Merge branch 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull workqueue changes from Tejun Heo:
 "There are three major changes.

   - WQ_HIGHPRI has been reimplemented so that high priority work items
     are served by worker threads with -20 nice value from dedicated
     highpri worker pools.

   - CPU hotplug support has been reimplemented such that idle workers
     are kept across CPU hotplug events.  This makes CPU hotplug cheaper
     (for PM) and makes the code simpler.

   - flush_kthread_work() has been reimplemented so that a work item can
     be freed while executing.  This removes an annoying behavior
     difference between kthread_worker and workqueue."

* 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: fix spurious CPU locality WARN from process_one_work()
  kthread_worker: reimplement flush_kthread_work() to allow freeing the work item being executed
  kthread_worker: reorganize to prepare for flush_kthread_work() reimplementation
  workqueue: simplify CPU hotplug code
  workqueue: remove CPU offline trustee
  workqueue: don't butcher idle workers on an offline CPU
  workqueue: reimplement CPU online rebinding to handle idle workers
  workqueue: drop @bind from create_worker()
  workqueue: use mutex for global_cwq manager exclusion
  workqueue: ROGUE workers are UNBOUND workers
  workqueue: drop CPU_DYING notifier operation
  workqueue: perform cpu down operations from low priority cpu_notifier()
  workqueue: reimplement WQ_HIGHPRI using a separate worker_pool
  workqueue: introduce NR_WORKER_POOLS and for_each_worker_pool()
  workqueue: separate out worker_pool flags
  workqueue: use @pool instead of @gcwq or @cpu where applicable
  workqueue: factor out worker_pool from global_cwq
  workqueue: don't use WQ_HIGHPRI for unbound workqueues

2 files changed, 584 insertions, 648 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3d3de633702..b579af57ea1 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -360,16 +360,12 @@ repeat:
 					struct kthread_work, node);
 		list_del_init(&work->node);
 	}
+	worker->current_work = work;
 	spin_unlock_irq(&worker->lock);
 
 	if (work) {
 		__set_current_state(TASK_RUNNING);
 		work->func(work);
-		smp_wmb();	/* wmb worker-b0 paired with flush-b1 */
-		work->done_seq = work->queue_seq;
-		smp_mb();	/* mb worker-b1 paired with flush-b0 */
-		if (atomic_read(&work->flushing))
-			wake_up_all(&work->done);
 	} else if (!freezing(current))
 		schedule();
 
@@ -378,6 +374,19 @@ repeat:
 }
 EXPORT_SYMBOL_GPL(kthread_worker_fn);
 
+/* insert @work before @pos in @worker */
+static void insert_kthread_work(struct kthread_worker *worker,
+			       struct kthread_work *work,
+			       struct list_head *pos)
+{
+	lockdep_assert_held(&worker->lock);
+
+	list_add_tail(&work->node, pos);
+	work->worker = worker;
+	if (likely(worker->task))
+		wake_up_process(worker->task);
+}
+
 /**
  * queue_kthread_work - queue a kthread_work
  * @worker: target kthread_worker
@@ -395,10 +404,7 @@ bool queue_kthread_work(struct kthread_worker *worker,
 
 	spin_lock_irqsave(&worker->lock, flags);
 	if (list_empty(&work->node)) {
-		list_add_tail(&work->node, &worker->work_list);
-		work->queue_seq++;
-		if (likely(worker->task))
-			wake_up_process(worker->task);
+		insert_kthread_work(worker, work, &worker->work_list);
 		ret = true;
 	}
 	spin_unlock_irqrestore(&worker->lock, flags);
@@ -406,6 +412,18 @@ bool queue_kthread_work(struct kthread_worker *worker,
 }
 EXPORT_SYMBOL_GPL(queue_kthread_work);
 
+struct kthread_flush_work {
+	struct kthread_work	work;
+	struct completion	done;
+};
+
+static void kthread_flush_work_fn(struct kthread_work *work)
+{
+	struct kthread_flush_work *fwork =
+		container_of(work, struct kthread_flush_work, work);
+	complete(&fwork->done);
+}
+
 /**
  * flush_kthread_work - flush a kthread_work
  * @work: work to flush
@@ -414,39 +432,37 @@ EXPORT_SYMBOL_GPL(queue_kthread_work);
  */
 void flush_kthread_work(struct kthread_work *work)
 {
-	int seq = work->queue_seq;
-
-	atomic_inc(&work->flushing);
+	struct kthread_flush_work fwork = {
+		KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
+		COMPLETION_INITIALIZER_ONSTACK(fwork.done),
+	};
+	struct kthread_worker *worker;
+	bool noop = false;
 
-	/*
-	 * mb flush-b0 paired with worker-b1, to make sure either
-	 * worker sees the above increment or we see done_seq update.
-	 */
-	smp_mb__after_atomic_inc();
+retry:
+	worker = work->worker;
+	if (!worker)
+		return;
 
-	/* A - B <= 0 tests whether B is in front of A regardless of overflow */
-	wait_event(work->done, seq - work->done_seq <= 0);
-	atomic_dec(&work->flushing);
+	spin_lock_irq(&worker->lock);
+	if (work->worker != worker) {
+		spin_unlock_irq(&worker->lock);
+		goto retry;
+	}
 
-	/*
-	 * rmb flush-b1 paired with worker-b0, to make sure our caller
-	 * sees every change made by work->func().
-	 */
-	smp_mb__after_atomic_dec();
-}
-EXPORT_SYMBOL_GPL(flush_kthread_work);
+	if (!list_empty(&work->node))
+		insert_kthread_work(worker, &fwork.work, work->node.next);
+	else if (worker->current_work == work)
+		insert_kthread_work(worker, &fwork.work, worker->work_list.next);
+	else
+		noop = true;
 
-struct kthread_flush_work {
-	struct kthread_work	work;
-	struct completion	done;
-};
+	spin_unlock_irq(&worker->lock);
 
-static void kthread_flush_work_fn(struct kthread_work *work)
-{
-	struct kthread_flush_work *fwork =
-		container_of(work, struct kthread_flush_work, work);
-	complete(&fwork->done);
+	if (!noop)
+		wait_for_completion(&fwork.done);
 }
+EXPORT_SYMBOL_GPL(flush_kthread_work);
 
 /**
  * flush_kthread_worker - flush all current works on a kthread_worker
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9a3128dc67d..692d97628a1 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -45,32 +45,41 @@
 #include "workqueue_sched.h"
 
 enum {
-	/* global_cwq flags */
-	GCWQ_MANAGE_WORKERS	= 1 << 0,	/* need to manage workers */
-	GCWQ_MANAGING_WORKERS	= 1 << 1,	/* managing workers */
-	GCWQ_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */
-	GCWQ_FREEZING		= 1 << 3,	/* freeze in progress */
-	GCWQ_HIGHPRI_PENDING	= 1 << 4,	/* highpri works on queue */
+	/*
+	 * global_cwq flags
+	 *
+	 * A bound gcwq is either associated or disassociated with its CPU.
+	 * While associated (!DISASSOCIATED), all workers are bound to the
+	 * CPU and none has %WORKER_UNBOUND set and concurrency management
+	 * is in effect.
+	 *
+	 * While DISASSOCIATED, the cpu may be offline and all workers have
+	 * %WORKER_UNBOUND set and concurrency management disabled, and may
+	 * be executing on any CPU.  The gcwq behaves as an unbound one.
+	 *
+	 * Note that DISASSOCIATED can be flipped only while holding
+	 * managership of all pools on the gcwq to avoid changing binding
+	 * state while create_worker() is in progress.
+	 */
+	GCWQ_DISASSOCIATED	= 1 << 0,	/* cpu can't serve workers */
+	GCWQ_FREEZING		= 1 << 1,	/* freeze in progress */
+
+	/* pool flags */
+	POOL_MANAGE_WORKERS	= 1 << 0,	/* need to manage workers */
 
 	/* worker flags */
 	WORKER_STARTED		= 1 << 0,	/* started */
 	WORKER_DIE		= 1 << 1,	/* die die die */
 	WORKER_IDLE		= 1 << 2,	/* is idle */
 	WORKER_PREP		= 1 << 3,	/* preparing to run works */
-	WORKER_ROGUE		= 1 << 4,	/* not bound to any cpu */
 	WORKER_REBIND		= 1 << 5,	/* mom is home, come back */
 	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */
 	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */
 
-	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
-				  WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
+	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_REBIND | WORKER_UNBOUND |
+				  WORKER_CPU_INTENSIVE,
 
-	/* gcwq->trustee_state */
-	TRUSTEE_START		= 0,		/* start */
-	TRUSTEE_IN_CHARGE	= 1,		/* trustee in charge of gcwq */
-	TRUSTEE_BUTCHER		= 2,		/* butcher workers */
-	TRUSTEE_RELEASE		= 3,		/* release workers */
-	TRUSTEE_DONE		= 4,		/* trustee is done */
+	NR_WORKER_POOLS		= 2,		/* # worker pools per gcwq */
 
 	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
 	BUSY_WORKER_HASH_SIZE	= 1 << BUSY_WORKER_HASH_ORDER,
@@ -84,13 +93,13 @@ enum {
 						   (min two ticks) */
 	MAYDAY_INTERVAL		= HZ / 10,	/* and then every 100ms */
 	CREATE_COOLDOWN		= HZ,		/* time to breath after fail */
-	TRUSTEE_COOLDOWN	= HZ / 10,	/* for trustee draining */
 
 	/*
 	 * Rescue workers are used only on emergencies and shared by
 	 * all cpus.  Give -20.
 	 */
 	RESCUER_NICE_LEVEL	= -20,
+	HIGHPRI_NICE_LEVEL	= -20,
 };
 
