(disable_numa, wq_disable_numa, bool, 0444);
 
 /* see the comment above the definition of WQ_POWER_EFFICIENT */
-#ifdef CONFIG_WQ_POWER_EFFICIENT_DEFAULT
-static bool wq_power_efficient = true;
-#else
-static bool wq_power_efficient;
-#endif
-
+static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
 
 static bool wq_numa_enabled;		/* unbound NUMA affinity enabled */
@@ -299,6 +299,8 @@ static DEFINE_SPINLOCK(wq_mayday_lock);	/* protects wq->maydays list */
 static LIST_HEAD(workqueues);		/* PR: list of all workqueues */
 static bool workqueue_freezing;		/* PL: have wqs started freezing? */
 
+static cpumask_var_t wq_unbound_cpumask; /* PL: low level cpumask for all unbound wqs */
+
 /* the per-cpu worker pools */
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
 				     cpu_worker_pools);
@@ -330,8 +332,6 @@ struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
 
 static int worker_thread(void *__worker);
-static void copy_workqueue_attrs(struct workqueue_attrs *to,
-				 const struct workqueue_attrs *from);
 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
 
 #define CREATE_TRACE_POINTS
@@ -347,6 +347,12 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
 			   lockdep_is_held(&wq->mutex),			\
 			   "sched RCU or wq->mutex should be held")
 
+#define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
+	rcu_lockdep_assert(rcu_read_lock_sched_held() ||		\
+			   lockdep_is_held(&wq->mutex) ||		\
+			   lockdep_is_held(&wq_pool_mutex),		\
+			   "sched RCU, wq->mutex or wq_pool_mutex should be held")
+
 #define for_each_cpu_worker_pool(pool, cpu)				\
 	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\
 	     (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
@@ -551,7 +557,8 @@ static int worker_pool_assign_id(struct worker_pool *pool)
  * @wq: the target workqueue
  * @node: the node ID
  *
- * This must be called either with pwq_lock held or sched RCU read locked.
+ * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
+ * read locked.
  * If the pwq needs to be used beyond the locking in effect, the caller is
  * responsible for guaranteeing that the pwq stays online.
  *
@@ -560,7 +567,7 @@ static int worker_pool_assign_id(struct worker_pool *pool)
 static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
 						  int node)
 {
-	assert_rcu_or_wq_mutex(wq);
+	assert_rcu_or_wq_mutex_or_pool_mutex(wq);
 	return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
 }
 
@@ -976,7 +983,7 @@ static struct worker *find_worker_executing_work(struct worker_pool *pool,
  * move_linked_works - move linked works to a list
  * @work: start of series of works to be scheduled
  * @head: target list to append @work to
- * @nextp: out paramter for nested worklist walking
+ * @nextp: out parameter for nested worklist walking
  *
  * Schedule linked works starting from @work to @head.  Work series to
  * be scheduled starts at @work and includes any consecutive work with
@@ -2607,7 +2614,7 @@ void flush_workqueue(struct workqueue_struct *wq)
 out_unlock:
 	mutex_unlock(&wq->mutex);
 }
-EXPORT_SYMBOL_GPL(flush_workqueue);
+EXPORT_SYMBOL(flush_workqueue);
 
 /**
  * drain_workqueue - drain a workqueue
@@ -2616,7 +2623,7 @@ EXPORT_SYMBOL_GPL(flush_workqueue);
  * Wait until the workqueue becomes empty.  While draining is in progress,
  * only chain queueing is allowed.  IOW, only currently pending or running
  * work items on @wq can queue further work items on it.  @wq is flushed
- * repeatedly until it becomes empty.  The number of flushing is detemined
+ * repeatedly until it becomes empty.  The number of flushing is determined
  * by the depth of chaining and should be relatively short.  Whine if it
  * takes too long.
  */
@@ -2947,36 +2954,6 @@ int schedule_on_each_cpu(work_func_t func)
 }
 
