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

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (55 commits)
  workqueue: mark init_workqueues() as early_initcall()
  workqueue: explain for_each_*cwq_cpu() iterators
  fscache: fix build on !CONFIG_SYSCTL
  slow-work: kill it
  gfs2: use workqueue instead of slow-work
  drm: use workqueue instead of slow-work
  cifs: use workqueue instead of slow-work
  fscache: drop references to slow-work
  fscache: convert operation to use workqueue instead of slow-work
  fscache: convert object to use workqueue instead of slow-work
  workqueue: fix how cpu number is stored in work->data
  workqueue: fix mayday_mask handling on UP
  workqueue: fix build problem on !CONFIG_SMP
  workqueue: fix locking in retry path of maybe_create_worker()
  async: use workqueue for worker pool
  workqueue: remove WQ_SINGLE_CPU and use WQ_UNBOUND instead
  workqueue: implement unbound workqueue
  workqueue: prepare for WQ_UNBOUND implementation
  libata: take advantage of cmwq and remove concurrency limitations
  workqueue: fix worker management invocation without pending works
  ...

Fixed up conflicts in fs/cifs/* as per Tejun. Other trivial conflicts in
include/linux/workqueue.h, kernel/trace/Kconfig and kernel/workqueue.c

1 files changed, 2755 insertions, 405 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 59fef1531dd2..9ca34cddaf6d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -33,41 +33,272 @@
 #include <linux/kallsyms.h>
 #include <linux/debug_locks.h>
 #include <linux/lockdep.h>
-#define CREATE_TRACE_POINTS
-#include <trace/events/workqueue.h>
+#include <linux/idr.h>
+
+#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 */
+
+	/* 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,
+
+	/* 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 */
+
+	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
+	BUSY_WORKER_HASH_SIZE	= 1 << BUSY_WORKER_HASH_ORDER,
+	BUSY_WORKER_HASH_MASK	= BUSY_WORKER_HASH_SIZE - 1,
+
+	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
+	IDLE_WORKER_TIMEOUT	= 300 * HZ,	/* keep idle ones for 5 mins */
+
+	MAYDAY_INITIAL_TIMEOUT	= HZ / 100,	/* call for help after 10ms */
+	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,
+};
 
 /*
- * The per-CPU workqueue (if single thread, we always use the first
- * possible cpu).
+ * Structure fields follow one of the following exclusion rules.
+ *
+ * I: Set during initialization and read-only afterwards.
+ *
+ * P: Preemption protected.  Disabling preemption is enough and should
+ *    only be modified and accessed from the local cpu.
+ *
+ * L: gcwq->lock protected.  Access with gcwq->lock held.
+ *
+ * X: During normal operation, modification requires gcwq->lock and
+ *    should be done only from local cpu.  Either disabling preemption
+ *    on local cpu or grabbing gcwq->lock is enough for read access.
+ *    If GCWQ_DISASSOCIATED is set, it's identical to L.
+ *
+ * F: wq->flush_mutex protected.
+ *
+ * W: workqueue_lock protected.
  */
-struct cpu_workqueue_struct {
 
-	spinlock_t lock;
+struct global_cwq;
 
-	struct list_head worklist;
-	wait_queue_head_t more_work;
-	struct work_struct *current_work;
+/*
+ * The poor guys doing the actual heavy lifting.  All on-duty workers
+ * are either serving the manager role, on idle list or on busy hash.
+ */
+struct worker {
+	/* on idle list while idle, on busy hash table while busy */
+	union {
+		struct list_head	entry;	/* L: while idle */
+		struct hlist_node	hentry;	/* L: while busy */
+	};
 
-	struct workqueue_struct *wq;
-	struct task_struct *thread;
-} ____cacheline_aligned;
+	struct work_struct	*current_work;	/* L: work being processed */
+	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 */
+	/* 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 */
+};
+
+/*
+ * Global per-cpu workqueue.  There's one and only one for each cpu
+ * and all works are queued and processed here regardless of their
+ * target workqueues.
+ */
+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 */
+	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 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 */
+} ____cacheline_aligned_in_smp;
+
+/*
+ * The per-CPU workqueue.  The lower WORK_STRUCT_FLAG_BITS of
+ * work_struct->data are used for flags and thus cwqs need to be
+ * aligned at two's power of the number of flag bits.
+ */
+struct cpu_workqueue_struct {
+	struct global_cwq	*gcwq;		/* I: the associated gcwq */
+	struct workqueue_struct *wq;		/* I: the owning workqueue */
+	int			work_color;	/* L: current color */
+	int			flush_color;	/* L: flushing color */
+	int			nr_in_flight[WORK_NR_COLORS];
+						/* L: nr of in_flight works */
+	int			nr_active;	/* L: nr of active works */
+	int			max_active;	/* L: max active works */
+	struct list_head	delayed_works;	/* L: delayed works */
+};
+
+/*
+ * Structure used to wait for workqueue flush.
+ */
+struct wq_flusher {
+	struct list_head	list;		/* F: list of flushers */
+	int			flush_color;	/* F: flush color waiting for */
+	struct completion	done;		/* flush completion */
+};
+
+/*
+ * All cpumasks are assumed to be always set on UP and thus can't be
+ * used to determine whether there's something to be done.
+ */
+#ifdef CONFIG_SMP
+typedef cpumask_var_t mayday_mask_t;
+#define mayday_test_and_set_cpu(cpu, mask)	\
+	cpumask_test_and_set_cpu((cpu), (mask))
+#define mayday_clear_cpu(cpu, mask)		cpumask_clear_cpu((cpu), (mask))
+#define for_each_mayday_cpu(cpu, mask)		for_each_cpu((cpu), (mask))
+#define alloc_mayday_mask(maskp, gfp)		alloc_cpumask_var((maskp), (gfp))
+#define free_mayday_mask(mask)			free_cpumask_var((mask))
+#else
+typedef unsigned long mayday_mask_t;
+#define mayday_test_and_set_cpu(cpu, mask)	test_and_set_bit(0, &(mask))
+#define mayday_clear_cpu(cpu, mask)		clear_bit(0, &(mask))
+#define for_each_mayday_cpu(cpu, mask)		if ((cpu) = 0, (mask))
+#define alloc_mayday_mask(maskp, gfp)		true
+#define free_mayday_mask(mask)			do { } while (0)
+#endif
 
 /*
  * The externally visible workqueue abstraction is an array of
  * per-CPU workqueues:
  */
 struct workqueue_struct {
-	struct cpu_workqueue_struct *cpu_wq;
-	struct list_head list;
-	const char *name;
-	int singlethread;
-	int freezeable;		/* Freeze threads during suspend */
-	int rt;
+	unsigned int		flags;		/* I: WQ_* flags */
+	union {
+		struct cpu_workqueue_struct __percpu	*pcpu;
+		struct cpu_workqueue_struct		*single;
+		unsigned long				v;
+	} cpu_wq;				/* I: cwq's */
+	struct list_head	list;		/* W: list of all workqueues */
+
+	struct mutex		flush_mutex;	/* protects wq flushing */
+	int			work_color;	/* F: current work color */
+	int			flush_color;	/* F: current flush color */
+	atomic_t		nr_cwqs_to_flush; /* flush in progress */
+	struct wq_flusher	*first_flusher;	/* F: first flusher */
+	struct list_head	flusher_queue;	/* F: flush waiters */
+	struct list_head	flusher_overflow; /* F: flush overflow list */
+
+	mayday_mask_t		mayday_mask;	/* cpus requesting rescue */
+	struct worker		*rescuer;	/* I: rescue worker */
+
+	int			saved_max_active; /* W: saved cwq max_active */
+	const char		*name;		/* I: workqueue name */
 #ifdef CONFIG_LOCKDEP
-	struct lockdep_map lockdep_map;
+	struct lockdep_map	lockdep_map;
 #endif
 };
 
+struct workqueue_struct *system_wq __read_mostly;
+struct workqueue_struct *system_long_wq __read_mostly;
+struct workqueue_struct *system_nrt_wq __read_mostly;
+struct workqueue_struct *system_unbound_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_wq);
+EXPORT_SYMBOL_GPL(system_long_wq);
+EXPORT_SYMBOL_GPL(system_nrt_wq);
+EXPORT_SYMBOL_GPL(system_unbound_wq);
+
+#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)
+
+static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
+				  unsigned int sw)
+{
+	if (cpu < nr_cpu_ids) {
+		if (sw & 1) {
+			cpu = cpumask_next(cpu, mask);
+			if (cpu < nr_cpu_ids)
+				return cpu;
+		}
+		if (sw & 2)
+			return WORK_CPU_UNBOUND;
+	}
+	return WORK_CPU_NONE;
+}
+
+static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
+				struct workqueue_struct *wq)
+{
+	return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
+}
+
+/*
+ * CPU iterators
+ *
+ * An extra gcwq is defined for an invalid cpu number
+ * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
+ * specific CPU.  The following iterators are similar to
+ * for_each_*_cpu() iterators but also considers the unbound gcwq.
+ *
+ * for_each_gcwq_cpu()		: possible CPUs + WORK_CPU_UNBOUND
+ * for_each_online_gcwq_cpu()	: online CPUs + WORK_CPU_UNBOUND
+ * for_each_cwq_cpu()		: possible CPUs for bound workqueues,
+ *				  WORK_CPU_UNBOUND for unbound workqueues
+ */
+#define for_each_gcwq_cpu(cpu)						\
+	for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3);		\
+	     (cpu) < WORK_CPU_NONE;					\
+	     (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
+
+#define for_each_online_gcwq_cpu(cpu)					\
+	for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3);		\
+	     (cpu) < WORK_CPU_NONE;					\
+	     (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
+
+#define for_each_cwq_cpu(cpu, wq)					\
+	for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq));	\
+	     (cpu) < WORK_CPU_NONE;					\
+	     (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
+
 #ifdef CONFIG_LOCKDEP
 /**
  * in_workqueue_context() - in context of specified workqueue?
@@ -122,7 +353,7 @@ static int work_fixup_activate(void *addr, enum debug_obj_state state)
 		 * statically initialized. We just make sure that it
 		 * is tracked in the object tracker.
 		 */
-		if (test_bit(WORK_STRUCT_STATIC, work_data_bits(work))) {
+		if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
 			debug_object_init(work, &work_debug_descr);
 			debug_object_activate(work, &work_debug_descr);
 			return 0;
@@ -196,94 +427,575 @@ static inline void debug_work_deactivate(struct work_struct *work) { }
 /* Serializes the accesses to the list of workqueues. */
 static DEFINE_SPINLOCK(workqueue_lock);
 static LIST_HEAD(workqueues);
+static bool workqueue_freezing;		/* W: have wqs started freezing? */
+
+/*
+ * The almighty global cpu workqueues.  nr_running is the only field
+ * which is expected to be used frequently by other cpus via
+ * 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);
+
+/*
+ * Global cpu workqueue and nr_running counter for unbound gcwq.  The
+ * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
+ * 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 int worker_thread(void *__worker);
+
+static struct global_cwq *get_gcwq(unsigned int cpu)
+{
+	if (cpu != WORK_CPU_UNBOUND)
+		return &per_cpu(global_cwq, cpu);
+	else
+		return &unbound_global_cwq;
+}
+
+static atomic_t *get_gcwq_nr_running(unsigned int cpu)
+{
+	if (cpu != WORK_CPU_UNBOUND)
+		return &per_cpu(gcwq_nr_running, cpu);
+	else
+		return &unbound_gcwq_nr_running;
+}
+
+static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
+					    struct workqueue_struct *wq)
+{
+	if (!(wq->flags & WQ_UNBOUND)) {
+		if (likely(cpu < nr_cpu_ids)) {
+#ifdef CONFIG_SMP
+			return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
+#else
+			return wq->cpu_wq.single;
+#endif
+		}
+	} else if (likely(cpu == WORK_CPU_UNBOUND))
+		return wq->cpu_wq.single;
+	return NULL;
+}
+
+static unsigned int work_color_to_flags(int color)
+{
+	return color << WORK_STRUCT_COLOR_SHIFT;
+}
+
+static int get_work_color(struct work_struct *work)
+{
+	return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
+		((1 << WORK_STRUCT_COLOR_BITS) - 1);
+}
+
+static int work_next_color(int color)
+{
+	return (color + 1) % WORK_NR_COLORS;
+}
 