 /*
@@ -115,6 +124,8 @@ enum {
  */
 
 struct global_cwq;
+struct worker_pool;
+struct idle_rebind;
 
 /*
  * The poor guys doing the actual heavy lifting.  All on-duty workers
@@ -131,12 +142,31 @@ struct worker {
 	struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
 	struct list_head	scheduled;	/* L: scheduled works */
 	struct task_struct	*task;		/* I: worker task */
-	struct global_cwq	*gcwq;		/* I: the associated gcwq */
+	struct worker_pool	*pool;		/* I: the associated pool */
 	/* 64 bytes boundary on 64bit, 32 on 32bit */
 	unsigned long		last_active;	/* L: last active timestamp */
 	unsigned int		flags;		/* X: flags */
 	int			id;		/* I: worker id */
-	struct work_struct	rebind_work;	/* L: rebind worker to cpu */
+
+	/* for rebinding worker to CPU */
+	struct idle_rebind	*idle_rebind;	/* L: for idle worker */
+	struct work_struct	rebind_work;	/* L: for busy worker */
+};
+
+struct worker_pool {
+	struct global_cwq	*gcwq;		/* I: the owning gcwq */
+	unsigned int		flags;		/* X: flags */
+
+	struct list_head	worklist;	/* L: list of pending works */
+	int			nr_workers;	/* L: total number of workers */
+	int			nr_idle;	/* L: currently idle ones */
+
+	struct list_head	idle_list;	/* X: list of idle workers */
+	struct timer_list	idle_timer;	/* L: worker idle timeout */
+	struct timer_list	mayday_timer;	/* L: SOS timer for workers */
+
+	struct mutex		manager_mutex;	/* mutex manager should hold */
+	struct ida		worker_ida;	/* L: for worker IDs */
 };
 
 /*
@@ -146,27 +176,16 @@ 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 */
 
-	int			nr_workers;	/* L: total number of workers */
-	int			nr_idle;	/* L: currently idle ones */
-
-	/* workers are chained either in the idle_list or busy_hash */
-	struct list_head	idle_list;	/* X: list of idle workers */
+	/* workers are chained either in busy_hash or pool idle_list */
 	struct hlist_head	busy_hash[BUSY_WORKER_HASH_SIZE];
 						/* L: hash of busy workers */
 
-	struct timer_list	idle_timer;	/* L: worker idle timeout */
-	struct timer_list	mayday_timer;	/* L: SOS timer for dworkers */
-
-	struct ida		worker_ida;	/* L: for worker IDs */
+	struct worker_pool	pools[2];	/* normal and highpri pools */
 
-	struct task_struct	*trustee;	/* L: for gcwq shutdown */
-	unsigned int		trustee_state;	/* L: trustee state */
-	wait_queue_head_t	trustee_wait;	/* trustee wait */
-	struct worker		*first_idle;	/* L: first idle worker */
+	wait_queue_head_t	rebind_hold;	/* rebind hold wait */
 } ____cacheline_aligned_in_smp;
 
 /*
@@ -175,7 +194,7 @@ struct global_cwq {
  * aligned at two's power of the number of flag bits.
  */
 struct cpu_workqueue_struct {
-	struct global_cwq	*gcwq;		/* I: the associated gcwq */
+	struct worker_pool	*pool;		/* I: the associated pool */
 	struct workqueue_struct *wq;		/* I: the owning workqueue */
 	int			work_color;	/* L: current color */
 	int			flush_color;	/* L: flushing color */
@@ -264,6 +283,10 @@ EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);
 #define CREATE_TRACE_POINTS
 #include <trace/events/workqueue.h>
 
+#define for_each_worker_pool(pool, gcwq)				\
+	for ((pool) = &(gcwq)->pools[0];				\
+	     (pool) < &(gcwq)->pools[NR_WORKER_POOLS]; (pool)++)
+
 #define for_each_busy_worker(worker, i, pos, gcwq)			\
 	for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)			\
 		hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
@@ -444,7 +467,7 @@ static bool workqueue_freezing;		/* W: have wqs started freezing? */
  * try_to_wake_up().  Put it in a separate cacheline.
  */
 static DEFINE_PER_CPU(struct global_cwq, global_cwq);
-static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
+static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, pool_nr_running[NR_WORKER_POOLS]);
 
 /*
  * Global cpu workqueue and nr_running counter for unbound gcwq.  The
@@ -452,10 +475,17 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
  * workers have WORKER_UNBOUND set.
  */
 static struct global_cwq unbound_global_cwq;
-static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0);	/* always 0 */
+static atomic_t unbound_pool_nr_running[NR_WORKER_POOLS] = {
+	[0 ... NR_WORKER_POOLS - 1]	= ATOMIC_INIT(0),	/* always 0 */
+};
 
 static int worker_thread(void *__worker);
 
+static int worker_pool_pri(struct worker_pool *pool)
+{
+	return pool - pool->gcwq->pools;
+}
+
 static struct global_cwq *get_gcwq(unsigned int cpu)
 {
 	if (cpu != WORK_CPU_UNBOUND)
@@ -464,12 +494,15 @@ static struct global_cwq *get_gcwq(unsigned int cpu)
 		return &unbound_global_cwq;
 }
 
-static atomic_t *get_gcwq_nr_running(unsigned int cpu)
+static atomic_t *get_pool_nr_running(struct worker_pool *pool)
 {
+	int cpu = pool->gcwq->cpu;
+	int idx = worker_pool_pri(pool);
+
 	if (cpu != WORK_CPU_UNBOUND)
-		return &per_cpu(gcwq_nr_running, cpu);
+		return &per_cpu(pool_nr_running, cpu)[idx];
 	else
-		return &unbound_gcwq_nr_running;
+		return &unbound_pool_nr_running[idx];
 }
 
 static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
@@ -555,7 +588,7 @@ static struct global_cwq *get_work_gcwq(struct work_struct *work)
 
 	if (data & WORK_STRUCT_CWQ)
 		return ((struct cpu_workqueue_struct *)
-			(data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
+			(data & WORK_STRUCT_WQ_DATA_MASK))->pool->gcwq;
 
 	cpu = data >> WORK_STRUCT_FLAG_BITS;
 	if (cpu == WORK_CPU_NONE)
@@ -566,60 +599,62 @@ static struct global_cwq *get_work_gcwq(struct work_struct *work)
 }
 
 /*
- * Policy functions.  These define the policies on how the global
- * worker pool is managed.  Unless noted otherwise, these functions
- * assume that they're being called with gcwq->lock held.
+ * Policy functions.  These define the policies on how the global worker
+ * pools are managed.  Unless noted otherwise, these functions assume that
+ * they're being called with gcwq->lock held.
  */
 
-static bool __need_more_worker(struct global_cwq *gcwq)
+static bool __need_more_worker(struct worker_pool *pool)
 {
-	return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
-		gcwq->flags & GCWQ_HIGHPRI_PENDING;
+	return !atomic_read(get_pool_nr_running(pool));
 }
 
 /*
  * Need to wake up a worker?  Called from anything but currently
  * running workers.
+ *
+ * Note that, because unbound workers never contribute to nr_running, this
+ * function will always return %true for unbound gcwq as long as the
+ * worklist isn't empty.
  */
-static bool need_more_worker(struct global_cwq *gcwq)
+static bool need_more_worker(struct worker_pool *pool)
 {
-	return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
+	return !list_empty(&pool->worklist) && __need_more_worker(pool);
 }
 
 /* Can I start working?  Called from busy but !running workers. */
-static bool may_start_working(struct global_cwq *gcwq)
+static bool may_start_working(struct worker_pool *pool)
 {
-	return gcwq->nr_idle;
+	return pool->nr_idle;
 }
 
 /* Do I need to keep working?  Called from currently running workers. */
-static bool keep_working(struct global_cwq *gcwq)
+static bool keep_working(struct worker_pool *pool)
 {
-	atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
+	atomic_t *nr_running = get_pool_nr_running(pool);
 
-	return !list_empty(&gcwq->worklist) &&
-		(atomic_read(nr_running) <= 1 ||
-		 gcwq->flags & GCWQ_HIGHPRI_PENDING);
+	return !list_empty(&pool->worklist) && atomic_read(nr_running) <= 1;
 }
 
 /* Do we need a new worker?  Called from manager. */
-static bool need_to_create_worker(struct global_cwq *gcwq)
+static bool need_to_create_worker(struct worker_pool *pool)
 {
-	return need_more_worker(gcwq) && !may_start_working(gcwq);
+	return need_more_worker(pool) && !may_start_working(pool);
 }
 
 /* Do I need to be the manager? */
-static bool need_to_manage_workers(struct global_cwq *gcwq)
+static bool need_to_manage_workers(struct worker_pool *pool)
 {
-	return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
+	return need_to_create_worker(pool) ||
+		(pool->flags & POOL_MANAGE_WORKERS);
 }
 
 /* Do we have too many workers and should some go away? */
-static bool too_many_workers(struct global_cwq *gcwq)
+static bool too_many_workers(struct worker_pool *pool)
 {
-	bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
-	int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
-	int nr_busy = gcwq->nr_workers - nr_idle;
+	bool managing = mutex_is_locked(&pool->manager_mutex);
+	int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
+	int nr_busy = pool->nr_workers - nr_idle;
 
 	return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
 }
@@ -629,26 +664,26 @@ static bool too_many_workers(struct global_cwq *gcwq)
  */
 
 /* Return the first worker.  Safe with preemption disabled */
-static struct worker *first_worker(struct global_cwq *gcwq)
+static struct worker *first_worker(struct worker_pool *pool)
 {
-	if (unlikely(list_empty(&gcwq->idle_list)))
+	if (unlikely(list_empty(&pool->idle_list)))
 		return NULL;
 
