workqueue: separate out process_one_work()

Separate out process_one_work() out of run_workqueue().  This patch
doesn't cause any behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/workqueue.c

@@ -402,28 +402,40 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 }
 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 
-static void run_workqueue(struct cpu_workqueue_struct *cwq)
+/**
+ * process_one_work - process single work
+ * @cwq: cwq to process work for
+ * @work: work to process
+ *
+ * Process @work.  This function contains all the logics necessary to
+ * process a single work including synchronization against and
+ * interaction with other workers on the same cpu, queueing and
+ * flushing.  As long as context requirement is met, any worker can
+ * call this function to process a work.
+ *
+ * CONTEXT:
+ * spin_lock_irq(cwq->lock) which is released and regrabbed.
+ */
+static void process_one_work(struct cpu_workqueue_struct *cwq,
+			     struct work_struct *work)
 {
-	spin_lock_irq(&cwq->lock);
-	while (!list_empty(&cwq->worklist)) {
-		struct work_struct *work = list_entry(cwq->worklist.next,
-						struct work_struct, entry);
 	work_func_t f = work->func;
 #ifdef CONFIG_LOCKDEP
 	/*
-		 * It is permissible to free the struct work_struct
-		 * from inside the function that is called from it,
-		 * this we need to take into account for lockdep too.
-		 * To avoid bogus "held lock freed" warnings as well
-		 * as problems when looking into work->lockdep_map,
-		 * make a copy and use that here.
+	 * It is permissible to free the struct work_struct from
+	 * inside the function that is called from it, this we need to
+	 * take into account for lockdep too.  To avoid bogus "held
+	 * lock freed" warnings as well as problems when looking into
+	 * work->lockdep_map, make a copy and use that here.
 	 */
 	struct lockdep_map lockdep_map = work->lockdep_map;
 #endif
+	/* claim and process */
 	trace_workqueue_execution(cwq->thread, work);
 	debug_work_deactivate(work);
 	cwq->current_work = work;
-		list_del_init(cwq->worklist.next);
+	list_del_init(&work->entry);
+
 	spin_unlock_irq(&cwq->lock);
 
 	BUG_ON(get_wq_data(work) != cwq);
@@ -437,8 +449,7 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq)
 	if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
 		printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
 		       "%s/0x%08x/%d\n",
-					current->comm, preempt_count(),
-				       	task_pid_nr(current));
+		       current->comm, preempt_count(), task_pid_nr(current));
 		printk(KERN_ERR "    last function: ");
 		print_symbol("%s\n", (unsigned long)f);
 		debug_show_held_locks(current);
@@ -446,7 +457,18 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq)
 	}
 
 	spin_lock_irq(&cwq->lock);
+
+	/* we're done with it, release */
 	cwq->current_work = NULL;
+}
+
+static void run_workqueue(struct cpu_workqueue_struct *cwq)
+{
+	spin_lock_irq(&cwq->lock);
+	while (!list_empty(&cwq->worklist)) {
+		struct work_struct *work = list_entry(cwq->worklist.next,
+						struct work_struct, entry);
+		process_one_work(cwq, work);
 	}
 	spin_unlock_irq(&cwq->lock);
 }