 /**
- * flush_scheduled_work - ensure that any scheduled work has run to completion.
- *
- * Forces execution of the kernel-global workqueue and blocks until its
- * completion.
- *
- * Think twice before calling this function!  It's very easy to get into
- * trouble if you don't take great care.  Either of the following situations
- * will lead to deadlock:
- *
- *	One of the work items currently on the workqueue needs to acquire
- *	a lock held by your code or its caller.
- *
- *	Your code is running in the context of a work routine.
- *
- * They will be detected by lockdep when they occur, but the first might not
- * occur very often.  It depends on what work items are on the workqueue and
- * what locks they need, which you have no control over.
- *
- * In most situations flushing the entire workqueue is overkill; you merely
- * need to know that a particular work item isn't queued and isn't running.
- * In such cases you should use cancel_delayed_work_sync() or
- * cancel_work_sync() instead.
- */
-void flush_scheduled_work(void)
-{
-	flush_workqueue(system_wq);
-}
-EXPORT_SYMBOL(flush_scheduled_work);
-
-/**
  * execute_in_process_context - reliably execute the routine with user context
  * @fn:		the function to execute
  * @ew:		guaranteed storage for the execute work structure (must
@@ -3081,7 +3058,7 @@ static bool wqattrs_equal(const struct workqueue_attrs *a,
  * init_worker_pool - initialize a newly zalloc'd worker_pool
  * @pool: worker_pool to initialize
  *
- * Initiailize a newly zalloc'd @pool.  It also allocates @pool->attrs.
+ * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
  *
  * Return: 0 on success, -errno on failure.  Even on failure, all fields
  * inside @pool proper are initialized and put_unbound_pool() can be called
@@ -3425,20 +3402,9 @@ static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
 	return pwq;
 }
 
-/* undo alloc_unbound_pwq(), used only in the error path */
-static void free_unbound_pwq(struct pool_workqueue *pwq)
-{
-	lockdep_assert_held(&wq_pool_mutex);
-
-	if (pwq) {
-		put_unbound_pool(pwq->pool);
-		kmem_cache_free(pwq_cache, pwq);
-	}
-}
-
 /**
- * wq_calc_node_mask - calculate a wq_attrs' cpumask for the specified node
- * @attrs: the wq_attrs of interest
+ * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
+ * @attrs: the wq_attrs of the default pwq of the target workqueue
  * @node: the target NUMA node
  * @cpu_going_down: if >= 0, the CPU to consider as offline
  * @cpumask: outarg, the resulting cpumask
@@ -3488,6 +3454,7 @@ static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
 {
 	struct pool_workqueue *old_pwq;
 
+	lockdep_assert_held(&wq_pool_mutex);
 	lockdep_assert_held(&wq->mutex);
 
 	/* link_pwq() can handle duplicate calls */
@@ -3498,46 +3465,59 @@ static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
 	return old_pwq;
 }
 
-/**
- * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
- * @wq: the target workqueue
- * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
- *
- * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
- * machines, this function maps a separate pwq to each NUMA node with
- * possibles CPUs in @attrs->cpumask so that work items are affine to the
- * NUMA node it was issued on.  Older pwqs are released as in-flight work
- * items finish.  Note that a work item which repeatedly requeues itself
- * back-to-back will stay on its current pwq.
- *
- * Performs GFP_KERNEL allocations.
- *
- * Return: 0 on success and -errno on failure.
- */
-int apply_workqueue_attrs(struct workqueue_struct *wq,
-			  const struct workqueue_attrs *attrs)
+/* context to store the prepared attrs & pwqs before applying */
+struct apply_wqattrs_ctx {
+	struct workqueue_struct	*wq;		/* target workqueue */
+	struct workqueue_attrs	*attrs;		/* attrs to apply */
+	struct list_head	list;		/* queued for batching commit */
+	struct pool_workqueue	*dfl_pwq;
+	struct pool_workqueue	*pwq_tbl[];
+};
+
+/* free the resources after success or abort */
+static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
+{
+	if (ctx) {
+		int node;
+
+		for_each_node(node)
+			put_pwq_unlocked(ctx->pwq_tbl[node]);
+		put_pwq_unlocked(ctx->dfl_pwq);
+
+		free_workqueue_attrs(ctx->attrs);
+
+		kfree(ctx);
+	}
+}
+
+/* allocate the attrs and pwqs for later installation */
+static struct apply_wqattrs_ctx *
+apply_wqattrs_prepare(struct workqueue_struct *wq,
+		      const struct workqueue_attrs *attrs)
 {
+	struct apply_wqattrs_ctx *ctx;
 	struct workqueue_attrs *new_attrs, *tmp_attrs;
-	struct pool_workqueue **pwq_tbl, *dfl_pwq;
-	int node, ret;
+	int node;
 