-	return list_first_entry(&gcwq->idle_list, struct worker, entry);
+	return list_first_entry(&pool->idle_list, struct worker, entry);
 }
 
 /**
  * wake_up_worker - wake up an idle worker
- * @gcwq: gcwq to wake worker for
+ * @pool: worker pool to wake worker from
  *
- * Wake up the first idle worker of @gcwq.
+ * Wake up the first idle worker of @pool.
  *
  * CONTEXT:
  * spin_lock_irq(gcwq->lock).
  */
-static void wake_up_worker(struct global_cwq *gcwq)
+static void wake_up_worker(struct worker_pool *pool)
 {
-	struct worker *worker = first_worker(gcwq);
+	struct worker *worker = first_worker(pool);
 
 	if (likely(worker))
 		wake_up_process(worker->task);
@@ -670,7 +705,7 @@ void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
 	struct worker *worker = kthread_data(task);
 
 	if (!(worker->flags & WORKER_NOT_RUNNING))
-		atomic_inc(get_gcwq_nr_running(cpu));
+		atomic_inc(get_pool_nr_running(worker->pool));
 }
 
 /**
@@ -692,8 +727,8 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
 				       unsigned int cpu)
 {
 	struct worker *worker = kthread_data(task), *to_wakeup = NULL;
-	struct global_cwq *gcwq = get_gcwq(cpu);
-	atomic_t *nr_running = get_gcwq_nr_running(cpu);
+	struct worker_pool *pool = worker->pool;
+	atomic_t *nr_running = get_pool_nr_running(pool);
 
 	if (worker->flags & WORKER_NOT_RUNNING)
 		return NULL;
@@ -706,14 +741,14 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
 	 * worklist not empty test sequence is in insert_work().
 	 * Please read comment there.
 	 *
-	 * NOT_RUNNING is clear.  This means that trustee is not in
-	 * charge and we're running on the local cpu w/ rq lock held
-	 * and preemption disabled, which in turn means that none else
-	 * could be manipulating idle_list, so dereferencing idle_list
-	 * without gcwq lock is safe.
+	 * NOT_RUNNING is clear.  This means that we're bound to and
+	 * running on the local cpu w/ rq lock held and preemption
+	 * disabled, which in turn means that none else could be
+	 * manipulating idle_list, so dereferencing idle_list without gcwq
+	 * lock is safe.
 	 */
-	if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
-		to_wakeup = first_worker(gcwq);
+	if (atomic_dec_and_test(nr_running) && !list_empty(&pool->worklist))
+		to_wakeup = first_worker(pool);
 	return to_wakeup ? to_wakeup->task : NULL;
 }
 
@@ -733,7 +768,7 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
 static inline void worker_set_flags(struct worker *worker, unsigned int flags,
 				    bool wakeup)
 {
-	struct global_cwq *gcwq = worker->gcwq;
+	struct worker_pool *pool = worker->pool;
 
 	WARN_ON_ONCE(worker->task != current);
 
@@ -744,12 +779,12 @@ static inline void worker_set_flags(struct worker *worker, unsigned int flags,
 	 */
 	if ((flags & WORKER_NOT_RUNNING) &&
 	    !(worker->flags & WORKER_NOT_RUNNING)) {
-		atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
+		atomic_t *nr_running = get_pool_nr_running(pool);
 
 		if (wakeup) {
 			if (atomic_dec_and_test(nr_running) &&
-			    !list_empty(&gcwq->worklist))
-				wake_up_worker(gcwq);
+			    !list_empty(&pool->worklist))
+				wake_up_worker(pool);
 		} else
 			atomic_dec(nr_running);
 	}
@@ -769,7 +804,7 @@ static inline void worker_set_flags(struct worker *worker, unsigned int flags,
  */
 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 {
-	struct global_cwq *gcwq = worker->gcwq;
+	struct worker_pool *pool = worker->pool;
 	unsigned int oflags = worker->flags;
 
 	WARN_ON_ONCE(worker->task != current);
@@ -783,7 +818,7 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 	 */
 	if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
 		if (!(worker->flags & WORKER_NOT_RUNNING))
-			atomic_inc(get_gcwq_nr_running(gcwq->cpu));
+			atomic_inc(get_pool_nr_running(pool));
 }
 
 /**
@@ -867,43 +902,6 @@ static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
 }
 
 /**
- * gcwq_determine_ins_pos - find insertion position
- * @gcwq: gcwq of interest
- * @cwq: cwq a work is being queued for
- *
- * A work for @cwq is about to be queued on @gcwq, determine insertion
- * position for the work.  If @cwq is for HIGHPRI wq, the work is
- * queued at the head of the queue but in FIFO order with respect to
- * other HIGHPRI works; otherwise, at the end of the queue.  This
- * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
- * there are HIGHPRI works pending.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock).
- *
- * RETURNS:
- * Pointer to inserstion position.
- */
-static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
-					       struct cpu_workqueue_struct *cwq)
-{
-	struct work_struct *twork;
-
-	if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
-		return &gcwq->worklist;
-
-	list_for_each_entry(twork, &gcwq->worklist, entry) {
-		struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
-
-		if (!(tcwq->wq->flags & WQ_HIGHPRI))
-			break;
-	}
-
-	gcwq->flags |= GCWQ_HIGHPRI_PENDING;
-	return &twork->entry;
-}
-
-/**
  * insert_work - insert a work into gcwq
  * @cwq: cwq @work belongs to
  * @work: work to insert
@@ -920,7 +918,7 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
 			struct work_struct *work, struct list_head *head,
 			unsigned int extra_flags)
 {
-	struct global_cwq *gcwq = cwq->gcwq;
+	struct worker_pool *pool = cwq->pool;
 
 	/* we own @work, set data and link */
 	set_work_cwq(work, cwq, extra_flags);
@@ -940,8 +938,8 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
 	 */
 	smp_mb();
 
-	if (__need_more_worker(gcwq))
-		wake_up_worker(gcwq);
+	if (__need_more_worker(pool))
+		wake_up_worker(pool);
 }
 
 /*
@@ -1043,7 +1041,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 	if (likely(cwq->nr_active < cwq->max_active)) {
 		trace_workqueue_activate_work(work);
 		cwq->nr_active++;
-		worklist = gcwq_determine_ins_pos(gcwq, cwq);
+		worklist = &cwq->pool->worklist;
 	} else {
 		work_flags |= WORK_STRUCT_DELAYED;
 		worklist = &cwq->delayed_works;
@@ -1192,7 +1190,8 @@ EXPORT_SYMBOL_GPL(queue_delayed_work_on);
  */
 static void worker_enter_idle(struct worker *worker)
 {
-	struct global_cwq *gcwq = worker->gcwq;
+	struct worker_pool *pool = worker->pool;
+	struct global_cwq *gcwq = pool->gcwq;
 
 	BUG_ON(worker->flags & WORKER_IDLE);
 	BUG_ON(!list_empty(&worker->entry) &&
@@ -1200,27 +1199,24 @@ static void worker_enter_idle(struct worker *worker)
 
 	/* can't use worker_set_flags(), also called from start_worker() */
 	worker->flags |= WORKER_IDLE;
-	gcwq->nr_idle++;
+	pool->nr_idle++;
 	worker->last_active = jiffies;
 
 	/* idle_list is LIFO */
-	list_add(&worker->entry, &gcwq->idle_list);
+	list_add(&worker->entry, &pool->idle_list);
 
-	if (likely(!(worker->flags & WORKER_ROGUE))) {
-		if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
-			mod_timer(&gcwq->idle_timer,
-				  jiffies + IDLE_WORKER_TIMEOUT);
-	} else
-		wake_up_all(&gcwq->trustee_wait);
+	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
+		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
 
 	/*
-	 * Sanity check nr_running.  Because trustee releases gcwq->lock
-	 * between setting %WORKER_ROGUE and zapping nr_running, the
-	 * warning may trigger spuriously.  Check iff trustee is idle.
+	 * Sanity check nr_running.  Because gcwq_unbind_fn() releases
+	 * gcwq->lock between setting %WORKER_UNBOUND and zapping
+	 * nr_running, the warning may trigger spuriously.  Check iff
+	 * unbind is not in progress.
 	 */
-	WARN_ON_ONCE(gcwq->trustee_state == TRUSTEE_DONE &&
-		     gcwq->nr_workers == gcwq->nr_idle &&
-		     atomic_read(get_gcwq_nr_running(gcwq->cpu)));
+	WARN_ON_ONCE(!(gcwq->flags & GCWQ_DISASSOCIATED) &&
+		     pool->nr_workers == pool->nr_idle &&
+		     atomic_read(get_pool_nr_running(pool)));
 }
 
 /**
@@ -1234,11 +1230,11 @@ static void worker_enter_idle(struct worker *worker)
  */
 static void worker_leave_idle(struct worker *worker)
 {
-	struct global_cwq *gcwq = worker->gcwq;
+	struct worker_pool *pool = worker->pool;
 
 	BUG_ON(!(worker->flags & WORKER_IDLE));
 	worker_clr_flags(worker, WORKER_IDLE);
-	gcwq->nr_idle--;
+	pool->nr_idle--;
 	list_del_init(&worker->entry);
 }
 