-static int singlethread_cpu __read_mostly;
-static const struct cpumask *cpu_singlethread_map __read_mostly;
 /*
- * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
- * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
- * which comes in between can't use for_each_online_cpu(). We could
- * use cpu_possible_map, the cpumask below is more a documentation
- * than optimization.
+ * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
+ * work is on queue.  Once execution starts, WORK_STRUCT_CWQ is
+ * cleared and the work data contains the cpu number it was last on.
+ *
+ * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
+ * cwq, cpu or clear work->data.  These functions should only be
+ * called while the work is owned - ie. while the PENDING bit is set.
+ *
+ * get_work_[g]cwq() can be used to obtain the gcwq or cwq
+ * corresponding to a work.  gcwq is available once the work has been
+ * queued anywhere after initialization.  cwq is available only from
+ * queueing until execution starts.
  */
-static cpumask_var_t cpu_populated_map __read_mostly;
+static inline void set_work_data(struct work_struct *work, unsigned long data,
+				 unsigned long flags)
+{
+	BUG_ON(!work_pending(work));
+	atomic_long_set(&work->data, data | flags | work_static(work));
+}
 
-/* If it's single threaded, it isn't in the list of workqueues. */
-static inline int is_wq_single_threaded(struct workqueue_struct *wq)
+static void set_work_cwq(struct work_struct *work,
+			 struct cpu_workqueue_struct *cwq,
+			 unsigned long extra_flags)
 {
-	return wq->singlethread;
+	set_work_data(work, (unsigned long)cwq,
+		      WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
 }
 
-static const struct cpumask *wq_cpu_map(struct workqueue_struct *wq)
+static void set_work_cpu(struct work_struct *work, unsigned int cpu)
 {
-	return is_wq_single_threaded(wq)
-		? cpu_singlethread_map : cpu_populated_map;
+	set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
 }
 
-static
-struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
+static void clear_work_data(struct work_struct *work)
 {
-	if (unlikely(is_wq_single_threaded(wq)))
-		cpu = singlethread_cpu;
-	return per_cpu_ptr(wq->cpu_wq, cpu);
+	set_work_data(work, WORK_STRUCT_NO_CPU, 0);
+}
+
+static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
+{
+	unsigned long data = atomic_long_read(&work->data);
+
+	if (data & WORK_STRUCT_CWQ)
+		return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
+	else
+		return NULL;
+}
+
+static struct global_cwq *get_work_gcwq(struct work_struct *work)
+{
+	unsigned long data = atomic_long_read(&work->data);
+	unsigned int cpu;
+
+	if (data & WORK_STRUCT_CWQ)
+		return ((struct cpu_workqueue_struct *)
+			(data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
+
+	cpu = data >> WORK_STRUCT_FLAG_BITS;
+	if (cpu == WORK_CPU_NONE)
+		return NULL;
+
+	BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
+	return get_gcwq(cpu);
 }
 
 /*
- * Set the workqueue on which a work item is to be run
- * - Must *only* be called if the pending flag is set
+ * 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.
  */
-static inline void set_wq_data(struct work_struct *work,
-				struct cpu_workqueue_struct *cwq)
+
+static bool __need_more_worker(struct global_cwq *gcwq)
 {
-	unsigned long new;
+	return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
+		gcwq->flags & GCWQ_HIGHPRI_PENDING;
+}
 
-	BUG_ON(!work_pending(work));
+/*
+ * Need to wake up a worker?  Called from anything but currently
+ * running workers.
+ */
+static bool need_more_worker(struct global_cwq *gcwq)
+{
+	return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
+}
+
+/* Can I start working?  Called from busy but !running workers. */
+static bool may_start_working(struct global_cwq *gcwq)
+{
+	return gcwq->nr_idle;
+}
+
+/* Do I need to keep working?  Called from currently running workers. */
+static bool keep_working(struct global_cwq *gcwq)
+{
+	atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
+
+	return !list_empty(&gcwq->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)
+{
+	return need_more_worker(gcwq) && !may_start_working(gcwq);
+}
 
-	new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
-	new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
-	atomic_long_set(&work->data, new);
+/* Do I need to be the manager? */
+static bool need_to_manage_workers(struct global_cwq *gcwq)
+{
+	return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
+}
+
+/* Do we have too many workers and should some go away? */
+static bool too_many_workers(struct global_cwq *gcwq)
+{
+	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;
+
+	return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
 }
 
 /*
- * Clear WORK_STRUCT_PENDING and the workqueue on which it was queued.
+ * Wake up functions.
+ */
+
+/* Return the first worker.  Safe with preemption disabled */
+static struct worker *first_worker(struct global_cwq *gcwq)
+{
+	if (unlikely(list_empty(&gcwq->idle_list)))
+		return NULL;
+
+	return list_first_entry(&gcwq->idle_list, struct worker, entry);
+}
+
+/**
+ * wake_up_worker - wake up an idle worker
+ * @gcwq: gcwq to wake worker for
+ *
+ * Wake up the first idle worker of @gcwq.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ */
+static void wake_up_worker(struct global_cwq *gcwq)
+{
+	struct worker *worker = first_worker(gcwq);
+
+	if (likely(worker))
+		wake_up_process(worker->task);
+}
+
+/**
+ * wq_worker_waking_up - a worker is waking up
+ * @task: task waking up
+ * @cpu: CPU @task is waking up to
+ *
+ * This function is called during try_to_wake_up() when a worker is
+ * being awoken.
+ *
+ * CONTEXT:
+ * spin_lock_irq(rq->lock)
+ */
+void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
+{
+	struct worker *worker = kthread_data(task);
+
+	if (likely(!(worker->flags & WORKER_NOT_RUNNING)))
+		atomic_inc(get_gcwq_nr_running(cpu));
+}
+
+/**
+ * wq_worker_sleeping - a worker is going to sleep
+ * @task: task going to sleep
+ * @cpu: CPU in question, must be the current CPU number
+ *
+ * This function is called during schedule() when a busy worker is
+ * going to sleep.  Worker on the same cpu can be woken up by
+ * returning pointer to its task.
+ *
+ * CONTEXT:
+ * spin_lock_irq(rq->lock)
+ *
+ * RETURNS:
+ * Worker task on @cpu to wake up, %NULL if none.
+ */
+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);
+
+	if (unlikely(worker->flags & WORKER_NOT_RUNNING))
+		return NULL;
+
+	/* this can only happen on the local cpu */
+	BUG_ON(cpu != raw_smp_processor_id());
+
+	/*
+	 * The counterpart of the following dec_and_test, implied mb,
+	 * 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.
+	 */
+	if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
+		to_wakeup = first_worker(gcwq);
+	return to_wakeup ? to_wakeup->task : NULL;
+}
+
+/**
+ * worker_set_flags - set worker flags and adjust nr_running accordingly
+ * @worker: self
+ * @flags: flags to set
+ * @wakeup: wakeup an idle worker if necessary
+ *
+ * Set @flags in @worker->flags and adjust nr_running accordingly.  If
+ * nr_running becomes zero and @wakeup is %true, an idle worker is
+ * woken up.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock)
+ */
+static inline void worker_set_flags(struct worker *worker, unsigned int flags,
+				    bool wakeup)
+{
+	struct global_cwq *gcwq = worker->gcwq;
+
+	WARN_ON_ONCE(worker->task != current);
+
+	/*
+	 * If transitioning into NOT_RUNNING, adjust nr_running and
+	 * wake up an idle worker as necessary if requested by
+	 * @wakeup.
+	 */
+	if ((flags & WORKER_NOT_RUNNING) &&
+	    !(worker->flags & WORKER_NOT_RUNNING)) {
+		atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
+
+		if (wakeup) {
+			if (atomic_dec_and_test(nr_running) &&
+			    !list_empty(&gcwq->worklist))
+				wake_up_worker(gcwq);
+		} else
+			atomic_dec(nr_running);
+	}
+
+	worker->flags |= flags;
+}
+
+/**
+ * worker_clr_flags - clear worker flags and adjust nr_running accordingly
+ * @worker: self
+ * @flags: flags to clear
+ *
+ * Clear @flags in @worker->flags and adjust nr_running accordingly.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock)
+ */
+static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
+{
+	struct global_cwq *gcwq = worker->gcwq;
+	unsigned int oflags = worker->flags;
+
+	WARN_ON_ONCE(worker->task != current);
+
+	worker->flags &= ~flags;
+
+	/* if transitioning out of NOT_RUNNING, increment nr_running */
+	if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
+		if (!(worker->flags & WORKER_NOT_RUNNING))
+			atomic_inc(get_gcwq_nr_running(gcwq->cpu));
+}
+
+/**
+ * busy_worker_head - return the busy hash head for a work
+ * @gcwq: gcwq of interest
+ * @work: work to be hashed
+ *
+ * Return hash head of @gcwq for @work.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ *
+ * RETURNS:
+ * Pointer to the hash head.
+ */
+static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
+					   struct work_struct *work)
+{
+	const int base_shift = ilog2(sizeof(struct work_struct));
+	unsigned long v = (unsigned long)work;
+
+	/* simple shift and fold hash, do we need something better? */
+	v >>= base_shift;
+	v += v >> BUSY_WORKER_HASH_ORDER;
+	v &= BUSY_WORKER_HASH_MASK;
+
+	return &gcwq->busy_hash[v];
+}
+
+/**
+ * __find_worker_executing_work - find worker which is executing a work
+ * @gcwq: gcwq of interest
+ * @bwh: hash head as returned by busy_worker_head()
+ * @work: work to find worker for
+ *
+ * Find a worker which is executing @work on @gcwq.  @bwh should be
+ * the hash head obtained by calling busy_worker_head() with the same
+ * work.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ *
+ * RETURNS:
+ * Pointer to worker which is executing @work if found, NULL
+ * otherwise.
+ */
+static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
+						   struct hlist_head *bwh,
+						   struct work_struct *work)
+{
+	struct worker *worker;
+	struct hlist_node *tmp;
+
+	hlist_for_each_entry(worker, tmp, bwh, hentry)
+		if (worker->current_work == work)
+			return worker;
+	return NULL;
+}
+
+/**
+ * find_worker_executing_work - find worker which is executing a work
+ * @gcwq: gcwq of interest
+ * @work: work to find worker for
+ *
+ * Find a worker which is executing @work on @gcwq.  This function is
+ * identical to __find_worker_executing_work() except that this
+ * function calculates @bwh itself.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ *
+ * RETURNS:
+ * Pointer to worker which is executing @work if found, NULL
+ * otherwise.
  */
-static inline void clear_wq_data(struct work_struct *work)
+static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
+						 struct work_struct *work)
 {
-	unsigned long flags = *work_data_bits(work) &
-				(1UL << WORK_STRUCT_STATIC);
-	atomic_long_set(&work->data, flags);
+	return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
+					    work);
 }
 
