Merge branches 'pm-opp-fixes', 'pm-cpufreq-fixes' and 'pm-cpuidle-fixes'

[deliverable/linux.git] / kernel / workqueue.c

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 16e13d8628a301c61e2178df18756ba7483d4941..3bfdff06eea728b38364652808e9f548f0e6fe37 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -666,6 +666,35 @@ static void set_work_pool_and_clear_pending(struct work_struct *work,
         */
        smp_wmb();
        set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
+       /*
+        * The following mb guarantees that previous clear of a PENDING bit
+        * will not be reordered with any speculative LOADS or STORES from
+        * work->current_func, which is executed afterwards.  This possible
+        * reordering can lead to a missed execution on attempt to qeueue
+        * the same @work.  E.g. consider this case:
+        *
+        *   CPU#0                         CPU#1
+        *   ----------------------------  --------------------------------
+        *
+        * 1  STORE event_indicated
+        * 2  queue_work_on() {
+        * 3    test_and_set_bit(PENDING)
+        * 4 }                             set_..._and_clear_pending() {
+        * 5                                 set_work_data() # clear bit
+        * 6                                 smp_mb()
+        * 7                               work->current_func() {
+        * 8                                  LOAD event_indicated
+        *                                 }
+        *
+        * Without an explicit full barrier speculative LOAD on line 8 can
+        * be executed before CPU#0 does STORE on line 1.  If that happens,
+        * CPU#0 observes the PENDING bit is still set and new execution of
+        * a @work is not queued in a hope, that CPU#1 will eventually
+        * finish the queued @work.  Meanwhile CPU#1 does not see
+        * event_indicated is set, because speculative LOAD was executed
+        * before actual STORE.
+        */
+       smp_mb();
 }
 
 static void clear_work_data(struct work_struct *work)
@@ -857,7 +886,6 @@ void wq_worker_waking_up(struct task_struct *task, int cpu)
 /**
  * wq_worker_sleeping - a worker is going to sleep
  * @task: task going to sleep
- * @cpu: CPU in question, must be the current CPU number
  *
  * This function is called during schedule() when a busy worker is
  * going to sleep.  Worker on the same cpu can be woken up by
@@ -869,7 +897,7 @@ void wq_worker_waking_up(struct task_struct *task, int cpu)
  * Return:
  * Worker task on @cpu to wake up, %NULL if none.
  */
-struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu)
+struct task_struct *wq_worker_sleeping(struct task_struct *task)
 {
        struct worker *worker = kthread_data(task), *to_wakeup = NULL;
        struct worker_pool *pool;
@@ -885,7 +913,7 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu)
        pool = worker->pool;
 
        /* this can only happen on the local cpu */
-       if (WARN_ON_ONCE(cpu != raw_smp_processor_id() || pool->cpu != cpu))
+       if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
                return NULL;
 
        /*
@@ -4695,7 +4723,7 @@ static void work_for_cpu_fn(struct work_struct *work)
 }
 
 /**
- * work_on_cpu - run a function in user context on a particular cpu
+ * work_on_cpu - run a function in thread context on a particular cpu
  * @cpu: the cpu to run on
  * @fn: the function to run
  * @arg: the function arg
@@ -5221,8 +5249,8 @@ int workqueue_sysfs_register(struct workqueue_struct *wq)
 
        wq_dev->wq = wq;
        wq_dev->dev.bus = &wq_subsys;
-       wq_dev->dev.init_name = wq->name;
        wq_dev->dev.release = wq_device_release;
+       dev_set_name(&wq_dev->dev, "%s", wq->name);
 
        /*
         * unbound_attrs are created separately.  Suppress uevent until