@@ -1258,11 +1254,11 @@ static void worker_leave_idle(struct worker *worker)
  * verbatim as it's best effort and blocking and gcwq may be
  * [dis]associated in the meantime.
  *
- * This function tries set_cpus_allowed() and locks gcwq and verifies
- * the binding against GCWQ_DISASSOCIATED which is set during
- * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
- * idle state or fetches works without dropping lock, it can guarantee
- * the scheduling requirement described in the first paragraph.
+ * This function tries set_cpus_allowed() and locks gcwq and verifies the
+ * binding against %GCWQ_DISASSOCIATED which is set during
+ * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker
+ * enters idle state or fetches works without dropping lock, it can
+ * guarantee the scheduling requirement described in the first paragraph.
  *
  * CONTEXT:
  * Might sleep.  Called without any lock but returns with gcwq->lock
@@ -1275,7 +1271,7 @@ static void worker_leave_idle(struct worker *worker)
 static bool worker_maybe_bind_and_lock(struct worker *worker)
 __acquires(&gcwq->lock)
 {
-	struct global_cwq *gcwq = worker->gcwq;
+	struct global_cwq *gcwq = worker->pool->gcwq;
 	struct task_struct *task = worker->task;
 
 	while (true) {
@@ -1308,16 +1304,40 @@ __acquires(&gcwq->lock)
 	}
 }
 
+struct idle_rebind {
+	int			cnt;		/* # workers to be rebound */
+	struct completion	done;		/* all workers rebound */
+};
+
+/*
+ * Rebind an idle @worker to its CPU.  During CPU onlining, this has to
+ * happen synchronously for idle workers.  worker_thread() will test
+ * %WORKER_REBIND before leaving idle and call this function.
+ */
+static void idle_worker_rebind(struct worker *worker)
+{
+	struct global_cwq *gcwq = worker->pool->gcwq;
+
+	/* CPU must be online at this point */
+	WARN_ON(!worker_maybe_bind_and_lock(worker));
+	if (!--worker->idle_rebind->cnt)
+		complete(&worker->idle_rebind->done);
+	spin_unlock_irq(&worker->pool->gcwq->lock);
+
+	/* we did our part, wait for rebind_workers() to finish up */
+	wait_event(gcwq->rebind_hold, !(worker->flags & WORKER_REBIND));
+}
+
 /*
- * Function for worker->rebind_work used to rebind rogue busy workers
- * to the associated cpu which is coming back online.  This is
- * scheduled by cpu up but can race with other cpu hotplug operations
- * and may be executed twice without intervening cpu down.
+ * Function for @worker->rebind.work used to rebind unbound busy workers to
+ * the associated cpu which is coming back online.  This is scheduled by
+ * cpu up but can race with other cpu hotplug operations and may be
+ * executed twice without intervening cpu down.
  */
-static void worker_rebind_fn(struct work_struct *work)
+static void busy_worker_rebind_fn(struct work_struct *work)
 {
 	struct worker *worker = container_of(work, struct worker, rebind_work);
-	struct global_cwq *gcwq = worker->gcwq;
+	struct global_cwq *gcwq = worker->pool->gcwq;
 
 	if (worker_maybe_bind_and_lock(worker))
 		worker_clr_flags(worker, WORKER_REBIND);
@@ -1325,6 +1345,112 @@ static void worker_rebind_fn(struct work_struct *work)
 	spin_unlock_irq(&gcwq->lock);
 }
 
+/**
+ * rebind_workers - rebind all workers of a gcwq to the associated CPU
+ * @gcwq: gcwq of interest
+ *
+ * @gcwq->cpu is coming online.  Rebind all workers to the CPU.  Rebinding
+ * is different for idle and busy ones.
+ *
+ * The idle ones should be rebound synchronously and idle rebinding should
+ * be complete before any worker starts executing work items with
+ * concurrency management enabled; otherwise, scheduler may oops trying to
+ * wake up non-local idle worker from wq_worker_sleeping().
+ *
+ * This is achieved by repeatedly requesting rebinding until all idle
+ * workers are known to have been rebound under @gcwq->lock and holding all
+ * idle workers from becoming busy until idle rebinding is complete.
+ *
+ * Once idle workers are rebound, busy workers can be rebound as they
+ * finish executing their current work items.  Queueing the rebind work at
+ * the head of their scheduled lists is enough.  Note that nr_running will
+ * be properbly bumped as busy workers rebind.
+ *
+ * On return, all workers are guaranteed to either be bound or have rebind
+ * work item scheduled.
+ */
+static void rebind_workers(struct global_cwq *gcwq)
+	__releases(&gcwq->lock) __acquires(&gcwq->lock)
+{
+	struct idle_rebind idle_rebind;
+	struct worker_pool *pool;
+	struct worker *worker;
+	struct hlist_node *pos;
+	int i;
+
+	lockdep_assert_held(&gcwq->lock);
+
+	for_each_worker_pool(pool, gcwq)
+		lockdep_assert_held(&pool->manager_mutex);
+
+	/*
+	 * Rebind idle workers.  Interlocked both ways.  We wait for
+	 * workers to rebind via @idle_rebind.done.  Workers will wait for
+	 * us to finish up by watching %WORKER_REBIND.
+	 */
+	init_completion(&idle_rebind.done);
+retry:
+	idle_rebind.cnt = 1;
+	INIT_COMPLETION(idle_rebind.done);
+
+	/* set REBIND and kick idle ones, we'll wait for these later */
+	for_each_worker_pool(pool, gcwq) {
+		list_for_each_entry(worker, &pool->idle_list, entry) {
+			if (worker->flags & WORKER_REBIND)
+				continue;
+
+			/* morph UNBOUND to REBIND */
+			worker->flags &= ~WORKER_UNBOUND;
+			worker->flags |= WORKER_REBIND;
+
+			idle_rebind.cnt++;
+			worker->idle_rebind = &idle_rebind;
+
+			/* worker_thread() will call idle_worker_rebind() */
+			wake_up_process(worker->task);
+		}
+	}
+
+	if (--idle_rebind.cnt) {
+		spin_unlock_irq(&gcwq->lock);
+		wait_for_completion(&idle_rebind.done);
+		spin_lock_irq(&gcwq->lock);
+		/* busy ones might have become idle while waiting, retry */
+		goto retry;
+	}
+
+	/*
+	 * All idle workers are rebound and waiting for %WORKER_REBIND to
+	 * be cleared inside idle_worker_rebind().  Clear and release.
+	 * Clearing %WORKER_REBIND from this foreign context is safe
+	 * because these workers are still guaranteed to be idle.
+	 */
+	for_each_worker_pool(pool, gcwq)
+		list_for_each_entry(worker, &pool->idle_list, entry)
+			worker->flags &= ~WORKER_REBIND;
+
+	wake_up_all(&gcwq->rebind_hold);
+
+	/* rebind busy workers */
+	for_each_busy_worker(worker, i, pos, gcwq) {
+		struct work_struct *rebind_work = &worker->rebind_work;
+
+		/* morph UNBOUND to REBIND */
+		worker->flags &= ~WORKER_UNBOUND;
+		worker->flags |= WORKER_REBIND;
+
+		if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
+				     work_data_bits(rebind_work)))
+			continue;
+
+		/* wq doesn't matter, use the default one */
+		debug_work_activate(rebind_work);
+		insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
+			    worker->scheduled.next,
+			    work_color_to_flags(WORK_NO_COLOR));
+	}
+}
+
 static struct worker *alloc_worker(void)
 {
 	struct worker *worker;
@@ -1333,7 +1459,7 @@ static struct worker *alloc_worker(void)
 	if (worker) {
 		INIT_LIST_HEAD(&worker->entry);
 		INIT_LIST_HEAD(&worker->scheduled);
-		INIT_WORK(&worker->rebind_work, worker_rebind_fn);
+		INIT_WORK(&worker->rebind_work, busy_worker_rebind_fn);
 		/* on creation a worker is in !idle && prep state */
 		worker->flags = WORKER_PREP;
 	}
@@ -1342,10 +1468,9 @@ static struct worker *alloc_worker(void)
 
 /**
  * create_worker - create a new workqueue worker
- * @gcwq: gcwq the new worker will belong to
- * @bind: whether to set affinity to @cpu or not
+ * @pool: pool the new worker will belong to
  *
- * Create a new worker which is bound to @gcwq.  The returned worker
+ * Create a new worker which is bound to @pool.  The returned worker
  * can be started by calling start_worker() or destroyed using
  * destroy_worker().
  *
@@ -1355,16 +1480,17 @@ static struct worker *alloc_worker(void)
  * RETURNS:
  * Pointer to the newly created worker.
  */
-static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
+static struct worker *create_worker(struct worker_pool *pool)
 {
-	bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
+	struct global_cwq *gcwq = pool->gcwq;
+	const char *pri = worker_pool_pri(pool) ? "H" : "";
 	struct worker *worker = NULL;
 	int id = -1;
 
 	spin_lock_irq(&gcwq->lock);
-	while (ida_get_new(&gcwq->worker_ida, &id)) {
+	while (ida_get_new(&pool->worker_ida, &id)) {
 		spin_unlock_irq(&gcwq->lock);
-		if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
+		if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL))
 			goto fail;
 		spin_lock_irq(&gcwq->lock);
 	}
@@ -1374,38 +1500,43 @@ static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
 	if (!worker)
 		goto fail;
 
-	worker->gcwq = gcwq;
+	worker->pool = pool;
 	worker->id = id;
 
-	if (!on_unbound_cpu)
+	if (gcwq->cpu != WORK_CPU_UNBOUND)
 		worker->task = kthread_create_on_node(worker_thread,
-						      worker,
-						      cpu_to_node(gcwq->cpu),
-						      "kworker/%u:%d", gcwq->cpu, id);
+					worker, cpu_to_node(gcwq->cpu),
+					"kworker/%u:%d%s", gcwq->cpu, id, pri);
 	else
 		worker->task = kthread_create(worker_thread, worker,
-					      "kworker/u:%d", id);
+					      "kworker/u:%d%s", id, pri);
 	if (IS_ERR(worker->task))
 		goto fail;
 