-static inline
-struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
+/**
+ * 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)
 {
-	return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
+	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
+ * @head: insertion point
+ * @extra_flags: extra WORK_STRUCT_* flags to set
+ *
+ * Insert @work which belongs to @cwq into @gcwq after @head.
+ * @extra_flags is or'd to work_struct flags.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ */
 static void insert_work(struct cpu_workqueue_struct *cwq,
-			struct work_struct *work, struct list_head *head)
+			struct work_struct *work, struct list_head *head,
+			unsigned int extra_flags)
 {
-	trace_workqueue_insertion(cwq->thread, work);
+	struct global_cwq *gcwq = cwq->gcwq;
+
+	/* we own @work, set data and link */
+	set_work_cwq(work, cwq, extra_flags);
 
-	set_wq_data(work, cwq);
 	/*
 	 * Ensure that we get the right work->data if we see the
 	 * result of list_add() below, see try_to_grab_pending().
 	 */
 	smp_wmb();
+
 	list_add_tail(&work->entry, head);
-	wake_up(&cwq->more_work);
+
+	/*
+	 * Ensure either worker_sched_deactivated() sees the above
+	 * list_add_tail() or we see zero nr_running to avoid workers
+	 * lying around lazily while there are works to be processed.
+	 */
+	smp_mb();
+
+	if (__need_more_worker(gcwq))
+		wake_up_worker(gcwq);
 }
 
-static void __queue_work(struct cpu_workqueue_struct *cwq,
+static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 			 struct work_struct *work)
 {
+	struct global_cwq *gcwq;
+	struct cpu_workqueue_struct *cwq;
+	struct list_head *worklist;
 	unsigned long flags;
 
 	debug_work_activate(work);
-	spin_lock_irqsave(&cwq->lock, flags);
-	insert_work(cwq, work, &cwq->worklist);
-	spin_unlock_irqrestore(&cwq->lock, flags);
+
+	/* determine gcwq to use */
+	if (!(wq->flags & WQ_UNBOUND)) {
+		struct global_cwq *last_gcwq;
+
+		if (unlikely(cpu == WORK_CPU_UNBOUND))
+			cpu = raw_smp_processor_id();
+
+		/*
+		 * It's multi cpu.  If @wq is non-reentrant and @work
+		 * was previously on a different cpu, it might still
+		 * be running there, in which case the work needs to
+		 * be queued on that cpu to guarantee non-reentrance.
+		 */
+		gcwq = get_gcwq(cpu);
+		if (wq->flags & WQ_NON_REENTRANT &&
+		    (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
+			struct worker *worker;
+
+			spin_lock_irqsave(&last_gcwq->lock, flags);
+
+			worker = find_worker_executing_work(last_gcwq, work);
+
+			if (worker && worker->current_cwq->wq == wq)
+				gcwq = last_gcwq;
+			else {
+				/* meh... not running there, queue here */
+				spin_unlock_irqrestore(&last_gcwq->lock, flags);
+				spin_lock_irqsave(&gcwq->lock, flags);
+			}
+		} else
+			spin_lock_irqsave(&gcwq->lock, flags);
+	} else {
+		gcwq = get_gcwq(WORK_CPU_UNBOUND);
+		spin_lock_irqsave(&gcwq->lock, flags);
+	}
+
+	/* gcwq determined, get cwq and queue */
+	cwq = get_cwq(gcwq->cpu, wq);
+
+	BUG_ON(!list_empty(&work->entry));
+
+	cwq->nr_in_flight[cwq->work_color]++;
+
+	if (likely(cwq->nr_active < cwq->max_active)) {
+		cwq->nr_active++;
+		worklist = gcwq_determine_ins_pos(gcwq, cwq);
+	} else
+		worklist = &cwq->delayed_works;
+
+	insert_work(cwq, work, worklist, work_color_to_flags(cwq->work_color));
+
+	spin_unlock_irqrestore(&gcwq->lock, flags);
 }
 
 /**
@@ -323,9 +1035,8 @@ queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
 {
 	int ret = 0;
 
-	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
-		BUG_ON(!list_empty(&work->entry));
-		__queue_work(wq_per_cpu(wq, cpu), work);
+	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
+		__queue_work(cpu, wq, work);
 		ret = 1;
 	}
 	return ret;
@@ -335,10 +1046,9 @@ EXPORT_SYMBOL_GPL(queue_work_on);
 static void delayed_work_timer_fn(unsigned long __data)
 {
 	struct delayed_work *dwork = (struct delayed_work *)__data;
-	struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
-	struct workqueue_struct *wq = cwq->wq;
+	struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
 
-	__queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
+	__queue_work(smp_processor_id(), cwq->wq, &dwork->work);
 }
 
 /**
@@ -375,14 +1085,31 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 	struct timer_list *timer = &dwork->timer;
 	struct work_struct *work = &dwork->work;
 
-	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
+	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
+		unsigned int lcpu;
+
 		BUG_ON(timer_pending(timer));
 		BUG_ON(!list_empty(&work->entry));
 
 		timer_stats_timer_set_start_info(&dwork->timer);
 
