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_T