1 files changed, 60 insertions, 24 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 10f655e..29b7985 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2205,6 +2205,15 @@ __acquires(&pool->lock)
 		dump_stack();
 	}
 
+	/*
+	 * The following prevents a kworker from hogging CPU on !PREEMPT
+	 * kernels, where a requeueing work item waiting for something to
+	 * happen could deadlock with stop_machine as such work item could
+	 * indefinitely requeue itself while all other CPUs are trapped in
+	 * stop_machine.
+	 */
+	cond_resched();
+
 	spin_lock_irq(&pool->lock);
 
 	/* clear cpu intensive status */
@@ -2821,6 +2830,19 @@ already_gone:
 	return false;
 }
 
+static bool __flush_work(struct work_struct *work)
+{
+	struct wq_barrier barr;
+
+	if (start_flush_work(work, &barr)) {
+		wait_for_completion(&barr.done);
+		destroy_work_on_stack(&barr.work);
+		return true;
+	} else {
+		return false;
+	}
+}
+
 /**
  * flush_work - wait for a work to finish executing the last queueing instance
  * @work: the work to flush
@@ -2834,18 +2856,10 @@ already_gone:
  */
 bool flush_work(struct work_struct *work)
 {
-	struct wq_barrier barr;
-
 	lock_map_acquire(&work->lockdep_map);
 	lock_map_release(&work->lockdep_map);
 
-	if (start_flush_work(work, &barr)) {
-		wait_for_completion(&barr.done);
-		destroy_work_on_stack(&barr.work);
-		return true;
-	} else {
-		return false;
-	}
+	return __flush_work(work);
 }
 EXPORT_SYMBOL_GPL(flush_work);
 
@@ -3085,25 +3099,26 @@ static struct workqueue_struct *dev_to_wq(struct device *dev)
 	return wq_dev->wq;
 }
 
-static ssize_t wq_per_cpu_show(struct device *dev,
-			       struct device_attribute *attr, char *buf)
+static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 
 	return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
 }
+static DEVICE_ATTR_RO(per_cpu);
 
-static ssize_t wq_max_active_show(struct device *dev,
-				  struct device_attribute *attr, char *buf)
+static ssize_t max_active_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 
 	return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
 }
 
-static ssize_t wq_max_active_store(struct device *dev,
-				   struct device_attribute *attr,
-				   const char *buf, size_t count)
+static ssize_t max_active_store(struct device *dev,
+				struct device_attribute *attr, const char *buf,
+				size_t count)
 {
 	struct workqueue_struct *wq = dev_to_wq(dev);
 	int val;
@@ -3114,12 +3129,14 @@ static ssize_t wq_max_active_store(struct device *dev,
 	workqueue_set_max_active(wq, val);
 	return count;
 }
+static DEVICE_ATTR_RW(max_active);
 
-static struct device_attribute wq_sysfs_attrs[] = {
-	__ATTR(per_cpu, 0444, wq_per_cpu_show, NULL),
-	__ATTR(max_active, 0644, wq_max_active_show, wq_max_active_store),
-	__ATTR_NULL,
+static struct attribute *wq_sysfs_attrs[] = {
+	&dev_attr_per_cpu.attr,
+	&dev_attr_max_active.attr,
+	NULL,
 };
+ATTRIBUTE_GROUPS(wq_sysfs);
 
 static ssize_t wq_pool_ids_show(struct device *dev,
 				struct device_attribute *attr, char *buf)
@@ -3269,7 +3286,7 @@ static struct device_attribute wq_sysfs_unbound_attrs[] = {
 
 static struct bus_type wq_subsys = {
 	.name				= "workqueue",
-	.dev_attrs			= wq_sysfs_attrs,
+	.dev_groups			= wq_sysfs_groups,
 };
 
 static int __init wq_sysfs_init(void)
@@ -3415,6 +3432,12 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
 {
 	to->nice = from->nice;
 	cpumask_copy(to->cpumask, from->cpumask);
+	/*
+	 * Unlike hash and equality test, this function doesn't ignore
+	 * ->no_numa as it is used for both pool and wq attrs.  Instead,
+	 * get_unbound_pool() explicitly clears ->no_numa after copying.
+	 */
+	to->no_numa = from->no_numa;
 }
 
 /* hash value of the content of @attr */
@@ -3582,6 +3605,12 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
 	lockdep_set_subclass(&pool->lock, 1);	/* see put_pwq() */
 	copy_workqueue_attrs(pool->attrs, attrs);
 
+	/*
+	 * no_numa isn't a worker_pool attribute, always clear it.  See
+	 * 'struct workqueue_attrs' comments for detail.
+	 */
+	pool->attrs->no_numa = false;
+
 	/* if cpumask is contained inside a NUMA node, we belong to that node */
 	if (wq_numa_enabled) {
 		for_each_node(node) {
@@ -4648,7 +4677,7 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
  * Workqueues should be brought up before normal priority CPU notifiers.
  * This will be registered high priority CPU notifier.
  */
-static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb,
+static int workqueue_cpu_up_callback(struct notifier_block *nfb,
 					       unsigned long action,
 					       void *hcpu)
 {
@@ -4701,7 +4730,7 @@ static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb,
  * Workqueues should be brought down after normal priority CPU notifiers.
  * This will be registered as low priority CPU notifier.
  */
-static int __cpuinit workqueue_cpu_down_callback(struct notifier_block *nfb,
+static int workqueue_cpu_down_callback(struct notifier_block *nfb,
 						 unsigned long action,
 						 void *hcpu)
 {
@@ -4760,7 +4789,14 @@ long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
 
 	INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
 	schedule_work_on(cpu, &wfc.work);
-	flush_work(&wfc.work);
+
+	/*
+	 * The work item is on-stack and can't lead to deadlock through
+	 * flushing.  Use __flush_work() to avoid spurious lockdep warnings
+	 * when work_on_cpu()s are nested.
+	 */
+	__flush_work(&wfc.work);
+
 	return wfc.ret;
 }
 EXPORT_SYMBOL_GPL(work_on_cpu);