+	if (worker_pool_pri(pool))
+		set_user_nice(worker->task, HIGHPRI_NICE_LEVEL);
+
 	/*
-	 * A rogue worker will become a regular one if CPU comes
-	 * online later on.  Make sure every worker has
-	 * PF_THREAD_BOUND set.
+	 * Determine CPU binding of the new worker depending on
+	 * %GCWQ_DISASSOCIATED.  The caller is responsible for ensuring the
+	 * flag remains stable across this function.  See the comments
+	 * above the flag definition for details.
+	 *
+	 * As an unbound worker may later become a regular one if CPU comes
+	 * online, make sure every worker has %PF_THREAD_BOUND set.
 	 */
-	if (bind && !on_unbound_cpu)
+	if (!(gcwq->flags & GCWQ_DISASSOCIATED)) {
 		kthread_bind(worker->task, gcwq->cpu);
-	else {
+	} else {
 		worker->task->flags |= PF_THREAD_BOUND;
-		if (on_unbound_cpu)
-			worker->flags |= WORKER_UNBOUND;
+		worker->flags |= WORKER_UNBOUND;
 	}
 
 	return worker;
 fail:
 	if (id >= 0) {
 		spin_lock_irq(&gcwq->lock);
-		ida_remove(&gcwq->worker_ida, id);
+		ida_remove(&pool->worker_ida, id);
 		spin_unlock_irq(&gcwq->lock);
 	}
 	kfree(worker);
@@ -1424,7 +1555,7 @@ fail:
 static void start_worker(struct worker *worker)
 {
 	worker->flags |= WORKER_STARTED;
-	worker->gcwq->nr_workers++;
+	worker->pool->nr_workers++;
 	worker_enter_idle(worker);
 	wake_up_process(worker->task);
 }
@@ -1440,7 +1571,8 @@ static void start_worker(struct worker *worker)
  */
 static void destroy_worker(struct worker *worker)
 {
-	struct global_cwq *gcwq = worker->gcwq;
+	struct worker_pool *pool = worker->pool;
+	struct global_cwq *gcwq = pool->gcwq;
 	int id = worker->id;
 
 	/* sanity check frenzy */
@@ -1448,9 +1580,9 @@ static void destroy_worker(struct worker *worker)
 	BUG_ON(!list_empty(&worker->scheduled));
 
 	if (worker->flags & WORKER_STARTED)
-		gcwq->nr_workers--;
+		pool->nr_workers--;
 	if (worker->flags & WORKER_IDLE)
-		gcwq->nr_idle--;
+		pool->nr_idle--;
 
 	list_del_init(&worker->entry);
 	worker->flags |= WORKER_DIE;
@@ -1461,29 +1593,30 @@ static void destroy_worker(struct worker *worker)
 	kfree(worker);
 
 	spin_lock_irq(&gcwq->lock);
-	ida_remove(&gcwq->worker_ida, id);
+	ida_remove(&pool->worker_ida, id);
 }
 
-static void idle_worker_timeout(unsigned long __gcwq)
+static void idle_worker_timeout(unsigned long __pool)
 {
-	struct global_cwq *gcwq = (void *)__gcwq;
+	struct worker_pool *pool = (void *)__pool;
+	struct global_cwq *gcwq = pool->gcwq;
 
 	spin_lock_irq(&gcwq->lock);
 
-	if (too_many_workers(gcwq)) {
+	if (too_many_workers(pool)) {
 		struct worker *worker;
 		unsigned long expires;
 
 		/* idle_list is kept in LIFO order, check the last one */
-		worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
+		worker = list_entry(pool->idle_list.prev, struct worker, entry);
 		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
 
 		if (time_before(jiffies, expires))
-			mod_timer(&gcwq->idle_timer, expires);
+			mod_timer(&pool->idle_timer, expires);
 		else {
 			/* it's been idle for too long, wake up manager */
-			gcwq->flags |= GCWQ_MANAGE_WORKERS;
-			wake_up_worker(gcwq);
+			pool->flags |= POOL_MANAGE_WORKERS;
+			wake_up_worker(pool);
 		}
 	}
 
@@ -1500,7 +1633,7 @@ static bool send_mayday(struct work_struct *work)
 		return false;
 
 	/* mayday mayday mayday */
-	cpu = cwq->gcwq->cpu;
+	cpu = cwq->pool->gcwq->cpu;
 	/* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
 	if (cpu == WORK_CPU_UNBOUND)
 		cpu = 0;
@@ -1509,37 +1642,38 @@ static bool send_mayday(struct work_struct *work)
 	return true;
 }
 
-static void gcwq_mayday_timeout(unsigned long __gcwq)
+static void gcwq_mayday_timeout(unsigned long __pool)
 {
-	struct global_cwq *gcwq = (void *)__gcwq;
+	struct worker_pool *pool = (void *)__pool;
+	struct global_cwq *gcwq = pool->gcwq;
 	struct work_struct *work;
 
 	spin_lock_irq(&gcwq->lock);
 
-	if (need_to_create_worker(gcwq)) {
+	if (need_to_create_worker(pool)) {
 		/*
 		 * We've been trying to create a new worker but
 		 * haven't been successful.  We might be hitting an
 		 * allocation deadlock.  Send distress signals to
 		 * rescuers.
 		 */
-		list_for_each_entry(work, &gcwq->worklist, entry)
+		list_for_each_entry(work, &pool->worklist, entry)
 			send_mayday(work);
 	}
 
 	spin_unlock_irq(&gcwq->lock);
 
-	mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
+	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
 }
 
 /**
  * maybe_create_worker - create a new worker if necessary
- * @gcwq: gcwq to create a new worker for
+ * @pool: pool to create a new worker for
  *
- * Create a new worker for @gcwq if necessary.  @gcwq is guaranteed to
+ * Create a new worker for @pool if necessary.  @pool is guaranteed to
  * have at least one idle worker on return from this function.  If
  * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
- * sent to all rescuers with works scheduled on @gcwq to resolve
+ * sent to all rescuers with works scheduled on @pool to resolve
  * possible allocation deadlock.
  *
  * On return, need_to_create_worker() is guaranteed to be false and
@@ -1554,52 +1688,54 @@ static void gcwq_mayday_timeout(unsigned long __gcwq)
  * false if no action was taken and gcwq->lock stayed locked, true
  * otherwise.
  */
-static bool maybe_create_worker(struct global_cwq *gcwq)
+static bool maybe_create_worker(struct worker_pool *pool)
 __releases(&gcwq->lock)
 __acquires(&gcwq->lock)
 {
-	if (!need_to_create_worker(gcwq))
+	struct global_cwq *gcwq = pool->gcwq;
+
+	if (!need_to_create_worker(pool))
 		return false;
 restart:
 	spin_unlock_irq(&gcwq->lock);
 
 	/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
-	mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
+	mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
 
 	while (true) {
 		struct worker *worker;
 
-		worker = create_worker(gcwq, true);
+		worker = create_worker(pool);
 		if (worker) {
-			del_timer_sync(&gcwq->mayday_timer);
+			del_timer_sync(&pool->mayday_timer);
 			spin_lock_irq(&gcwq->lock);
 			start_worker(worker);
-			BUG_ON(need_to_create_worker(gcwq));
+			BUG_ON(need_to_create_worker(pool));
 			return true;
 		}
 
-		if (!need_to_create_worker(gcwq))
+		if (!need_to_create_worker(pool))
 			break;
 
 		__set_current_state(TASK_INTERRUPTIBLE);
 		schedule_timeout(CREATE_COOLDOWN);
 
-		if (!need_to_create_worker(gcwq))
+		if (!need_to_create_worker(pool))
 			break;
 	}
 
-	del_timer_sync(&gcwq->mayday_timer);
+	del_timer_sync(&pool->mayday_timer);
 	spin_lock_irq(&gcwq->lock);
-	if (need_to_create_worker(gcwq))
+	if (need_to_create_worker(pool))
 		goto restart;
 	return true;
 }
 
 /**
  * maybe_destroy_worker - destroy workers which have been idle for a while
- * @gcwq: gcwq to destroy workers for
+ * @pool: pool to destroy workers for
  *
- * Destroy @gcwq workers which have been idle for longer than
+ * Destroy @pool workers which have been idle for longer than
  * IDLE_WORKER_TIMEOUT.
  *
  * LOCKING:
@@ -1610,19 +1746,19 @@ restart:
  * false if no action was taken and gcwq->lock stayed locked, true
  * otherwise.
  */
-static bool maybe_destroy_workers(struct global_cwq *gcwq)
+static bool maybe_destroy_workers(struct worker_pool *pool)
 {
 	bool ret = false;
 
-	while (too_many_workers(gcwq)) {
+	while (too_many_workers(pool)) {
 		struct worker *worker;
 		unsigned long expires;
 
-		worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
+		worker = list_entry(pool->idle_list.prev, struct worker, entry);
 		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
 
 		if (time_before(jiffies, expires)) {
-			mod_timer(&gcwq->idle_timer, expires);
+			mod_timer(&pool->idle_timer, expires);
 			break;
 		}
 
@@ -1655,31 +1791,22 @@ static bool maybe_destroy_workers(struct global_cwq *gcwq)
  */
 static bool manage_workers(struct worker *worker)
 {
-	struct global_cwq *gcwq = worker->gcwq;
+	struct worker_pool *pool = worker->pool;
 	bool ret = false;
 
-	if (gcwq->flags & GCWQ_MANAGING_WORKERS)
+	if (!mutex_trylock(&pool->manager_mutex))
 		return ret;
 
-	gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
-	gcwq->flags |= GCWQ_MANAGING_WORKERS;
+	pool->flags &= ~POOL_MANAGE_WORKERS;
 
