---

yaml
---
r: 206225
b: refs/heads/master
c: 7e11629
h: refs/heads/master
i:
  206223: bea4476
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 18aa9effad4adb2c1efe123af4eb24fec9f59b30
+refs/heads/master: 7e11629d0efec829cbf62366143ba1081944a70e

trunk/kernel/workqueue.c

@@ -34,6 +34,7 @@
 #include <linux/debug_locks.h>
 #include <linux/lockdep.h>
 #include <linux/idr.h>
+#include <linux/delay.h>
 
 enum {
 	/* global_cwq flags */
@@ -72,7 +73,6 @@ enum {
  */
 
 struct global_cwq;
-struct cpu_workqueue_struct;
 
 struct worker {
 	/* on idle list while idle, on busy hash table while busy */
@@ -86,7 +86,6 @@ struct worker {
 	struct list_head	scheduled;	/* L: scheduled works */
 	struct task_struct	*task;		/* I: worker task */
 	struct global_cwq	*gcwq;		/* I: the associated gcwq */
-	struct cpu_workqueue_struct *cwq;	/* I: the associated cwq */
 	unsigned int		flags;		/* L: flags */
 	int			id;		/* I: worker id */
 };
@@ -96,6 +95,7 @@ struct worker {
  */
 struct global_cwq {
 	spinlock_t		lock;		/* the gcwq lock */
+	struct list_head	worklist;	/* L: list of pending works */
 	unsigned int		cpu;		/* I: the associated cpu */
 	unsigned int		flags;		/* L: GCWQ_* flags */
 
@@ -121,7 +121,6 @@ struct global_cwq {
  */
 struct cpu_workqueue_struct {
 	struct global_cwq	*gcwq;		/* I: the associated gcwq */
-	struct list_head worklist;
 	struct worker		*worker;
 	struct workqueue_struct *wq;		/* I: the owning workqueue */
 	int			work_color;	/* L: current color */
@@ -386,6 +385,32 @@ static struct global_cwq *get_work_gcwq(struct work_struct *work)
 	return get_gcwq(cpu);
 }
 
+/* Return the first worker.  Safe with preemption disabled */
+static struct worker *first_worker(struct global_cwq *gcwq)
+{
+	if (unlikely(list_empty(&gcwq->idle_list)))
+		return NULL;
+
+	return list_first_entry(&gcwq->idle_list, struct worker, entry);
+}
+
+/**
+ * wake_up_worker - wake up an idle worker
+ * @gcwq: gcwq to wake worker for
+ *
+ * Wake up the first idle worker of @gcwq.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ */
+static void wake_up_worker(struct global_cwq *gcwq)
+{
+	struct worker *worker = first_worker(gcwq);
+
+	if (likely(worker))
+		wake_up_process(worker->task);
+}
+
 /**
  * busy_worker_head - return the busy hash head for a work
  * @gcwq: gcwq of interest
@@ -467,13 +492,14 @@ static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
 }
 
 /**
- * insert_work - insert a work into cwq
+ * insert_work - insert a work into gcwq
  * @cwq: cwq @work belongs to
  * @work: work to insert
  * @head: insertion point
  * @extra_flags: extra WORK_STRUCT_* flags to set
  *
- * Insert @work into @cwq after @head.
+ * Insert @work which belongs to @cwq into @gcwq after @head.
+ * @extra_flags is or'd to work_struct flags.
  *
  * CONTEXT:
  * spin_lock_irq(gcwq->lock).
@@ -492,7 +518,7 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
 	smp_wmb();
 
 	list_add_tail(&work->entry, head);
-	wake_up_process(cwq->worker->task);
+	wake_up_worker(cwq->gcwq);
 }
 
 /**
@@ -608,7 +634,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 
 	if (likely(cwq->nr_active < cwq->max_active)) {
 		cwq->nr_active++;
-		worklist = &cwq->worklist;
+		worklist = &gcwq->worklist;
 	} else
 		worklist = &cwq->delayed_works;
 
@@ -793,10 +819,10 @@ static struct worker *alloc_worker(void)
 