-	/* only unbound workqueues can change attributes */
-	if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
-		return -EINVAL;
+	lockdep_assert_held(&wq_pool_mutex);
 
-	/* creating multiple pwqs breaks ordering guarantee */
-	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
-		return -EINVAL;
+	ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
+		      GFP_KERNEL);
 
-	pwq_tbl = kzalloc(nr_node_ids * sizeof(pwq_tbl[0]), GFP_KERNEL);
 	new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
 	tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
-	if (!pwq_tbl || !new_attrs || !tmp_attrs)
-		goto enomem;
+	if (!ctx || !new_attrs || !tmp_attrs)
+		goto out_free;
 
-	/* make a copy of @attrs and sanitize it */
+	/*
+	 * Calculate the attrs of the default pwq.
+	 * If the user configured cpumask doesn't overlap with the
+	 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
+	 */
 	copy_workqueue_attrs(new_attrs, attrs);
-	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
+	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
+	if (unlikely(cpumask_empty(new_attrs->cpumask)))
+		cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
 
 	/*
 	 * We may create multiple pwqs with differing cpumasks.  Make a
@@ -3547,75 +3527,129 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
 	copy_workqueue_attrs(tmp_attrs, new_attrs);
 
 	/*
-	 * 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);
-
-	/*
 	 * If something goes wrong during CPU up/down, we'll fall back to
 	 * the default pwq covering whole @attrs->cpumask.  Always create
 	 * it even if we don't use it immediately.
 	 */
-	dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
-	if (!dfl_pwq)
-		goto enomem_pwq;
+	ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
+	if (!ctx->dfl_pwq)
+		goto out_free;
 
 	for_each_node(node) {
-		if (wq_calc_node_cpumask(attrs, node, -1, tmp_attrs->cpumask)) {
-			pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
-			if (!pwq_tbl[node])
-				goto enomem_pwq;
+		if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
+			ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
+			if (!ctx->pwq_tbl[node])
+				goto out_free;
 		} else {
-			dfl_pwq->refcnt++;
-			pwq_tbl[node] = dfl_pwq;
+			ctx->dfl_pwq->refcnt++;
+			ctx->pwq_tbl[node] = ctx->dfl_pwq;
 		}
 	}
 
-	mutex_unlock(&wq_pool_mutex);
+	/* save the user configured attrs and sanitize it. */
+	copy_workqueue_attrs(new_attrs, attrs);
+	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
+	ctx->attrs = new_attrs;
+
+	ctx->wq = wq;
+	free_workqueue_attrs(tmp_attrs);
+	return ctx;
+
+out_free:
+	free_workqueue_attrs(tmp_attrs);
+	free_workqueue_attrs(new_attrs);
+	apply_wqattrs_cleanup(ctx);
+	return NULL;
+}
+
+/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
+static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
+{
+	int node;
 
 	/* all pwqs have been created successfully, let's install'em */
-	mutex_lock(&wq->mutex);
+	mutex_lock(&ctx->wq->mutex);
 
-	copy_workqueue_attrs(wq->unbound_attrs, new_attrs);
+	copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
 
 	/* save the previous pwq and install the new one */
 	for_each_node(node)
-		pwq_tbl[node] = numa_pwq_tbl_install(wq, node, pwq_tbl[node]);
+		ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
+							  ctx->pwq_tbl[node]);
 
 	/* @dfl_pwq might not have been used, ensure it's linked */
-	link_pwq(dfl_pwq);
-	swap(wq->dfl_pwq, dfl_pwq);
+	link_pwq(ctx->dfl_pwq);
+	swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
 