 	/*
 	 * Destroy and then create so that may_start_working() is true
 	 * on return.
 	 */
-	ret |= maybe_destroy_workers(gcwq);
-	ret |= maybe_create_worker(gcwq);
-
-	gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
-
-	/*
-	 * The trustee might be waiting to take over the manager
-	 * position, tell it we're done.
-	 */
-	if (unlikely(gcwq->trustee))
-		wake_up_all(&gcwq->trustee_wait);
+	ret |= maybe_destroy_workers(pool);
+	ret |= maybe_create_worker(pool);
 
+	mutex_unlock(&pool->manager_mutex);
 	return ret;
 }
 
@@ -1728,10 +1855,9 @@ 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);
-	struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
 
 	trace_workqueue_activate_work(work);
-	move_linked_works(work, pos, NULL);
+	move_linked_works(work, &cwq->pool->worklist, NULL);
 	__clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
 	cwq->nr_active++;
 }
@@ -1804,7 +1930,8 @@ __releases(&gcwq->lock)
 __acquires(&gcwq->lock)
 {
 	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
-	struct global_cwq *gcwq = cwq->gcwq;
+	struct worker_pool *pool = worker->pool;
+	struct global_cwq *gcwq = pool->gcwq;
 	struct hlist_head *bwh = busy_worker_head(gcwq, work);
 	bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
 	work_func_t f = work->func;
@@ -1823,6 +1950,15 @@ __acquires(&gcwq->lock)
 	lockdep_copy_map(&lockdep_map, &work->lockdep_map);
 #endif
 	/*
+	 * Ensure we're on the correct CPU.  DISASSOCIATED test is
+	 * necessary to avoid spurious warnings from rescuers servicing the
+	 * unbound or a disassociated gcwq.
+	 */
+	WARN_ON_ONCE(!(worker->flags & (WORKER_UNBOUND | WORKER_REBIND)) &&
+		     !(gcwq->flags & GCWQ_DISASSOCIATED) &&
+		     raw_smp_processor_id() != gcwq->cpu);
+
+	/*
 	 * 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
@@ -1846,27 +1982,19 @@ __acquires(&gcwq->lock)
 	list_del_init(&work->entry);
 
 	/*
-	 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
-	 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
-	 */
-	if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
-		struct work_struct *nwork = list_first_entry(&gcwq->worklist,
-						struct work_struct, entry);
-
-		if (!list_empty(&gcwq->worklist) &&
-		    get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
-			wake_up_worker(gcwq);
-		else
-			gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
-	}
-
-	/*
 	 * CPU intensive works don't participate in concurrency
 	 * management.  They're the scheduler's responsibility.
 	 */
 	if (unlikely(cpu_intensive))
 		worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
 
+	/*
+	 * Unbound gcwq isn't concurrency managed and work items should be
+	 * executed ASAP.  Wake up another worker if necessary.
+	 */
+	if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool))
+		wake_up_worker(pool);
+
 	spin_unlock_irq(&gcwq->lock);
 
 	work_clear_pending(work);
@@ -1939,28 +2067,38 @@ static void process_scheduled_works(struct worker *worker)
 static int worker_thread(void *__worker)
 {
 	struct worker *worker = __worker;
-	struct global_cwq *gcwq = worker->gcwq;
+	struct worker_pool *pool = worker->pool;
+	struct global_cwq *gcwq = pool->gcwq;
 
 	/* tell the scheduler that this is a workqueue worker */
 	worker->task->flags |= PF_WQ_WORKER;
 woke_up:
 	spin_lock_irq(&gcwq->lock);
 
-	/* DIE can be set only while we're idle, checking here is enough */
-	if (worker->flags & WORKER_DIE) {
+	/*
+	 * DIE can be set only while idle and REBIND set while busy has
+	 * @worker->rebind_work scheduled.  Checking here is enough.
+	 */
+	if (unlikely(worker->flags & (WORKER_REBIND | WORKER_DIE))) {
 		spin_unlock_irq(&gcwq->lock);
-		worker->task->flags &= ~PF_WQ_WORKER;
-		return 0;
+
+		if (worker->flags & WORKER_DIE) {
+			worker->task->flags &= ~PF_WQ_WORKER;
+			return 0;
+		}
+
+		idle_worker_rebind(worker);
+		goto woke_up;
 	}
 
 	worker_leave_idle(worker);
 recheck:
 	/* no more worker necessary? */
-	if (!need_more_worker(gcwq))
+	if (!need_more_worker(pool))
 		goto sleep;
 
 	/* do we need to manage? */
-	if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
+	if (unlikely(!may_start_working(pool)) && manage_workers(worker))
 		goto recheck;
 
 	/*
@@ -1979,7 +2117,7 @@ recheck:
 
 	do {
 		struct work_struct *work =
-			list_first_entry(&gcwq->worklist,
+			list_first_entry(&pool->worklist,
 					 struct work_struct, entry);
 
 		if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
@@ -1991,11 +2129,11 @@ recheck:
 			move_linked_works(work, &worker->scheduled, NULL);
 			process_scheduled_works(worker);
 		}
-	} while (keep_working(gcwq));
+	} while (keep_working(pool));
 
 	worker_set_flags(worker, WORKER_PREP, false);
 sleep:
-	if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
+	if (unlikely(need_to_manage_workers(pool)) && manage_workers(worker))
 		goto recheck;
 
 	/*
@@ -2053,14 +2191,15 @@ repeat:
 	for_each_mayday_cpu(cpu, wq->mayday_mask) {
 		unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
 		struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
-		struct global_cwq *gcwq = cwq->gcwq;
+		struct worker_pool *pool = cwq->pool;
+		struct global_cwq *gcwq = pool->gcwq;
 		struct work_struct *work, *n;
 
 		__set_current_state(TASK_RUNNING);
 		mayday_clear_cpu(cpu, wq->mayday_mask);
 
 		/* migrate to the target cpu if possible */
-		rescuer->gcwq = gcwq;
+		rescuer->pool = pool;
 		worker_maybe_bind_and_lock(rescuer);
 
 		/*
@@ -2068,7 +2207,7 @@ repeat:
 		 * process'em.
 		 */
 		BUG_ON(!list_empty(&rescuer->scheduled));
-		list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
+		list_for_each_entry_safe(work, n, &pool->worklist, entry)
 			if (get_work_cwq(work) == cwq)
 				move_linked_works(work, scheduled, &n);
 
@@ -2079,8 +2218,8 @@ repeat:
 		 * regular worker; otherwise, we end up with 0 concurrency
 		 * and stalling the execution.
 		 */
-		if (keep_working(gcwq))
-			wake_up_worker(gcwq);
+		if (keep_working(pool))
+			wake_up_worker(pool);
 
 		spin_unlock_irq(&gcwq->lock);
 	}
@@ -2205,7 +2344,7 @@ static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
 
 	for_each_cwq_cpu(cpu, wq) {
 		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
-		struct global_cwq *gcwq = cwq->gcwq;
+		struct global_cwq *gcwq = cwq->pool->gcwq;
 
 		spin_lock_irq(&gcwq->lock);
 
@@ -2421,9 +2560,9 @@ reflush:
 		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 		bool drained;
 
-		spin_lock_irq(&cwq->gcwq->lock);
+		spin_lock_irq(&cwq->pool->gcwq->lock);
 		drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
-		spin_unlock_irq(&cwq->gcwq->lock);
+		spin_unlock_irq(&cwq->pool->gcwq->lock);
 
 		if (drained)
 			continue;
@@ -2463,7 +2602,7 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
 		 */
 		smp_rmb();
 		cwq = get_work_cwq(work);
-		if (unlikely(!cwq || gcwq != cwq->gcwq))
+		if (unlikely(!cwq || gcwq != cwq->pool->gcwq))
 			goto already_gone;
 	} else if (wait_executing) {
 		worker = find_worker_executing_work(gcwq, work);
@@ -2984,13 +3123,6 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
 	if (flags & WQ_MEM_RECLAIM)
 		flags |= WQ_RESCUER;
 
-	/*
-	 * Unbound workqueues aren't concurrency managed and should be
-	 * dispatched to workers immediately.
-	 */
-	if (flags & WQ_UNBOUND)
-		flags |= WQ_HIGHPRI;
-
 	max_active = max_active ?: WQ_DFL_ACTIVE;
 	max_active = wq_clamp_max_active(max_active, flags, wq->name);
 
@@ -3011,9 +3143,10 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
 	for_each_cwq_cpu(cpu, wq) {
 		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 		struct global_cwq *gcwq = get_gcwq(cpu);
+		int pool_idx = (bool)(flags & WQ_HIGHPRI);
 