-		/* This stores cwq for the moment, for the timer_fn */
-		set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
+		/*
+		 * This stores cwq for the moment, for the timer_fn.
+		 * Note that the work's gcwq is preserved to allow
+		 * reentrance detection for delayed works.
+		 */
+		if (!(wq->flags & WQ_UNBOUND)) {
+			struct global_cwq *gcwq = get_work_gcwq(work);
+
+			if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
+				lcpu = gcwq->cpu;
+			else
+				lcpu = raw_smp_processor_id();
+		} else
+			lcpu = WORK_CPU_UNBOUND;
+
+		set_work_cwq(work, get_cwq(lcpu, wq), 0);
+
 		timer->expires = jiffies + delay;
 		timer->data = (unsigned long)dwork;
 		timer->function = delayed_work_timer_fn;
@@ -397,80 +1124,872 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 }
 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 
-static void run_workqueue(struct cpu_workqueue_struct *cwq)
+/**
+ * worker_enter_idle - enter idle state
+ * @worker: worker which is entering idle state
+ *
+ * @worker is entering idle state.  Update stats and idle timer if
+ * necessary.
+ *
+ * LOCKING:
+ * spin_lock_irq(gcwq->lock).
+ */
+static void worker_enter_idle(struct worker *worker)
 {
-	spin_lock_irq(&cwq->lock);
-	while (!list_empty(&cwq->worklist)) {
-		struct work_struct *work = list_entry(cwq->worklist.next,
-						struct work_struct, entry);
-		work_func_t f = work->func;
-#ifdef CONFIG_LOCKDEP
+	struct global_cwq *gcwq = worker->gcwq;
+
+	BUG_ON(worker->flags & WORKER_IDLE);
+	BUG_ON(!list_empty(&worker->entry) &&
+	       (worker->hentry.next || worker->hentry.pprev));
+
+	/* can't use worker_set_flags(), also called from start_worker() */
+	worker->flags |= WORKER_IDLE;
+	gcwq->nr_idle++;
+	worker->last_active = jiffies;
+
+	/* idle_list is LIFO */
+	list_add(&worker->entry, &gcwq->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);
+
+	/* sanity check nr_running */
+	WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
+		     atomic_read(get_gcwq_nr_running(gcwq->cpu)));
+}
+
+/**
+ * worker_leave_idle - leave idle state
+ * @worker: worker which is leaving idle state
+ *
+ * @worker is leaving idle state.  Update stats.
+ *
+ * LOCKING:
+ * spin_lock_irq(gcwq->lock).
+ */
+static void worker_leave_idle(struct worker *worker)
+{
+	struct global_cwq *gcwq = worker->gcwq;
+
+	BUG_ON(!(worker->flags & WORKER_IDLE));
+	worker_clr_flags(worker, WORKER_IDLE);
+	gcwq->nr_idle--;
+	list_del_init(&worker->entry);
+}
+
+/**
+ * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
+ * @worker: self
+ *
+ * Works which are scheduled while the cpu is online must at least be
+ * scheduled to a worker which is bound to the cpu so that if they are
+ * flushed from cpu callbacks while cpu is going down, they are
+ * guaranteed to execute on the cpu.
+ *
+ * This function is to be used by rogue workers and rescuers to bind
+ * themselves to the target cpu and may race with cpu going down or
+ * coming online.  kthread_bind() can't be used because it may put the
+ * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
+ * 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.
+ *
+ * CONTEXT:
+ * Might sleep.  Called without any lock but returns with gcwq->lock
+ * held.
+ *
+ * RETURNS:
+ * %true if the associated gcwq is online (@worker is successfully
+ * bound), %false if offline.
+ */
+static bool worker_maybe_bind_and_lock(struct worker *worker)
+{
+	struct global_cwq *gcwq = worker->gcwq;
+	struct task_struct *task = worker->task;
+
+	while (true) {
 		/*
-		 * It is permissible to free the struct work_struct
-		 * from inside the function that is called from it,
-		 * this we need to take into account for lockdep too.
-		 * To avoid bogus "held lock freed" warnings as well
-		 * as problems when looking into work->lockdep_map,
-		 * make a copy and use that here.
+		 * The following call may fail, succeed or succeed
+		 * without actually migrating the task to the cpu if
+		 * it races with cpu hotunplug operation.  Verify
+		 * against GCWQ_DISASSOCIATED.
 		 */
-		struct lockdep_map lockdep_map = work->lockdep_map;
-#endif
-		trace_workqueue_execution(cwq->thread, work);
-		debug_work_deactivate(work);
-		cwq->current_work = work;
-		list_del_init(cwq->worklist.next);
-		spin_unlock_irq(&cwq->lock);
-
-		BUG_ON(get_wq_data(work) != cwq);
-		work_clear_pending(work);
-		lock_map_acquire(&cwq->wq->lockdep_map);
-		lock_map_acquire(&lockdep_map);
-		f(work);
-		lock_map_release(&lockdep_map);
-		lock_map_release(&cwq->wq->lockdep_map);
-
-		if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
-			printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
-					"%s/0x%08x/%d\n",
-					current->comm, preempt_count(),
-				       	task_pid_nr(current));
-			printk(KERN_ERR "    last function: ");
-			print_symbol("%s\n", (unsigned long)f);
-			debug_show_held_locks(current);
-			dump_stack();
+		if (!(gcwq->flags & GCWQ_DISASSOCIATED))
+			set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
+
+		spin_lock_irq(&gcwq->lock);
+		if (gcwq->flags & GCWQ_DISASSOCIATED)
+			return false;
+		if (task_cpu(task) == gcwq->cpu &&
+		    cpumask_equal(&current->cpus_allowed,
+				  get_cpu_mask(gcwq->cpu)))
+			return true;
+		spin_unlock_irq(&gcwq->lock);
+
+		/* CPU has come up inbetween, retry migration */
+		cpu_relax();
+	}
+}
+
+/*
+ * 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.
+ */
+static void worker_rebind_fn(struct work_struct *work)
+{
+	struct worker *worker = container_of(work, struct worker, rebind_work);
+	struct global_cwq *gcwq = worker->gcwq;
+
+	if (worker_maybe_bind_and_lock(worker))
+		worker_clr_flags(worker, WORKER_REBIND);
+
+	spin_unlock_irq(&gcwq->lock);
+}
+
+static struct worker *alloc_worker(void)
+{
+	struct worker *worker;
+
+	worker = kzalloc(sizeof(*worker), GFP_KERNEL);
+	if (worker) {
+		INIT_LIST_HEAD(&worker->entry);
+		INIT_LIST_HEAD(&worker->scheduled);
+		INIT_WORK(&worker->rebind_work, worker_rebind_fn);
+		/* on creation a worker is in !idle && prep state */
+		worker->flags = WORKER_PREP;
+	}
+	return worker;
+}
+
+/**
+ * create_worker - create a new workqueue worker
+ * @gcwq: gcwq the new worker will belong to
+ * @bind: whether to set affinity to @cpu or not
+ *
+ * Create a new worker which is bound to @gcwq.  The returned worker
+ * can be started by calling start_worker() or destroyed using
+ * destroy_worker().
+ *
+ * CONTEXT:
+ * Might sleep.  Does GFP_KERNEL allocations.
+ *
+ * RETURNS:
+ * Pointer to the newly created worker.
+ */
+static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
+{
+	bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
+	struct worker *worker = NULL;
+	int id = -1;
+
+	spin_lock_irq(&gcwq->lock);
+	while (ida_get_new(&gcwq->worker_ida, &id)) {
+		spin_unlock_irq(&gcwq->lock);
+		if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
+			goto fail;
+		spin_lock_irq(&gcwq->lock);
+	}
+	spin_unlock_irq(&gcwq->lock);
+
+	worker = alloc_worker();
+	if (!worker)
+		goto fail;
+
+	worker->gcwq = gcwq;
+	worker->id = id;
+
+	if (!on_unbound_cpu)
+		worker->task = kthread_create(worker_thread, worker,
+					      "kworker/%u:%d", gcwq->cpu, id);
+	else
+		worker->task = kthread_create(worker_thread, worker,
+					      "kworker/u:%d", id);
+	if (IS_ERR(worker->task))
+		goto fail;
+
+	/*
+	 * A rogue worker will become a regular one if CPU comes
+	 * online later on.  Make sure every worker has
+	 * PF_THREAD_BOUND set.
+	 */
+	if (bind && !on_unbound_cpu)
+		kthread_bind(worker->task, gcwq->cpu);
+	else {
+		worker->task->flags |= PF_THREAD_BOUND;
+		if (on_unbound_cpu)
+			worker->flags |= WORKER_UNBOUND;
+	}
+
+	return worker;
+fail:
+	if (id >= 0) {
+		spin_lock_irq(&gcwq->lock);
+		ida_remove(&gcwq->worker_ida, id);
+		spin_unlock_irq(&gcwq->lock);
+	}
+	kfree(worker);
+	return NULL;
+}
+
+/**
+ * start_worker - start a newly created worker
+ * @worker: worker to start
+ *
+ * Make the gcwq aware of @worker and start it.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ */
+static void start_worker(struct worker *worker)
+{
+	worker->flags |= WORKER_STARTED;
+	worker->gcwq->nr_workers++;
+	worker_enter_idle(worker);
+	wake_up_process(worker->task);
+}
+
+/**
+ * destroy_worker - destroy a workqueue worker
+ * @worker: worker to be destroyed
+ *
+ * Destroy @worker and adjust @gcwq stats accordingly.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock) which is released and regrabbed.
+ */
+static void destroy_worker(struct worker *worker)
+{
+	struct global_cwq *gcwq = worker->gcwq;
+	int id = worker->id;
+
+	/* sanity check frenzy */
+	BUG_ON(worker->current_work);
+	BUG_ON(!list_empty(&worker->scheduled));
+
+	if (worker->flags & WORKER_STARTED)
+		gcwq->nr_workers--;
+	if (worker->flags & WORKER_IDLE)
+		gcwq->nr_idle--;
+
+	list_del_init(&worker->entry);
+	worker->flags |= WORKER_DIE;
+
+	spin_unlock_irq(&gcwq->lock);
+
+	kthread_stop(worker->task);
+	kfree(worker);
+
+	spin_lock_irq(&gcwq->lock);
+	ida_remove(&gcwq->worker_ida, id);
+}
+
+static void idle_worker_timeout(unsigned long __gcwq)
+{
+	struct global_cwq *gcwq = (void *)__gcwq;
+
+	spin_lock_irq(&gcwq->lock);
+
+	if (too_many_workers(gcwq)) {
+		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);
+		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
+
+		if (time_before(jiffies, expires))
+			mod_timer(&gcwq->idle_timer, expires);
+		else {
+			/* it's been idle for too long, wake up manager */
+			gcwq->flags |= GCWQ_MANAGE_WORKERS;
+			wake_up_worker(gcwq);
+		}
+	}
+
+	spin_unlock_irq(&gcwq->lock);
+}
+
+static bool send_mayday(struct work_struct *work)
+{
+	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
+	struct workqueue_struct *wq = cwq->wq;
+	unsigned int cpu;
+
+	if (!(wq->flags & WQ_RESCUER))
+		return false;
+
+	/* mayday mayday mayday */
+	cpu = cwq->gcwq->cpu;
+	/* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
+	if (cpu == WORK_CPU_UNBOUND)
+		cpu = 0;
+	if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
+		wake_up_process(wq->rescuer->task);
+	return true;
+}
+
+static void gcwq_mayday_timeout(unsigned long __gcwq)
+{
+	struct global_cwq *gcwq = (void *)__gcwq;
+	struct work_struct *work;
+
+	spin_lock_irq(&gcwq->lock);
+
+	if (need_to_create_worker(gcwq)) {
+		/*
+		 * 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)
+			send_mayday(work);
+	}
+
+	spin_unlock_irq(&gcwq->lock);
+
+	mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
+}
+
+/**
+ * maybe_create_worker - create a new worker if necessary
+ * @gcwq: gcwq to create a new worker for
+ *
+ * Create a new worker for @gcwq if necessary.  @gcwq 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
+ * possible allocation deadlock.
+ *
+ * On return, need_to_create_worker() is guaranteed to be false and
+ * may_start_working() true.
+ *
+ * LOCKING:
+ * spin_lock_irq(gcwq->lock) which may be released and regrabbed
+ * multiple times.  Does GFP_KERNEL allocations.  Called only from
+ * manager.
+ *
+ * RETURNS:
+ * false if no action was taken and gcwq->lock stayed locked, true
+ * otherwise.
+ */
+static bool maybe_create_worker(struct global_cwq *gcwq)
+{
+	if (!need_to_create_worker(gcwq))
+		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);
+
+	while (true) {
+		struct worker *worker;
+
+		worker = create_worker(gcwq, true);
+		if (worker) {
+			del_timer_sync(&gcwq->mayday_timer);
+			spin_lock_irq(&gcwq->lock);
+			start_worker(worker);
+			BUG_ON(need_to_create_worker(gcwq));
+			return true;
+		}
+
+		if (!need_to_create_worker(gcwq))
+			break;
+
+		__set_current_state(TASK_INTERRUPTIBLE);
+		schedule_timeout(CREATE_COOLDOWN);
+
+		if (!need_to_create_worker(gcwq))
+			break;
+	}
+
+	del_timer_sync(&gcwq->mayday_timer);
+	spin_lock_irq(&gcwq->lock);
+	if (need_to_create_worker(gcwq))
+		goto restart;
+	return true;
+}
+
+/**
+ * maybe_destroy_worker - destroy workers which have been idle for a while
+ * @gcwq: gcwq to destroy workers for
+ *
+ * Destroy @gcwq workers which have been idle for longer than
+ * IDLE_WORKER_TIMEOUT.
+ *
+ * LOCKING:
+ * spin_lock_irq(gcwq->lock) which may be released and regrabbed
+ * multiple times.  Called only from manager.
+ *
+ * RETURNS:
+ * false if no action was taken and gcwq->lock stayed locked, true
+ * otherwise.
+ */
+static bool maybe_destroy_workers(struct global_cwq *gcwq)
+{
+	bool ret = false;
+
+	while (too_many_workers(gcwq)) {
+		struct worker *worker;
+		unsigned long expires;
+
+		worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
+		expires = worker->last_active + IDLE_WORKER_TIMEOUT;
+
+		if (time_before(jiffies, expires)) {
+			mod_timer(&gcwq->idle_timer, expires);
+			break;
 		}
 