-	mutex_unlock(&wq->mutex);
+	mutex_unlock(&ctx->wq->mutex);
+}
 
-	/* put the old pwqs */
-	for_each_node(node)
-		put_pwq_unlocked(pwq_tbl[node]);
-	put_pwq_unlocked(dfl_pwq);
+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();
-	ret = 0;
-	/* fall through */
-out_free:
-	free_workqueue_attrs(tmp_attrs);
-	free_workqueue_attrs(new_attrs);
-	kfree(pwq_tbl);
+}
+
+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;
+}
 
-enomem_pwq:
-	free_unbound_pwq(dfl_pwq);
-	for_each_node(node)
-		if (pwq_tbl && pwq_tbl[node] != dfl_pwq)
-			free_unbound_pwq(pwq_tbl[node]);
-	mutex_unlock(&wq_pool_mutex);
-	put_online_cpus();
-enomem:
-	ret = -ENOMEM;
-	goto out_free;
+/**
+ * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
+ * @wq: the target workqueue
+ * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
+ *
+ * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
+ * machines, this function maps a separate pwq to each NUMA node with
+ * possibles CPUs in @attrs->cpumask so that work items are affine to the
+ * NUMA node it was issued on.  Older pwqs are released as in-flight work
+ * items finish.  Note that a work item which repeatedly requeues itself
+ * back-to-back will stay on its current pwq.
+ *
+ * Performs GFP_KERNEL allocations.
+ *
+ * Return: 0 on success and -errno on failure.
+ */
+int apply_workqueue_attrs(struct workqueue_struct *wq,
+			  const struct workqueue_attrs *attrs)
+{
+	int ret;
+
+	apply_wqattrs_lock();
+	ret = apply_workqueue_attrs_locked(wq, attrs);
+	apply_wqattrs_unlock();
+
+	return ret;
 }
 
 /**
@@ -3651,7 +3685,8 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
 
 	lockdep_assert_held(&wq_pool_mutex);
 
-	if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND))
+	if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
+	    wq->unbound_attrs->no_numa)
 		return;
 
 	/*
@@ -3662,48 +3697,37 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
 	target_attrs = wq_update_unbound_numa_attrs_buf;
 	cpumask = target_attrs->cpumask;
 
-	mutex_lock(&wq->mutex);
-	if (wq->unbound_attrs->no_numa)
-		goto out_unlock;
-
 	copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
 	pwq = unbound_pwq_by_node(wq, node);
 
 	/*
 	 * Let's determine what needs to be done.  If the target cpumask is
-	 * different from wq's, we need to compare it to @pwq's and create
-	 * a new one if they don't match.  If the target cpumask equals
-	 * wq's, the default pwq should be used.
+	 * different from the default pwq's, we need to compare it to @pwq's
+	 * and create a new one if they don't match.  If the target cpumask
+	 * equals the default pwq's, the default pwq should be used.
 	 */
-	if (wq_calc_node_cpumask(wq->unbound_attrs, node, cpu_off, cpumask)) {
+	if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
 		if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
-			goto out_unlock;
+			return;
 	} else {
 		goto use_dfl_pwq;
 	}
 
-	mutex_unlock(&wq->mutex);
-
 	/* create a new pwq */
 	pwq = alloc_unbound_pwq(wq, target_attrs);
 	if (!pwq) {
 		pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
 			wq->name);
-		mutex_lock(&wq->mutex);
 		goto use_dfl_pwq;
 	}
 
