Merge branch 'x86-paravirt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[platform/kernel/linux-arm64.git] / kernel / workqueue.c

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 7f5d4be..29b7985 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -16,9 +16,10 @@
  *
  * This is the generic async execution mechanism.  Work items as are
  * executed in process context.  The worker pool is shared and
- * automatically managed.  There is one worker pool for each CPU and
- * one extra for works which are better served by workers which are
- * not bound to any specific CPU.
+ * automatically managed.  There are two worker pools for each CPU (one for
+ * normal work items and the other for high priority ones) and some extra
+ * pools for workqueues which are not bound to any specific CPU - the
+ * number of these backing pools is dynamic.
  *
  * Please read Documentation/workqueue.txt for details.
  */
@@ -2033,8 +2034,11 @@ static bool maybe_destroy_workers(struct worker_pool *pool)
  * multiple times.  Does GFP_KERNEL allocations.
  *
  * RETURNS:
- * spin_lock_irq(pool->lock) which may be released and regrabbed
- * multiple times.  Does GFP_KERNEL allocations.
+ * %false if the pool don't need management and the caller can safely start
+ * processing works, %true indicates that the function released pool->lock
+ * and reacquired it to perform some management function and that the
+ * conditions that the caller verified while holding the lock before
+ * calling the function might no longer be true.
  */
 static bool manage_workers(struct worker *worker)
 {
@@ -2201,6 +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 */
@@ -3086,25 +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;
@@ -3115,12 +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)
@@ -3270,7 +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)