-		spin_lock_irq(&cwq->lock);
-		cwq->current_work = NULL;
+		destroy_worker(worker);
+		ret = true;
 	}
-	spin_unlock_irq(&cwq->lock);
+
+	return ret;
 }
 
-static int worker_thread(void *__cwq)
+/**
+ * manage_workers - manage worker pool
+ * @worker: self
+ *
+ * Assume the manager role and manage gcwq worker pool @worker belongs
+ * to.  At any given time, there can be only zero or one manager per
+ * gcwq.  The exclusion is handled automatically by this function.
+ *
+ * The caller can safely start processing works on false return.  On
+ * true return, it's guaranteed that need_to_create_worker() is false
+ * and may_start_working() is true.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock) which may be released and regrabbed
+ * multiple times.  Does GFP_KERNEL allocations.
+ *
+ * RETURNS:
+ * false if no action was taken and gcwq->lock stayed locked, true if
+ * some action was taken.
+ */
+static bool manage_workers(struct worker *worker)
 {
-	struct cpu_workqueue_struct *cwq = __cwq;
-	DEFINE_WAIT(wait);
+	struct global_cwq *gcwq = worker->gcwq;
+	bool ret = false;
 
-	if (cwq->wq->freezeable)
-		set_freezable();
+	if (gcwq->flags & GCWQ_MANAGING_WORKERS)
+		return ret;
 
-	for (;;) {
-		prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
-		if (!freezing(current) &&
-		    !kthread_should_stop() &&
-		    list_empty(&cwq->worklist))
-			schedule();
-		finish_wait(&cwq->more_work, &wait);
+	gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
+	gcwq->flags |= GCWQ_MANAGING_WORKERS;
 
-		try_to_freeze();
+	/*
+	 * 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);
+
+	return ret;
+}
+
+/**
+ * move_linked_works - move linked works to a list
+ * @work: start of series of works to be scheduled
+ * @head: target list to append @work to
+ * @nextp: out paramter for nested worklist walking
+ *
+ * Schedule linked works starting from @work to @head.  Work series to
+ * be scheduled starts at @work and includes any consecutive work with
+ * WORK_STRUCT_LINKED set in its predecessor.
+ *
+ * If @nextp is not NULL, it's updated to point to the next work of
+ * the last scheduled work.  This allows move_linked_works() to be
+ * nested inside outer list_for_each_entry_safe().
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ */
+static void move_linked_works(struct work_struct *work, struct list_head *head,
+			      struct work_struct **nextp)
+{
+	struct work_struct *n;
 
-		if (kthread_should_stop())
+	/*
+	 * Linked worklist will always end before the end of the list,
+	 * use NULL for list head.
+	 */
+	list_for_each_entry_safe_from(work, n, NULL, entry) {
+		list_move_tail(&work->entry, head);
+		if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
 			break;
+	}
+
+	/*
+	 * If we're already inside safe list traversal and have moved
+	 * multiple works to the scheduled queue, the next position
+	 * needs to be updated.
+	 */
+	if (nextp)
+		*nextp = n;
+}
 
-		run_workqueue(cwq);
+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);
+
+	move_linked_works(work, pos, NULL);
+	cwq->nr_active++;
+}
+
+/**
+ * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
+ * @cwq: cwq of interest
+ * @color: color of work which left the queue
+ *
+ * A work either has completed or is removed from pending queue,
+ * decrement nr_in_flight of its cwq and handle workqueue flushing.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ */
+static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color)
+{
+	/* ignore uncolored works */
+	if (color == WORK_NO_COLOR)
+		return;
+
+	cwq->nr_in_flight[color]--;
+	cwq->nr_active--;
+
+	if (!list_empty(&cwq->delayed_works)) {
+		/* one down, submit a delayed one */
+		if (cwq->nr_active < cwq->max_active)
+			cwq_activate_first_delayed(cwq);
 	}
 
-	return 0;
+	/* is flush in progress and are we at the flushing tip? */
+	if (likely(cwq->flush_color != color))
+		return;
+
+	/* are there still in-flight works? */
+	if (cwq->nr_in_flight[color])
+		return;
+
+	/* this cwq is done, clear flush_color */
+	cwq->flush_color = -1;
+
+	/*
+	 * If this was the last cwq, wake up the first flusher.  It
+	 * will handle the rest.
+	 */
+	if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
+		complete(&cwq->wq->first_flusher->done);
+}
+
+/**
+ * process_one_work - process single work
+ * @worker: self
+ * @work: work to process
+ *
+ * Process @work.  This function contains all the logics necessary to
+ * process a single work including synchronization against and
+ * interaction with other workers on the same cpu, queueing and
+ * flushing.  As long as context requirement is met, any worker can
+ * call this function to process a work.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock) which is released and regrabbed.
+ */
+static void process_one_work(struct worker *worker, struct work_struct *work)
+{
+	struct cpu_workqueue_struct *cwq = get_work_cwq(work);
+	struct global_cwq *gcwq = cwq->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;
+	int work_color;
+	struct worker *collision;
+#ifdef CONFIG_LOCKDEP
+	/*
+	 * It is permissible to free the struct work_struct from
+	 * inside the function that is called from it, this we need to
+	 * take into account for lockdep too.  To avoid bogus "held
+	 * lock freed" warnings as well as problems when looking into
+	 * work->lockdep_map, make a copy and use that here.
+	 */
+	struct lockdep_map lockdep_map = work->lockdep_map;
+#endif
+	/*
+	 * A single work shouldn't be executed concurrently by
+	 * multiple workers on a single cpu.  Check whether anyone is
+	 * already processing the work.  If so, defer the work to the
+	 * currently executing one.
+	 */
+	collision = __find_worker_executing_work(gcwq, bwh, work);
+	if (unlikely(collision)) {
+		move_linked_works(work, &collision->scheduled, NULL);
+		return;
+	}
+
+	/* claim and process */
+	debug_work_deactivate(work);
+	hlist_add_head(&worker->hentry, bwh);
+	worker->current_work = work;
+	worker->current_cwq = cwq;
+	work_color = get_work_color(work);
+
+	/* record the current cpu number in the work data and dequeue */
+	set_work_cpu(work, gcwq->cpu);
+	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);
+
+	spin_unlock_irq(&gcwq->lock);
+
+	work_clear_pending(work);
+	lock_map_acquire(&cwq->wq->lockdep_map);
+	lock_map_acquire(&lockdep_map);
+	f(work);
+	lock_map_release(&lockdep_map);
+	lock_map_release(&cwq->wq->lockdep_map);
+
+	if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
+		printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
+		       "%s/0x%08x/%d\n",
+		       current->comm, preempt_count(), task_pid_nr(current));
+		printk(KERN_ERR "    last function: ");
+		print_symbol("%s\n", (unsigned long)f);
+		debug_show_held_locks(current);
+		dump_stack();
+	}
+
+	spin_lock_irq(&gcwq->lock);
+
+	/* clear cpu intensive status */
+	if (unlikely(cpu_intensive))
+		worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
+
+	/* we're done with it, release */
+	hlist_del_init(&worker->hentry);
+	worker->current_work = NULL;
+	worker->current_cwq = NULL;
+	cwq_dec_nr_in_flight(cwq, work_color);
+}
+
+/**
+ * process_scheduled_works - process scheduled works
+ * @worker: self
+ *
+ * Process all scheduled works.  Please note that the scheduled list
+ * may change while processing a work, so this function repeatedly
+ * fetches a work from the top and executes it.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock) which may be released and regrabbed
+ * multiple times.
+ */
+static void process_scheduled_works(struct worker *worker)
+{
+	while (!list_empty(&worker->scheduled)) {
+		struct work_struct *work = list_first_entry(&worker->scheduled,
+						struct work_struct, entry);
+		process_one_work(worker, work);
+	}
+}
+
+/**
+ * worker_thread - the worker thread function
+ * @__worker: self
+ *
+ * The gcwq worker thread function.  There's a single dynamic pool of
+ * these per each cpu.  These workers process all works regardless of
+ * their specific target workqueue.  The only exception is works which
+ * belong to workqueues with a rescuer which will be explained in
+ * rescuer_thread().
+ */
+static int worker_thread(void *__worker)
+{
+	struct worker *worker = __worker;
+	struct global_cwq *gcwq = worker->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) {
+		spin_unlock_irq(&gcwq->lock);
+		worker->task->flags &= ~PF_WQ_WORKER;
+		return 0;
+	}
+
+	worker_leave_idle(worker);
+recheck:
+	/* no more worker necessary? */
+	if (!need_more_worker(gcwq))
+		goto sleep;
+
+	/* do we need to manage? */
+	if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
+		goto recheck;
+
+	/*
+	 * ->scheduled list can only be filled while a worker is
+	 * preparing to process a work or actually processing it.
+	 * Make sure nobody diddled with it while I was sleeping.
+	 */
+	BUG_ON(!list_empty(&worker->scheduled));
+
+	/*
+	 * When control reaches this point, we're guaranteed to have
+	 * at least one idle worker or that someone else has already
+	 * assumed the manager role.
+	 */
+	worker_clr_flags(worker, WORKER_PREP);
+
+	do {
+		struct work_struct *work =
+			list_first_entry(&gcwq->worklist,
+					 struct work_struct, entry);
+
+		if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
+			/* optimization path, not strictly necessary */
+			process_one_work(worker, work);
+			if (unlikely(!list_empty(&worker->scheduled)))
+				process_scheduled_works(worker);
+		} else {
+			move_linked_works(work, &worker->scheduled, NULL);
+			process_scheduled_works(worker);
+		}
+	} while (keep_working(gcwq));
+
+	worker_set_flags(worker, WORKER_PREP, false);
+sleep:
+	if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
+		goto recheck;
+
+	/*
+	 * gcwq->lock is held and there's no work to process and no
+	 * need to manage, sleep.  Workers are woken up only while
+	 * holding gcwq->lock or from local cpu, so setting the
+	 * current state before releasing gcwq->lock is enough to
+	 * prevent losing any event.
+	 */
+	worker_enter_idle(worker);
+	__set_current_state(TASK_INTERRUPTIBLE);
+	spin_unlock_irq(&gcwq->lock);
+	schedule();
+	goto woke_up;
+}
+
+/**
+ * rescuer_thread - the rescuer thread function
+ * @__wq: the associated workqueue
+ *
+ * Workqueue rescuer thread function.  There's one rescuer for each
+ * workqueue which has WQ_RESCUER set.
+ *
+ * Regular work processing on a gcwq may block trying to create a new
+ * worker which uses GFP_KERNEL allocation which has slight chance of
+ * developing into deadlock if some works currently on the same queue
+ * need to be processed to satisfy the GFP_KERNEL allocation.  This is
+ * the problem rescuer solves.
+ *
+ * When such condition is possible, the gcwq summons rescuers of all
+ * workqueues which have works queued on the gcwq and let them process
+ * those works so that forward progress can be guaranteed.
+ *
+ * This should happen rarely.
+ */
+static int rescuer_thread(void *__wq)
+{
+	struct workqueue_struct *wq = __wq;
+	struct worker *rescuer = wq->rescuer;
+	struct list_head *scheduled = &rescuer->scheduled;
+	bool is_unbound = wq->flags & WQ_UNBOUND;
+	unsigned int cpu;
+
+	set_user_nice(current, RESCUER_NICE_LEVEL);
+repeat:
+	set_current_state(TASK_INTERRUPTIBLE);
+
+	if (kthread_should_stop())
+		return 0;
+
+	/*
+	 * See whether any cpu is asking for help.  Unbounded
+	 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
+	 */
+	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 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;
+		worker_maybe_bind_and_lock(rescuer);
+
+		/*
+		 * Slurp in all works issued via this workqueue and
+		 * process'em.
+		 */
+		BUG_ON(!list_empty(&rescuer->scheduled));
+		list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
+			if (get_work_cwq(work) == cwq)
+				move_linked_works(work, scheduled, &n);
+
+		process_scheduled_works(rescuer);
+		spin_unlock_irq(&gcwq->lock);
+	}
+
+	schedule();
+	goto repeat;
 }
 