 /**
  * create_worker - create a new workqueue worker
- * @cwq: cwq the new worker will belong to
+ * @gcwq: gcwq the new worker will belong to
  * @bind: whether to set affinity to @cpu or not
  *
- * Create a new worker which is bound to @cwq.  The returned worker
+ * Create a new worker which is bound to @gcwq.  The returned worker
  * can be started by calling start_worker() or destroyed using
  * destroy_worker().
  *
@@ -806,9 +832,8 @@ static struct worker *alloc_worker(void)
  * RETURNS:
  * Pointer to the newly created worker.
  */
-static struct worker *create_worker(struct cpu_workqueue_struct *cwq, bool bind)
+static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
 {
-	struct global_cwq *gcwq = cwq->gcwq;
 	int id = -1;
 	struct worker *worker = NULL;
 
@@ -826,7 +851,6 @@ static struct worker *create_worker(struct cpu_workqueue_struct *cwq, bool bind)
 		goto fail;
 
 	worker->gcwq = gcwq;
-	worker->cwq = cwq;
 	worker->id = id;
 
 	worker->task = kthread_create(worker_thread, worker, "kworker/%u:%d",
@@ -953,7 +977,7 @@ static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
 	struct work_struct *work = list_first_entry(&cwq->delayed_works,
 						    struct work_struct, entry);
 
-	move_linked_works(work, &cwq->worklist, NULL);
+	move_linked_works(work, &cwq->gcwq->worklist, NULL);
 	cwq->nr_active++;
 }
 
@@ -1021,11 +1045,12 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color)
  */
 static void process_one_work(struct worker *worker, struct work_struct *work)
 {
-	struct cpu_workqueue_struct *cwq = worker->cwq;
+	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
 	struct global_cwq *gcwq = cwq->gcwq;
 	struct hlist_head *bwh = busy_worker_head(gcwq, work);
 	work_func_t f = work->func;
 	int work_color;
+	struct worker *collision;
 #ifdef CONFIG_LOCKDEP
 	/*
 	 * It is permissible to free the struct work_struct from
@@ -1036,14 +1061,25 @@ static void process_one_work(struct worker *worker, struct work_struct *work)
 	 */
 	struct lockdep_map lockdep_map = work->lockdep_map;
 #endif
+	/*
+	 * A single work shouldn't be executed concurrently by
+	 * multiple workers on a single cpu.  Check whether anyone is
+	 * already processing the work.  If so, defer the work to the
+	 * currently executing one.
+	 */
+	collision = __find_worker_executing_work(gcwq, bwh, work);
+	if (unlikely(collision)) {
+		move_linked_works(work, &collision->scheduled, NULL);
+		return;
+	}
+
 	/* claim and process */
 	debug_work_deactivate(work);
 	hlist_add_head(&worker->hentry, bwh);
 	worker->current_work = work;
 	worker->current_cwq = cwq;
 	work_color = get_work_color(work);
 
-	BUG_ON(get_work_cwq(work) != cwq);
 	/* record the current cpu number in the work data and dequeue */
 	set_work_cpu(work, gcwq->cpu);
 	list_del_init(&work->entry);
@@ -1107,7 +1143,6 @@ static int worker_thread(void *__worker)
 {
 	struct worker *worker = __worker;
 	struct global_cwq *gcwq = worker->gcwq;
-	struct cpu_workqueue_struct *cwq = worker->cwq;
 
 woke_up:
 	spin_lock_irq(&gcwq->lock);
@@ -1127,9 +1162,9 @@ static int worker_thread(void *__worker)
 	 */
 	BUG_ON(!list_empty(&worker->scheduled));
 
-	while (!list_empty(&cwq->worklist)) {
+	while (!list_empty(&gcwq->worklist)) {
 		struct work_struct *work =
-			list_first_entry(&cwq->worklist,
+			list_first_entry(&gcwq->worklist,
 					 struct work_struct, entry);
 