-	/*
-	 * Install the new pwq.  As this function is called only from CPU
-	 * hotplug callbacks and applying a new attrs is wrapped with
-	 * get/put_online_cpus(), @wq->unbound_attrs couldn't have changed
-	 * inbetween.
-	 */
+	/* Install the new pwq. */
 	mutex_lock(&wq->mutex);
 	old_pwq = numa_pwq_tbl_install(wq, node, pwq);
 	goto out_unlock;
 
 use_dfl_pwq:
+	mutex_lock(&wq->mutex);
 	spin_lock_irq(&wq->dfl_pwq->pool->lock);
 	get_pwq(wq->dfl_pwq);
 	spin_unlock_irq(&wq->dfl_pwq->pool->lock);
@@ -4385,7 +4409,7 @@ static void rebind_workers(struct worker_pool *pool)
 	/*
 	 * Restore CPU affinity of all workers.  As all idle workers should
 	 * be on the run-queue of the associated CPU before any local
-	 * wake-ups for concurrency management happen, restore CPU affinty
+	 * wake-ups for concurrency management happen, restore CPU affinity
 	 * of all workers first and then clear UNBOUND.  As we're called
 	 * from CPU_ONLINE, the following shouldn't fail.
 	 */
@@ -4698,6 +4722,82 @@ out_unlock:
 }
 #endif /* CONFIG_FREEZER */
 
+static int workqueue_apply_unbound_cpumask(void)
+{
+	LIST_HEAD(ctxs);
+	int ret = 0;
+	struct workqueue_struct *wq;
+	struct apply_wqattrs_ctx *ctx, *n;
+
+	lockdep_assert_held(&wq_pool_mutex);
+
+	list_for_each_entry(wq, &workqueues, list) {
+		if (!(wq->flags & WQ_UNBOUND))
+			continue;
+		/* creating multiple pwqs breaks ordering guarantee */
+		if (wq->flags & __WQ_ORDERED)
+			continue;
+
+		ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
+		if (!ctx) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		list_add_tail(&ctx->list, &ctxs);
+	}
+
+	list_for_each_entry_safe(ctx, n, &ctxs, list) {
+		if (!ret)
+			apply_wqattrs_commit(ctx);
+		apply_wqattrs_cleanup(ctx);
+	}
+
+	return ret;
+}
+
+/**
+ *  workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
+ *  @cpumask: the cpumask to set
+ *
+ *  The low-level workqueues cpumask is a global cpumask that limits
+ *  the affinity of all unbound workqueues.  This function check the @cpumask
+ *  and apply it to all unbound workqueues and updates all pwqs of them.
+ *
+ *  Retun:	0	- Success
+ *  		-EINVAL	- Invalid @cpumask
+ *  		-ENOMEM	- Failed to allocate memory for attrs or pwqs.
+ */
+int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
+{
+	int ret = -EINVAL;
+	cpumask_var_t saved_cpumask;
+
+	if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
+		return -ENOMEM;
+
+	cpumask_and(cpumask, cpumask, cpu_possible_mask);
+	if (!cpumask_empty(cpumask)) {
+		apply_wqattrs_lock();
+
+		/* save the old wq_unbound_cpumask. */
+		cpumask_copy(saved_cpumask, wq_unbound_cpumask);
+
+		/* update wq_unbound_cpumask at first and apply it to wqs. */
+		cpumask_copy(wq_unbound_cpumask, cpumask);
+		ret = workqueue_apply_unbound_cpumask();
+
+		/* restore the wq_unbound_cpumask when failed. */
+		if (ret < 0)
+			cpumask_copy(wq_unbound_cpumask, saved_cpumask);
+
+		apply_wqattrs_unlock();
+	}
+
+	free_cpumask_var(saved_cpumask);
+	return ret;
+}
+
 #ifdef CONFIG_SYSFS
 /*
  * Workqueues with WQ_SYSFS flag set is visible to userland via
@@ -4802,13 +4902,13 @@ static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
 {
 	struct workqueue_attrs *attrs;
 
+	lockdep_assert_held(&wq_pool_mutex);
+
 	attrs = alloc_workqueue_attrs(GFP_KERNEL);
 	if (!attrs)
 		return NULL;
 
-	mutex_lock(&wq->mutex);
 	copy_workqueue_attrs(attrs, wq->unbound_attrs);
-	mutex_unlock(&wq->mutex);
 	return attrs;
 }
 