 		BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
-		cwq->gcwq = gcwq;
+		cwq->pool = &gcwq->pools[pool_idx];
 		cwq->wq = wq;
 		cwq->flush_color = -1;
 		cwq->max_active = max_active;
@@ -3225,369 +3358,143 @@ EXPORT_SYMBOL_GPL(work_busy);
  * gcwqs serve mix of short, long and very long running works making
  * blocked draining impractical.
  *
- * This is solved by allowing a gcwq to be detached from CPU, running
- * it with unbound (rogue) workers and allowing it to be reattached
- * later if the cpu comes back online.  A separate thread is created
- * to govern a gcwq in such state and is called the trustee of the
- * gcwq.
- *
- * Trustee states and their descriptions.
- *
- * START	Command state used on startup.  On CPU_DOWN_PREPARE, a
- *		new trustee is started with this state.
- *
- * IN_CHARGE	Once started, trustee will enter this state after
- *		assuming the manager role and making all existing
- *		workers rogue.  DOWN_PREPARE waits for trustee to
- *		enter this state.  After reaching IN_CHARGE, trustee
- *		tries to execute the pending worklist until it's empty
- *		and the state is set to BUTCHER, or the state is set
- *		to RELEASE.
- *
- * BUTCHER	Command state which is set by the cpu callback after
- *		the cpu has went down.  Once this state is set trustee
- *		knows that there will be no new works on the worklist
- *		and once the worklist is empty it can proceed to
- *		killing idle workers.
- *
- * RELEASE	Command state which is set by the cpu callback if the
- *		cpu down has been canceled or it has come online
- *		again.  After recognizing this state, trustee stops
- *		trying to drain or butcher and clears ROGUE, rebinds
- *		all remaining workers back to the cpu and releases
- *		manager role.
- *
- * DONE		Trustee will enter this state after BUTCHER or RELEASE
- *		is complete.
- *
- *          trustee                 CPU                draining
- *         took over                down               complete
- * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
- *                        |                     |                  ^
- *                        | CPU is back online  v   return workers |
- *                         ----------------> RELEASE --------------
+ * This is solved by allowing a gcwq to be disassociated from the CPU
+ * running as an unbound one and allowing it to be reattached later if the
+ * cpu comes back online.
  */
 
-/**
- * trustee_wait_event_timeout - timed event wait for trustee
- * @cond: condition to wait for
- * @timeout: timeout in jiffies
- *
- * wait_event_timeout() for trustee to use.  Handles locking and
- * checks for RELEASE request.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock) which may be released and regrabbed
- * multiple times.  To be used by trustee.
- *
- * RETURNS:
- * Positive indicating left time if @cond is satisfied, 0 if timed
- * out, -1 if canceled.
- */
-#define trustee_wait_event_timeout(cond, timeout) ({			\
-	long __ret = (timeout);						\
-	while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) &&	\
-	       __ret) {							\
-		spin_unlock_irq(&gcwq->lock);				\
-		__wait_event_timeout(gcwq->trustee_wait, (cond) ||	\
-			(gcwq->trustee_state == TRUSTEE_RELEASE),	\
-			__ret);						\
-		spin_lock_irq(&gcwq->lock);				\
-	}								\
-	gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret);		\
-})
-
-/**
- * trustee_wait_event - event wait for trustee
- * @cond: condition to wait for
- *
- * wait_event() for trustee to use.  Automatically handles locking and
- * checks for CANCEL request.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock) which may be released and regrabbed
- * multiple times.  To be used by trustee.
- *
- * RETURNS:
- * 0 if @cond is satisfied, -1 if canceled.
- */
-#define trustee_wait_event(cond) ({					\
-	long __ret1;							\
-	__ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
-	__ret1 < 0 ? -1 : 0;						\
-})
-
-static int __cpuinit trustee_thread(void *__gcwq)
+/* claim manager positions of all pools */
+static void gcwq_claim_management_and_lock(struct global_cwq *gcwq)
 {
-	struct global_cwq *gcwq = __gcwq;
-	struct worker *worker;
-	struct work_struct *work;
-	struct hlist_node *pos;
-	long rc;
-	int i;
-
-	BUG_ON(gcwq->cpu != smp_processor_id());
+	struct worker_pool *pool;
 
+	for_each_worker_pool(pool, gcwq)
+		mutex_lock_nested(&pool->manager_mutex, pool - gcwq->pools);
 	spin_lock_irq(&gcwq->lock);
-	/*
-	 * Claim the manager position and make all workers rogue.
-	 * Trustee must be bound to the target cpu and can't be
-	 * cancelled.
-	 */
-	BUG_ON(gcwq->cpu != smp_processor_id());
-	rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
-	BUG_ON(rc < 0);
-
-	gcwq->flags |= GCWQ_MANAGING_WORKERS;
-
-	list_for_each_entry(worker, &gcwq->idle_list, entry)
-		worker->flags |= WORKER_ROGUE;
+}
 
-	for_each_busy_worker(worker, i, pos, gcwq)
-		worker->flags |= WORKER_ROGUE;
+/* release manager positions */
+static void gcwq_release_management_and_unlock(struct global_cwq *gcwq)
+{
+	struct worker_pool *pool;
 
-	/*
-	 * Call schedule() so that we cross rq->lock and thus can
-	 * guarantee sched callbacks see the rogue flag.  This is
-	 * necessary as scheduler callbacks may be invoked from other
-	 * cpus.
-	 */
 	spin_unlock_irq(&gcwq->lock);
-	schedule();
-	spin_lock_irq(&gcwq->lock);
+	for_each_worker_pool(pool, gcwq)
+		mutex_unlock(&pool->manager_mutex);
+}
 
-	/*
-	 * Sched callbacks are disabled now.  Zap nr_running.  After
-	 * this, nr_running stays zero and need_more_worker() and
-	 * keep_working() are always true as long as the worklist is
-	 * not empty.
-	 */
-	atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
+static void gcwq_unbind_fn(struct work_struct *work)
+{
+	struct global_cwq *gcwq = get_gcwq(smp_processor_id());
+	struct worker_pool *pool;
+	struct worker *worker;
+	struct hlist_node *pos;
+	int i;
 
-	spin_unlock_irq(&gcwq->lock);
-	del_timer_sync(&gcwq->idle_timer);
-	spin_lock_irq(&gcwq->lock);
+	BUG_ON(gcwq->cpu != smp_processor_id());
 
-	/*
-	 * We're now in charge.  Notify and proceed to drain.  We need
-	 * to keep the gcwq running during the whole CPU down
-	 * procedure as other cpu hotunplug callbacks may need to
-	 * flush currently running tasks.
-	 */
-	gcwq->trustee_state = TRUSTEE_IN_CHARGE;
-	wake_up_all(&gcwq->trustee_wait);
+	gcwq_claim_management_and_lock(gcwq);
 
 	/*
-	 * The original cpu is in the process of dying and may go away
-	 * anytime now.  When that happens, we and all workers would
-	 * be migrated to other cpus.  Try draining any left work.  We
-	 * want to get it over with ASAP - spam rescuers, wake up as
-	 * many idlers as necessary and create new ones till the
-	 * worklist is empty.  Note that if the gcwq is frozen, there
-	 * may be frozen works in freezable cwqs.  Don't declare
-	 * completion while frozen.
+	 * We've claimed all manager positions.  Make all workers unbound
+	 * and set DISASSOCIATED.  Before this, all workers except for the
+	 * ones which are still executing works from before the last CPU
+	 * down must be on the cpu.  After this, they may become diasporas.
 	 */
-	while (gcwq->nr_workers != gcwq->nr_idle ||
-	       gcwq->flags & GCWQ_FREEZING ||
-	       gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
-		int nr_works = 0;
-
-		list_for_each_entry(work, &gcwq->worklist, entry) {
-			send_mayday(work);
-			nr_works++;
-		}
+	for_each_worker_pool(pool, gcwq)
+		list_for_each_entry(worker, &pool->idle_list, entry)
+			worker->flags |= WORKER_UNBOUND;
 
-		list_for_each_entry(worker, &gcwq->idle_list, entry) {
-			if (!nr_works--)
-				break;
-			wake_up_process(worker->task);
-		}
+	for_each_busy_worker(worker, i, pos, gcwq)
+		worker->flags |= WORKER_UNBOUND;
 
-		if (need_to_create_worker(gcwq)) {
-			spin_unlock_irq(&gcwq->lock);
-			worker = create_worker(gcwq, false);
-			spin_lock_irq(&gcwq->lock);
-			if (worker) {
-				worker->flags |= WORKER_ROGUE;
-				start_worker(worker);
-			}
-		}
+	gcwq->flags |= GCWQ_DISASSOCIATED;
 
-		/* give a breather */
-		if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
-			break;
-	}
+	gcwq_release_management_and_unlock(gcwq);
 
 	/*
-	 * Either all works have been scheduled and cpu is down, or
-	 * cpu down has already been canceled.  Wait for and butcher
-	 * all workers till we're canceled.
+	 * Call schedule() so that we cross rq->lock and thus can guarantee
+	 * sched callbacks see the %WORKER_UNBOUND flag.  This is necessary
+	 * as scheduler callbacks may be invoked from other cpus.
 	 */
-	do {
-		rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
-		while (!list_empty(&gcwq->idle_list))
-			destroy_worker(list_first_entry(&gcwq->idle_list,
-							struct worker, entry));
-	} while (gcwq->nr_workers && rc >= 0);
+	schedule();
 
 	/*
-	 * At this point, either draining has completed and no worker
-	 * is left, or cpu down has been canceled or the cpu is being
-	 * brought back up.  There shouldn't be any idle one left.
-	 * Tell the remaining busy ones to rebind once it finishes the
-	 * currently scheduled works by scheduling the rebind_work.
+	 * Sched callbacks are disabled now.  Zap nr_running.  After this,
+	 * nr_running stays zero and need_more_worker() and keep_working()
+	 * are always true as long as the worklist is not empty.  @gcwq now
+	 * behaves as unbound (in terms of concurrency management) gcwq
+	 * which is served by workers tied to the CPU.
+	 *
+	 * On return from this function, the current worker would trigger
+	 * unbound chain execution of pending work items if other workers
+	 * didn't already.
 	 */
-	WARN_ON(!list_empty(&gcwq->idle_list));
-
-	for_each_busy_worker(worker, i, pos, gcwq) {
-		struct work_struct *rebind_work = &worker->rebind_work;
-
-		/*
-		 * Rebind_work may race with future cpu hotplug
-		 * operations.  Use a separate flag to mark that
-		 * rebinding is scheduled.
-		 */
-		worker->flags |= WORKER_REBIND;
-		worker->flags &= ~WORKER_ROGUE;
-
-		/* queue rebind_work, wq doesn't matter, use the default one */
-		if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
-				     work_data_bits(rebind_work)))
-			continue;
-
-		debug_work_activate(rebind_work);
-		insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
-			    worker->scheduled.next,
-			    work_color_to_flags(WORK_NO_COLOR));
-	}
-
-	/* relinquish manager role */
-	gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
-
-	/* notify completion */
-	gcwq->trustee = NULL;
-	gcwq->trustee_state = TRUSTEE_DONE;
-	wake_up_all(&gcwq->trustee_wait);
-	spin_unlock_irq(&gcwq->lock);
-	return 0;
+	for_each_worker_pool(pool, gcwq)
+		atomic_set(get_pool_nr_running(pool), 0);
 }
 