 		/*
@@ -1844,18 +1879,37 @@ int keventd_up(void)
 
 int current_is_keventd(void)
 {
-	struct cpu_workqueue_struct *cwq;
-	int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
-	int ret = 0;
+	bool found = false;
+	unsigned int cpu;
 
-	BUG_ON(!keventd_wq);
+	/*
+	 * There no longer is one-to-one relation between worker and
+	 * work queue and a worker task might be unbound from its cpu
+	 * if the cpu was offlined.  Match all busy workers.  This
+	 * function will go away once dynamic pool is implemented.
+	 */
+	for_each_possible_cpu(cpu) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct worker *worker;
+		struct hlist_node *pos;
+		unsigned long flags;
+		int i;
 
-	cwq = get_cwq(cpu, keventd_wq);
-	if (current == cwq->worker->task)
-		ret = 1;
+		spin_lock_irqsave(&gcwq->lock, flags);
 
-	return ret;
+		for_each_busy_worker(worker, i, pos, gcwq) {
+			if (worker->task == current) {
+				found = true;
+				break;
+			}
+		}
+
+		spin_unlock_irqrestore(&gcwq->lock, flags);
+		if (found)
+			break;
+	}
 
+	return found;
 }
 
 static struct cpu_workqueue_struct *alloc_cwqs(void)
@@ -1953,12 +2007,11 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
 		cwq->wq = wq;
 		cwq->flush_color = -1;
 		cwq->max_active = max_active;
-		INIT_LIST_HEAD(&cwq->worklist);
 		INIT_LIST_HEAD(&cwq->delayed_works);
 
 		if (failed)
 			continue;
-		cwq->worker = create_worker(cwq, cpu_online(cpu));
+		cwq->worker = create_worker(gcwq, cpu_online(cpu));
 		if (cwq->worker)
 			start_worker(cwq->worker);
 		else
@@ -2020,13 +2073,26 @@ void destroy_workqueue(struct workqueue_struct *wq)
 
 	for_each_possible_cpu(cpu) {
 		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+		struct global_cwq *gcwq = cwq->gcwq;
 		int i;
 
 		if (cwq->worker) {
-			spin_lock_irq(&cwq->gcwq->lock);
+		retry:
+			spin_lock_irq(&gcwq->lock);
+			/*
+			 * Worker can only be destroyed while idle.
+			 * Wait till it becomes idle.  This is ugly
+			 * and prone to starvation.  It will go away
+			 * once dynamic worker pool is implemented.
+			 */
+			if (!(cwq->worker->flags & WORKER_IDLE)) {
+				spin_unlock_irq(&gcwq->lock);
+				msleep(100);
+				goto retry;
+			}
 			destroy_worker(cwq->worker);
 			cwq->worker = NULL;
-			spin_unlock_irq(&cwq->gcwq->lock);
+			spin_unlock_irq(&gcwq->lock);
 		}
 
 		for (i = 0; i < WORK_NR_COLORS; i++)
@@ -2324,7 +2390,7 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
  *
  * Start freezing workqueues.  After this function returns, all
  * freezeable workqueues will queue new works to their frozen_works
- * list instead of the cwq ones.
+ * list instead of gcwq->worklist.
  *
  * CONTEXT:
  * Grabs and releases workqueue_lock and gcwq->lock's.
@@ -2410,7 +2476,7 @@ bool freeze_workqueues_busy(void)
  * thaw_workqueues - thaw workqueues
  *
  * Thaw workqueues.  Normal queueing is restored and all collected
- * frozen works are transferred to their respective cwq worklists.
+ * frozen works are transferred to their respective gcwq worklists.
  *
  * CONTEXT:
  * Grabs and releases workqueue_lock and gcwq->lock's.
@@ -2483,6 +2549,7 @@ void __init init_workqueues(void)
 		struct global_cwq *gcwq = get_gcwq(cpu);
 
 		spin_lock_init(&gcwq->lock);
+		INIT_LIST_HEAD(&gcwq->worklist);
 		gcwq->cpu = cpu;
 
 		INIT_LIST_HEAD(&gcwq->idle_list);