 struct wq_barrier {
@@ -484,44 +2003,137 @@ static void wq_barrier_func(struct work_struct *work)
 	complete(&barr->done);
 }
 
+/**
+ * insert_wq_barrier - insert a barrier work
+ * @cwq: cwq to insert barrier into
+ * @barr: wq_barrier to insert
+ * @target: target work to attach @barr to
+ * @worker: worker currently executing @target, NULL if @target is not executing
+ *
+ * @barr is linked to @target such that @barr is completed only after
+ * @target finishes execution.  Please note that the ordering
+ * guarantee is observed only with respect to @target and on the local
+ * cpu.
+ *
+ * Currently, a queued barrier can't be canceled.  This is because
+ * try_to_grab_pending() can't determine whether the work to be
+ * grabbed is at the head of the queue and thus can't clear LINKED
+ * flag of the previous work while there must be a valid next work
+ * after a work with LINKED flag set.
+ *
+ * Note that when @worker is non-NULL, @target may be modified
+ * underneath us, so we can't reliably determine cwq from @target.
+ *
+ * CONTEXT:
+ * spin_lock_irq(gcwq->lock).
+ */
 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
-			struct wq_barrier *barr, struct list_head *head)
+			      struct wq_barrier *barr,
+			      struct work_struct *target, struct worker *worker)
 {
+	struct list_head *head;
+	unsigned int linked = 0;
+
 	/*
-	 * debugobject calls are safe here even with cwq->lock locked
+	 * debugobject calls are safe here even with gcwq->lock locked
 	 * as we know for sure that this will not trigger any of the
 	 * checks and call back into the fixup functions where we
 	 * might deadlock.
 	 */
 	INIT_WORK_ON_STACK(&barr->work, wq_barrier_func);
-	__set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
-
+	__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
 	init_completion(&barr->done);
 
+	/*
+	 * If @target is currently being executed, schedule the
+	 * barrier to the worker; otherwise, put it after @target.
+	 */
+	if (worker)
+		head = worker->scheduled.next;
+	else {
+		unsigned long *bits = work_data_bits(target);
+
+		head = target->entry.next;
+		/* there can already be other linked works, inherit and set */
+		linked = *bits & WORK_STRUCT_LINKED;
+		__set_bit(WORK_STRUCT_LINKED_BIT, bits);
+	}
+
 	debug_work_activate(&barr->work);
-	insert_work(cwq, &barr->work, head);
+	insert_work(cwq, &barr->work, head,
+		    work_color_to_flags(WORK_NO_COLOR) | linked);
 }
 
-static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
+/**
+ * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
+ * @wq: workqueue being flushed
+ * @flush_color: new flush color, < 0 for no-op
+ * @work_color: new work color, < 0 for no-op
+ *
+ * Prepare cwqs for workqueue flushing.
+ *
+ * If @flush_color is non-negative, flush_color on all cwqs should be
+ * -1.  If no cwq has in-flight commands at the specified color, all
+ * cwq->flush_color's stay at -1 and %false is returned.  If any cwq
+ * has in flight commands, its cwq->flush_color is set to
+ * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
+ * wakeup logic is armed and %true is returned.
+ *
+ * The caller should have initialized @wq->first_flusher prior to
+ * calling this function with non-negative @flush_color.  If
+ * @flush_color is negative, no flush color update is done and %false
+ * is returned.
+ *
+ * If @work_color is non-negative, all cwqs should have the same
+ * work_color which is previous to @work_color and all will be
+ * advanced to @work_color.
+ *
+ * CONTEXT:
+ * mutex_lock(wq->flush_mutex).
+ *
+ * RETURNS:
+ * %true if @flush_color >= 0 and there's something to flush.  %false
+ * otherwise.
+ */
+static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
+				      int flush_color, int work_color)
 {
-	int active = 0;
-	struct wq_barrier barr;
-
-	WARN_ON(cwq->thread == current);
+	bool wait = false;
+	unsigned int cpu;
 
-	spin_lock_irq(&cwq->lock);
-	if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
-		insert_wq_barrier(cwq, &barr, &cwq->worklist);
-		active = 1;
+	if (flush_color >= 0) {
+		BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
+		atomic_set(&wq->nr_cwqs_to_flush, 1);
 	}
-	spin_unlock_irq(&cwq->lock);
 
-	if (active) {
-		wait_for_completion(&barr.done);
-		destroy_work_on_stack(&barr.work);
+	for_each_cwq_cpu(cpu, wq) {
+		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+		struct global_cwq *gcwq = cwq->gcwq;
+
+		spin_lock_irq(&gcwq->lock);
+
+		if (flush_color >= 0) {
+			BUG_ON(cwq->flush_color != -1);
+
+			if (cwq->nr_in_flight[flush_color]) {
+				cwq->flush_color = flush_color;
+				atomic_inc(&wq->nr_cwqs_to_flush);
+				wait = true;
+			}
+		}
+
+		if (work_color >= 0) {
+			BUG_ON(work_color != work_next_color(cwq->work_color));
+			cwq->work_color = work_color;
+		}
+
+		spin_unlock_irq(&gcwq->lock);
 	}
 
-	return active;
+	if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
+		complete(&wq->first_flusher->done);
+
+	return wait;
 }
 
 /**
@@ -533,20 +2145,150 @@ static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
  *
  * We sleep until all works which were queued on entry have been handled,
  * but we are not livelocked by new incoming ones.
- *
- * This function used to run the workqueues itself.  Now we just wait for the
- * helper threads to do it.
  */
 void flush_workqueue(struct workqueue_struct *wq)
 {
-	const struct cpumask *cpu_map = wq_cpu_map(wq);
-	int cpu;
+	struct wq_flusher this_flusher = {
+		.list = LIST_HEAD_INIT(this_flusher.list),
+		.flush_color = -1,
+		.done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
+	};
+	int next_color;
 