-/**
- * wait_trustee_state - wait for trustee to enter the specified state
- * @gcwq: gcwq the trustee of interest belongs to
- * @state: target state to wait for
- *
- * Wait for the trustee to reach @state.  DONE is already matched.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock) which may be released and regrabbed
- * multiple times.  To be used by cpu_callback.
+/*
+ * Workqueues should be brought up before normal priority CPU notifiers.
+ * This will be registered high priority CPU notifier.
  */
-static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
-__releases(&gcwq->lock)
-__acquires(&gcwq->lock)
-{
-	if (!(gcwq->trustee_state == state ||
-	      gcwq->trustee_state == TRUSTEE_DONE)) {
-		spin_unlock_irq(&gcwq->lock);
-		__wait_event(gcwq->trustee_wait,
-			     gcwq->trustee_state == state ||
-			     gcwq->trustee_state == TRUSTEE_DONE);
-		spin_lock_irq(&gcwq->lock);
-	}
-}
-
-static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
-						unsigned long action,
-						void *hcpu)
+static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,
+					       unsigned long action,
+					       void *hcpu)
 {
 	unsigned int cpu = (unsigned long)hcpu;
 	struct global_cwq *gcwq = get_gcwq(cpu);
-	struct task_struct *new_trustee = NULL;
-	struct worker *uninitialized_var(new_worker);
-	unsigned long flags;
-
-	action &= ~CPU_TASKS_FROZEN;
+	struct worker_pool *pool;
 
-	switch (action) {
-	case CPU_DOWN_PREPARE:
-		new_trustee = kthread_create(trustee_thread, gcwq,
-					     "workqueue_trustee/%d\n", cpu);
-		if (IS_ERR(new_trustee))
-			return notifier_from_errno(PTR_ERR(new_trustee));
-		kthread_bind(new_trustee, cpu);
-		/* fall through */
+	switch (action & ~CPU_TASKS_FROZEN) {
 	case CPU_UP_PREPARE:
-		BUG_ON(gcwq->first_idle);
-		new_worker = create_worker(gcwq, false);
-		if (!new_worker) {
-			if (new_trustee)
-				kthread_stop(new_trustee);
-			return NOTIFY_BAD;
-		}
-	}
-
-	/* some are called w/ irq disabled, don't disturb irq status */
-	spin_lock_irqsave(&gcwq->lock, flags);
+		for_each_worker_pool(pool, gcwq) {
+			struct worker *worker;
 
-	switch (action) {
-	case CPU_DOWN_PREPARE:
-		/* initialize trustee and tell it to acquire the gcwq */
-		BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
-		gcwq->trustee = new_trustee;
-		gcwq->trustee_state = TRUSTEE_START;
-		wake_up_process(gcwq->trustee);
-		wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
-		/* fall through */
-	case CPU_UP_PREPARE:
-		BUG_ON(gcwq->first_idle);
-		gcwq->first_idle = new_worker;
-		break;
+			if (pool->nr_workers)
+				continue;
 
-	case CPU_DYING:
-		/*
-		 * Before this, the trustee and all workers except for
-		 * the ones which are still executing works from
-		 * before the last CPU down must be on the cpu.  After
-		 * this, they'll all be diasporas.
-		 */
-		gcwq->flags |= GCWQ_DISASSOCIATED;
-		break;
+			worker = create_worker(pool);
+			if (!worker)
+				return NOTIFY_BAD;
 
-	case CPU_POST_DEAD:
-		gcwq->trustee_state = TRUSTEE_BUTCHER;
-		/* fall through */
-	case CPU_UP_CANCELED:
-		destroy_worker(gcwq->first_idle);
-		gcwq->first_idle = NULL;
+			spin_lock_irq(&gcwq->lock);
+			start_worker(worker);
+			spin_unlock_irq(&gcwq->lock);
+		}
 		break;
 
 	case CPU_DOWN_FAILED:
 	case CPU_ONLINE:
+		gcwq_claim_management_and_lock(gcwq);
 		gcwq->flags &= ~GCWQ_DISASSOCIATED;
-		if (gcwq->trustee_state != TRUSTEE_DONE) {
-			gcwq->trustee_state = TRUSTEE_RELEASE;
-			wake_up_process(gcwq->trustee);
-			wait_trustee_state(gcwq, TRUSTEE_DONE);
-		}
-
-		/*
-		 * Trustee is done and there might be no worker left.
-		 * Put the first_idle in and request a real manager to
-		 * take a look.
-		 */
-		spin_unlock_irq(&gcwq->lock);
-		kthread_bind(gcwq->first_idle->task, cpu);
-		spin_lock_irq(&gcwq->lock);
-		gcwq->flags |= GCWQ_MANAGE_WORKERS;
-		start_worker(gcwq->first_idle);
-		gcwq->first_idle = NULL;
+		rebind_workers(gcwq);
+		gcwq_release_management_and_unlock(gcwq);
 		break;
 	}
+	return NOTIFY_OK;
+}
 
-	spin_unlock_irqrestore(&gcwq->lock, flags);
+/*
+ * Workqueues should be brought down after normal priority CPU notifiers.
+ * This will be registered as low priority CPU notifier.
+ */
+static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb,
+						 unsigned long action,
+						 void *hcpu)
+{
+	unsigned int cpu = (unsigned long)hcpu;
+	struct work_struct unbind_work;
 
-	return notifier_from_errno(0);
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_DOWN_PREPARE:
+		/* unbinding should happen on the local CPU */
+		INIT_WORK_ONSTACK(&unbind_work, gcwq_unbind_fn);
+		schedule_work_on(cpu, &unbind_work);
+		flush_work(&unbind_work);
+		break;
+	}
+	return NOTIFY_OK;
 }
 
 #ifdef CONFIG_SMP
@@ -3746,6 +3653,7 @@ void thaw_workqueues(void)
 
 	for_each_gcwq_cpu(cpu) {
 		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct worker_pool *pool;
 		struct workqueue_struct *wq;
 
 		spin_lock_irq(&gcwq->lock);
@@ -3767,7 +3675,8 @@ void thaw_workqueues(void)
 				cwq_activate_first_delayed(cwq);
 		}
 
-		wake_up_worker(gcwq);
+		for_each_worker_pool(pool, gcwq)
+			wake_up_worker(pool);
 
 		spin_unlock_irq(&gcwq->lock);
 	}
@@ -3783,46 +3692,57 @@ static int __init init_workqueues(void)
 	unsigned int cpu;
 	int i;
 
-	cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
+	cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
+	cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
 
 	/* initialize gcwqs */
 	for_each_gcwq_cpu(cpu) {
 		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct worker_pool *pool;
 
 		spin_lock_init(&gcwq->lock);
-		INIT_LIST_HEAD(&gcwq->worklist);
 		gcwq->cpu = cpu;
 		gcwq->flags |= GCWQ_DISASSOCIATED;
 
-		INIT_LIST_HEAD(&gcwq->idle_list);
 		for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
 			INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
 
-		init_timer_deferrable(&gcwq->idle_timer);
-		gcwq->idle_timer.function = idle_worker_timeout;
-		gcwq->idle_timer.data = (unsigned long)gcwq;
+		for_each_worker_pool(pool, gcwq) {
+			pool->gcwq = gcwq;
+			INIT_LIST_HEAD(&pool->worklist);
+			INIT_LIST_HEAD(&pool->idle_list);
+
+			init_timer_deferrable(&pool->idle_timer);
+			pool->idle_timer.function = idle_worker_timeout;
+			pool->idle_timer.data = (unsigned long)pool;
 
-		setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
-			    (unsigned long)gcwq);
+			setup_timer(&pool->mayday_timer, gcwq_mayday_timeout,
+				    (unsigned long)pool);
 
-		ida_init(&gcwq->worker_ida);
+			mutex_init(&pool->manager_mutex);
+			ida_init(&pool->worker_ida);
+		}
 
-		gcwq->trustee_state = TRUSTEE_DONE;
-		init_waitqueue_head(&gcwq->trustee_wait);
+		init_waitqueue_head(&gcwq->rebind_hold);
 	}
 
 	/* create the initial worker */
 	for_each_online_gcwq_cpu(cpu) {
 		struct global_cwq *gcwq = get_gcwq(cpu);
-		struct worker *worker;
+		struct worker_pool *pool;
 
 		if (cpu != WORK_CPU_UNBOUND)
 			gcwq->flags &= ~GCWQ_DISASSOCIATED;
-		worker = create_worker(gcwq, true);
-		BUG_ON(!worker);
-		spin_lock_irq(&gcwq->lock);
-		start_worker(worker);
-		spin_unlock_irq(&gcwq->lock);
+
+		for_each_worker_pool(pool, gcwq) {
+			struct worker *worker;
+
+			worker = create_worker(pool);
+			BUG_ON(!worker);
+			spin_lock_irq(&gcwq->lock);
+			start_worker(worker);
+			spin_unlock_irq(&gcwq->lock);
+		}
 	}
 
 	system_wq = alloc_workqueue("events", 0, 0);