@@ -4817,18 +4917,22 @@ static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 	struct workqueue_attrs *attrs;
-	int ret;
+	int ret = -ENOMEM;
+
+	apply_wqattrs_lock();
 
 	attrs = wq_sysfs_prep_attrs(wq);
 	if (!attrs)
-		return -ENOMEM;
+		goto out_unlock;
 
 	if (sscanf(buf, "%d", &attrs->nice) == 1 &&
 	    attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
-		ret = apply_workqueue_attrs(wq, attrs);
+		ret = apply_workqueue_attrs_locked(wq, attrs);
 	else
 		ret = -EINVAL;
 
+out_unlock:
+	apply_wqattrs_unlock();
 	free_workqueue_attrs(attrs);
 	return ret ?: count;
 }
@@ -4852,16 +4956,20 @@ static ssize_t wq_cpumask_store(struct device *dev,
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 	struct workqueue_attrs *attrs;
-	int ret;
+	int ret = -ENOMEM;
+
+	apply_wqattrs_lock();
 
 	attrs = wq_sysfs_prep_attrs(wq);
 	if (!attrs)
-		return -ENOMEM;
+		goto out_unlock;
 
 	ret = cpumask_parse(buf, attrs->cpumask);
 	if (!ret)
-		ret = apply_workqueue_attrs(wq, attrs);
+		ret = apply_workqueue_attrs_locked(wq, attrs);
 
+out_unlock:
+	apply_wqattrs_unlock();
 	free_workqueue_attrs(attrs);
 	return ret ?: count;
 }
@@ -4885,18 +4993,22 @@ static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 	struct workqueue_attrs *attrs;
-	int v, ret;
+	int v, ret = -ENOMEM;
+
+	apply_wqattrs_lock();
 
 	attrs = wq_sysfs_prep_attrs(wq);
 	if (!attrs)
-		return -ENOMEM;
+		goto out_unlock;
 
 	ret = -EINVAL;
 	if (sscanf(buf, "%d", &v) == 1) {
 		attrs->no_numa = !v;
-		ret = apply_workqueue_attrs(wq, attrs);
+		ret = apply_workqueue_attrs_locked(wq, attrs);
 	}
 
+out_unlock:
+	apply_wqattrs_unlock();
 	free_workqueue_attrs(attrs);
 	return ret ?: count;
 }
@@ -4914,9 +5026,49 @@ static struct bus_type wq_subsys = {
 	.dev_groups			= wq_sysfs_groups,
 };
 
+static ssize_t wq_unbound_cpumask_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	int written;
+
+	mutex_lock(&wq_pool_mutex);
+	written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
+			    cpumask_pr_args(wq_unbound_cpumask));
+	mutex_unlock(&wq_pool_mutex);
+
+	return written;
+}
+
+static ssize_t wq_unbound_cpumask_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	cpumask_var_t cpumask;
+	int ret;
+
+	if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
+		return -ENOMEM;
+
+	ret = cpumask_parse(buf, cpumask);
+	if (!ret)
+		ret = workqueue_set_unbound_cpumask(cpumask);
+
+	free_cpumask_var(cpumask);
+	return ret ? ret : count;
+}
+
+static struct device_attribute wq_sysfs_cpumask_attr =
+	__ATTR(cpumask, 0644, wq_unbound_cpumask_show,
+	       wq_unbound_cpumask_store);
+
 static int __init wq_sysfs_init(void)
 {
-	return subsys_virtual_register(&wq_subsys, NULL);
+	int err;
+
+	err = subsys_virtual_register(&wq_subsys, NULL);
+	if (err)
+		return err;
+
+	return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
 }
 core_initcall(wq_sysfs_init);
 
@@ -4948,7 +5100,7 @@ int workqueue_sysfs_register(struct workqueue_struct *wq)
 	int ret;
 
 	/*
-	 * Adjusting max_active or creating new pwqs by applyting
+	 * Adjusting max_active or creating new pwqs by applying
 	 * attributes breaks ordering guarantee.  Disallow exposing ordered
 	 * workqueues.
 	 */
@@ -5064,6 +5216,9 @@ static int __init init_workqueues(void)
 
 	WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
 
+	BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
+	cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
+
 	pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
 
 	cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);