-	might_sleep();
 	lock_map_acquire(&wq->lockdep_map);
 	lock_map_release(&wq->lockdep_map);
-	for_each_cpu(cpu, cpu_map)
-		flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
+
+	mutex_lock(&wq->flush_mutex);
+
+	/*
+	 * Start-to-wait phase
+	 */
+	next_color = work_next_color(wq->work_color);
+
+	if (next_color != wq->flush_color) {
+		/*
+		 * Color space is not full.  The current work_color
+		 * becomes our flush_color and work_color is advanced
+		 * by one.
+		 */
+		BUG_ON(!list_empty(&wq->flusher_overflow));
+		this_flusher.flush_color = wq->work_color;
+		wq->work_color = next_color;
+
+		if (!wq->first_flusher) {
+			/* no flush in progress, become the first flusher */
+			BUG_ON(wq->flush_color != this_flusher.flush_color);
+
+			wq->first_flusher = &this_flusher;
+
+			if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
+						       wq->work_color)) {
+				/* nothing to flush, done */
+				wq->flush_color = next_color;
+				wq->first_flusher = NULL;
+				goto out_unlock;
+			}
+		} else {
+			/* wait in queue */
+			BUG_ON(wq->flush_color == this_flusher.flush_color);
+			list_add_tail(&this_flusher.list, &wq->flusher_queue);
+			flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
+		}
+	} else {
+		/*
+		 * Oops, color space is full, wait on overflow queue.
+		 * The next flush completion will assign us
+		 * flush_color and transfer to flusher_queue.
+		 */
+		list_add_tail(&this_flusher.list, &wq->flusher_overflow);
+	}
+
+	mutex_unlock(&wq->flush_mutex);
+
+	wait_for_completion(&this_flusher.done);
+
+	/*
+	 * Wake-up-and-cascade phase
+	 *
+	 * First flushers are responsible for cascading flushes and
+	 * handling overflow.  Non-first flushers can simply return.
+	 */
+	if (wq->first_flusher != &this_flusher)
+		return;
+
+	mutex_lock(&wq->flush_mutex);
+
+	/* we might have raced, check again with mutex held */
+	if (wq->first_flusher != &this_flusher)
+		goto out_unlock;
+
+	wq->first_flusher = NULL;
+
+	BUG_ON(!list_empty(&this_flusher.list));
+	BUG_ON(wq->flush_color != this_flusher.flush_color);
+
+	while (true) {
+		struct wq_flusher *next, *tmp;
+
+		/* complete all the flushers sharing the current flush color */
+		list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
+			if (next->flush_color != wq->flush_color)
+				break;
+			list_del_init(&next->list);
+			complete(&next->done);
+		}
+
+		BUG_ON(!list_empty(&wq->flusher_overflow) &&
+		       wq->flush_color != work_next_color(wq->work_color));
+
+		/* this flush_color is finished, advance by one */
+		wq->flush_color = work_next_color(wq->flush_color);
+
+		/* one color has been freed, handle overflow queue */
+		if (!list_empty(&wq->flusher_overflow)) {
+			/*
+			 * Assign the same color to all overflowed
+			 * flushers, advance work_color and append to
+			 * flusher_queue.  This is the start-to-wait
+			 * phase for these overflowed flushers.
+			 */
+			list_for_each_entry(tmp, &wq->flusher_overflow, list)
+				tmp->flush_color = wq->work_color;
+
+			wq->work_color = work_next_color(wq->work_color);
+
+			list_splice_tail_init(&wq->flusher_overflow,
+					      &wq->flusher_queue);
+			flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
+		}
+
+		if (list_empty(&wq->flusher_queue)) {
+			BUG_ON(wq->flush_color != wq->work_color);
+			break;
+		}
+
+		/*
+		 * Need to flush more colors.  Make the next flusher
+		 * the new first flusher and arm cwqs.
+		 */
+		BUG_ON(wq->flush_color == wq->work_color);
+		BUG_ON(wq->flush_color != next->flush_color);
+
+		list_del_init(&next->list);
+		wq->first_flusher = next;
+
+		if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
+			break;
+
+		/*
+		 * Meh... this color is already done, clear first
+		 * flusher and repeat cascading.
+		 */
+		wq->first_flusher = NULL;
+	}
+
+out_unlock:
+	mutex_unlock(&wq->flush_mutex);
 }
 EXPORT_SYMBOL_GPL(flush_workqueue);
 
@@ -562,43 +2304,46 @@ EXPORT_SYMBOL_GPL(flush_workqueue);
  */
 int flush_work(struct work_struct *work)
 {
+	struct worker *worker = NULL;
+	struct global_cwq *gcwq;
 	struct cpu_workqueue_struct *cwq;
-	struct list_head *prev;
 	struct wq_barrier barr;
 
 	might_sleep();
-	cwq = get_wq_data(work);
-	if (!cwq)
+	gcwq = get_work_gcwq(work);
+	if (!gcwq)
 		return 0;
 
-	lock_map_acquire(&cwq->wq->lockdep_map);
-	lock_map_release(&cwq->wq->lockdep_map);
-
-	prev = NULL;
-	spin_lock_irq(&cwq->lock);
+	spin_lock_irq(&gcwq->lock);
 	if (!list_empty(&work->entry)) {
 		/*
 		 * See the comment near try_to_grab_pending()->smp_rmb().
-		 * If it was re-queued under us we are not going to wait.
+		 * If it was re-queued to a different gcwq under us, we
+		 * are not going to wait.
 		 */
 		smp_rmb();
-		if (unlikely(cwq != get_wq_data(work)))
-			goto out;
-		prev = &work->entry;
+		cwq = get_work_cwq(work);
+		if (unlikely(!cwq || gcwq != cwq->gcwq))
+			goto already_gone;
 	} else {
-		if (cwq->current_work != work)
-			goto out;
-		prev = &cwq->worklist;
+		worker = find_worker_executing_work(gcwq, work);
+		if (!worker)
+			goto already_gone;
+		cwq = worker->current_cwq;
 	}
-	insert_wq_barrier(cwq, &barr, prev->next);
-out:
-	spin_unlock_irq(&cwq->lock);
-	if (!prev)
-		return 0;
+
+	insert_wq_barrier(cwq, &barr, work, worker);
+	spin_unlock_irq(&gcwq->lock);
+
+	lock_map_acquire(&cwq->wq->lockdep_map);
+	lock_map_release(&cwq->wq->lockdep_map);
 
 	wait_for_completion(&barr.done);
 	destroy_work_on_stack(&barr.work);
 	return 1;
+already_gone:
+	spin_unlock_irq(&gcwq->lock);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(flush_work);
 
@@ -608,54 +2353,55 @@ EXPORT_SYMBOL_GPL(flush_work);
  */
 static int try_to_grab_pending(struct work_struct *work)
 {
-	struct cpu_workqueue_struct *cwq;
+	struct global_cwq *gcwq;
 	int ret = -1;
 
-	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
+	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
 		return 0;
 
 	/*
 	 * The queueing is in progress, or it is already queued. Try to
 	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
 	 */
-
-	cwq = get_wq_data(work);
-	if (!cwq)
+	gcwq = get_work_gcwq(work);
+	if (!gcwq)
 		return ret;
 
-	spin_lock_irq(&cwq->lock);
+	spin_lock_irq(&gcwq->lock);
 	if (!list_empty(&work->entry)) {
 		/*
-		 * This work is queued, but perhaps we locked the wrong cwq.
+		 * This work is queued, but perhaps we locked the wrong gcwq.
 		 * In that case we must see the new value after rmb(), see
 		 * insert_work()->wmb().
 		 */
 		smp_rmb();
-		if (cwq == get_wq_data(work)) {
+		if (gcwq == get_work_gcwq(work)) {
 			debug_work_deactivate(work);
 			list_del_init(&work->entry);
+			cwq_dec_nr_in_flight(get_work_cwq(work),
+					     get_work_color(work));
 			ret = 1;
 		}
 	}
-	spin_unlock_irq(&cwq->lock);
+	spin_unlock_irq(&gcwq->lock);
 
 	return ret;
 }
 
-static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
-				struct work_struct *work)
+static void wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
 {
 	struct wq_barrier barr;
-	int running = 0;
+	struct worker *worker;
 
-	spin_lock_irq(&cwq->lock);
-	if (unlikely(cwq->current_work == work)) {
-		insert_wq_barrier(cwq, &barr, cwq->worklist.next);
-		running = 1;
-	}
-	spin_unlock_irq(&cwq->lock);
+	spin_lock_irq(&gcwq->lock);
+
+	worker = find_worker_executing_work(gcwq, work);
+	if (unlikely(worker))
+		insert_wq_barrier(worker->current_cwq, &barr, work, worker);
 
-	if (unlikely(running)) {
+	spin_unlock_irq(&gcwq->lock);
+
+	if (unlikely(worker)) {
 		wait_for_completion(&barr.done);
 		destroy_work_on_stack(&barr.work);
 	}
@@ -663,9 +2409,6 @@ static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
 
 static void wait_on_work(struct work_struct *work)
 {
-	struct cpu_workqueue_struct *cwq;
-	struct workqueue_struct *wq;
-	const struct cpumask *cpu_map;
 	int cpu;
 
 	might_sleep();
@@ -673,15 +2416,8 @@ static void wait_on_work(struct work_struct *work)
 	lock_map_acquire(&work->lockdep_map);
 	lock_map_release(&work->lockdep_map);
 
-	cwq = get_wq_data(work);
-	if (!cwq)
-		return;
-
-	wq = cwq->wq;
-	cpu_map = wq_cpu_map(wq);
-
-	for_each_cpu(cpu, cpu_map)
-		wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
+	for_each_gcwq_cpu(cpu)
+		wait_on_cpu_work(get_gcwq(cpu), work);
 }
 
 static int __cancel_work_timer(struct work_struct *work,
@@ -696,7 +2432,7 @@ static int __cancel_work_timer(struct work_struct *work,
 		wait_on_work(work);
 	} while (unlikely(ret < 0));
 
-	clear_wq_data(work);
+	clear_work_data(work);
 	return ret;
 }
 
@@ -742,8 +2478,6 @@ int cancel_delayed_work_sync(struct delayed_work *dwork)
 }
 EXPORT_SYMBOL(cancel_delayed_work_sync);
 
-static struct workqueue_struct *keventd_wq __read_mostly;
-
 /**
  * schedule_work - put work task in global workqueue
  * @work: job to be done
@@ -757,7 +2491,7 @@ static struct workqueue_struct *keventd_wq __read_mostly;
  */
 int schedule_work(struct work_struct *work)
 {
-	return queue_work(keventd_wq, work);
+	return queue_work(system_wq, work);
 }
 EXPORT_SYMBOL(schedule_work);
 
@@ -770,7 +2504,7 @@ EXPORT_SYMBOL(schedule_work);
  */
 int schedule_work_on(int cpu, struct work_struct *work)
 {
-	return queue_work_on(cpu, keventd_wq, work);
+	return queue_work_on(cpu, system_wq, work);
 }
 EXPORT_SYMBOL(schedule_work_on);
 
@@ -785,7 +2519,7 @@ EXPORT_SYMBOL(schedule_work_on);
 int schedule_delayed_work(struct delayed_work *dwork,
 					unsigned long delay)
 {
-	return queue_delayed_work(keventd_wq, dwork, delay);
+	return queue_delayed_work(system_wq, dwork, delay);
 }
 EXPORT_SYMBOL(schedule_delayed_work);
 
@@ -798,9 +2532,8 @@ EXPORT_SYMBOL(schedule_delayed_work);
 void flush_delayed_work(struct delayed_work *dwork)
 {
 	if (del_timer_sync(&dwork->timer)) {
-		struct cpu_workqueue_struct *cwq;
-		cwq = wq_per_cpu(get_wq_data(&dwork->work)->wq, get_cpu());
-		__queue_work(cwq, &dwork->work);
+		__queue_work(get_cpu(), get_work_cwq(&dwork->work)->wq,
+			     &dwork->work);
 		put_cpu();
 	}
 	flush_work(&dwork->work);
@@ -819,7 +2552,7 @@ EXPORT_SYMBOL(flush_delayed_work);
 int schedule_delayed_work_on(int cpu,
 			struct delayed_work *dwork, unsigned long delay)
 {
-	return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
+	return queue_delayed_work_on(cpu, system_wq, dwork, delay);
 }
 EXPORT_SYMBOL(schedule_delayed_work_on);
 
@@ -835,7 +2568,6 @@ EXPORT_SYMBOL(schedule_delayed_work_on);
 int schedule_on_each_cpu(work_func_t func)
 {
 	int cpu;
-	int orig = -1;
 	struct work_struct *works;
 
 	works = alloc_percpu(struct work_struct);
@@ -844,23 +2576,12 @@ int schedule_on_each_cpu(work_func_t func)
 
 	get_online_cpus();
 
-	/*
-	 * When running in keventd don't schedule a work item on
-	 * itself.  Can just call directly because the work queue is
-	 * already bound.  This also is faster.
-	 */
-	if (current_is_keventd())
-		orig = raw_smp_processor_id();
-
 	for_each_online_cpu(cpu) {
 		struct work_struct *work = per_cpu_ptr(works, cpu);
 
 		INIT_WORK(work, func);
-		if (cpu != orig)
-			schedule_work_on(cpu, work);
+		schedule_work_on(cpu, work);
 	}
-	if (orig >= 0)
-		func(per_cpu_ptr(works, orig));
 
 	for_each_online_cpu(cpu)
 		flush_work(per_cpu_ptr(works, cpu));
@@ -896,7 +2617,7 @@ int schedule_on_each_cpu(work_func_t func)
  */
 void flush_scheduled_work(void)
 {
-	flush_workqueue(keventd_wq);
+	flush_workqueue(system_wq);
 }
 EXPORT_SYMBOL(flush_scheduled_work);
 
@@ -928,170 +2649,170 @@ EXPORT_SYMBOL_GPL(execute_in_process_context);
 
 int keventd_up(void)
 {
-	return keventd_wq != NULL;
+	return system_wq != NULL;
 }
 
-int current_is_keventd(void)
+static int alloc_cwqs(struct workqueue_struct *wq)
 {
-	struct cpu_workqueue_struct *cwq;
-	int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
-	int ret = 0;
-
-	BUG_ON(!keventd_wq);
+	/*
+	 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
+	 * Make sure that the alignment isn't lower than that of
+	 * unsigned long long.
+	 */
+	const size_t size = sizeof(struct cpu_workqueue_struct);
+	const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
+				   __alignof__(unsigned long long));
+#ifdef CONFIG_SMP
+	bool percpu = !(wq->flags & WQ_UNBOUND);
+#else
+	bool percpu = false;
+#endif
 
-	cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
-	if (current == cwq->thread)
-		ret = 1;
+	if (percpu)
+		wq->cpu_wq.pcpu = __alloc_percpu(size, align);
+	else {
+		void *ptr;
 
-	return ret;
+		/*
+		 * Allocate enough room to align cwq and put an extra
+		 * pointer at the end pointing back to the originally
+		 * allocated pointer which will be used for free.
+		 */
+		ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
+		if (ptr) {
+			wq->cpu_wq.single = PTR_ALIGN(ptr, align);
+			*(void **)(wq->cpu_wq.single + 1) = ptr;
+		}
+	}
 
+	/* just in case, make sure it's actually aligned */
+	BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
+	return wq->cpu_wq.v ? 0 : -ENOMEM;
 }
 
-static struct cpu_workqueue_struct *
-init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
+static void free_cwqs(struct workqueue_struct *wq)
 {
-	struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
-
-	cwq->wq = wq;
-	spin_lock_init(&cwq->lock);
-	INIT_LIST_HEAD(&cwq->worklist);
-	init_waitqueue_head(&cwq->more_work);
+#ifdef CONFIG_SMP
+	bool percpu = !(wq->flags & WQ_UNBOUND);
+#else
+	bool percpu = false;
+#endif
 
-	return cwq;
+	if (percpu)
+		free_percpu(wq->cpu_wq.pcpu);
+	else if (wq->cpu_wq.single) {
+		/* the pointer to free is stored right after the cwq */
+		kfree(*(void **)(wq->cpu_wq.single + 1));
+	}
 }
 
-static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
+static int wq_clamp_max_active(int max_active, unsigned int flags,
+			       const char *name)
 {
-	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
-	struct workqueue_struct *wq = cwq->wq;
-	const char *fmt = is_wq_single_threaded(wq) ? "%s" : "%s/%d";
-	struct task_struct *p;
+	int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
 
-	p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
-	/*
-	 * Nobody can add the work_struct to this cwq,
-	 *	if (caller is __create_workqueue)
-	 *		nobody should see this wq
-	 *	else // caller is CPU_UP_PREPARE
-	 *		cpu is not on cpu_online_map
-	 * so we can abort safely.
-	 */
-	if (IS_ERR(p))
-		return PTR_ERR(p);
-	if (cwq->wq->rt)
-		sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
-	cwq->thread = p;
-
-	trace_workqueue_creation(cwq->thread, cpu);
+	if (max_active < 1 || max_active > lim)
+		printk(KERN_WARNING "workqueue: max_active %d requested for %s "
+		       "is out of range, clamping between %d and %d\n",
+		       max_active, name, 1, lim);
 
-	return 0;
+	return clamp_val(max_active, 1, lim);
 }
 
-static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
+struct workqueue_struct *__alloc_workqueue_key(const char *name,
+					       unsigned int flags,
+					       int max_active,
+					       struct lock_class_key *key,
+					       const char *lock_name)
 {
-	struct task_struct *p = cwq->thread;
+	struct workqueue_struct *wq;
+	unsigned int cpu;
 
-	if (p != NULL) {
-		if (cpu >= 0)
-			kthread_bind(p, cpu);
-		wake_up_process(p);
-	}
-}
+	/*
+	 * Unbound workqueues aren't concurrency managed and should be
+	 * dispatched to workers immediately.
+	 */
+	if (flags & WQ_UNBOUND)
+		flags |= WQ_HIGHPRI;
 
-struct workqueue_struct *__create_workqueue_key(const char *name,
-						int singlethread,
-						int freezeable,
-						int rt,
-						struct lock_class_key *key,
-						const char *lock_name)
-{
-	struct workqueue_struct *wq;
-	struct cpu_workqueue_struct *cwq;
-	int err = 0, cpu;
+	max_active = max_active ?: WQ_DFL_ACTIVE;
+	max_active = wq_clamp_max_active(max_active, flags, name);
 
 	wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 	if (!wq)
-		return NULL;
+		goto err;
 
-	wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
-	if (!wq->cpu_wq) {
-		kfree(wq);
-		return NULL;
-	}
+	wq->flags = flags;
+	wq->saved_max_active = max_active;
+	mutex_init(&wq->flush_mutex);
+	atomic_set(&wq->nr_cwqs_to_flush, 0);
+	INIT_LIST_HEAD(&wq->flusher_queue);
+	INIT_LIST_HEAD(&wq->flusher_overflow);
 
 	wq->name = name;
 	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
-	wq->singlethread = singlethread;
-	wq->freezeable = freezeable;
-	wq->rt = rt;
 	INIT_LIST_HEAD(&wq->list);
 
-	if (singlethread) {
-		cwq = init_cpu_workqueue(wq, singlethread_cpu);
-		err = create_workqueue_thread(cwq, singlethread_cpu);
-		start_workqueue_thread(cwq, -1);
-	} else {
-		cpu_maps_update_begin();
-		/*
-		 * We must place this wq on list even if the code below fails.
-		 * cpu_down(cpu) can remove cpu from cpu_populated_map before
-		 * destroy_workqueue() takes the lock, in that case we leak
-		 * cwq[cpu]->thread.
-		 */
-		spin_lock(&workqueue_lock);
-		list_add(&wq->list, &workqueues);
-		spin_unlock(&workqueue_lock);
-		/*
-		 * We must initialize cwqs for each possible cpu even if we
-		 * are going to call destroy_workqueue() finally. Otherwise
-		 * cpu_up() can hit the uninitialized cwq once we drop the
-		 * lock.
-		 */
-		for_each_possible_cpu(cpu) {
-			cwq = init_cpu_workqueue(wq, cpu);
-			if (err || !cpu_online(cpu))
-				continue;
-			err = create_workqueue_thread(cwq, cpu);
-			start_workqueue_thread(cwq, cpu);
-		}
-		cpu_maps_update_done();
+	if (alloc_cwqs(wq) < 0)
+		goto err;
+
+	for_each_cwq_cpu(cpu, wq) {
+		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+		struct global_cwq *gcwq = get_gcwq(cpu);
+
+		BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
+		cwq->gcwq = gcwq;
+		cwq->wq = wq;
+		cwq->flush_color = -1;
+		cwq->max_active = max_active;
+		INIT_LIST_HEAD(&cwq->delayed_works);
 	}
 
-	if (err) {
-		destroy_workqueue(wq);
-		wq = NULL;
+	if (flags & WQ_RESCUER) {
+		struct worker *rescuer;
+
+		if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
+			goto err;
+
+		wq->rescuer = rescuer = alloc_worker();
+		if (!rescuer)
+			goto err;
+
+		rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
+		if (IS_ERR(rescuer->task))
+			goto err;
+
+		wq->rescuer = rescuer;
+		rescuer->task->flags |= PF_THREAD_BOUND;
+		wake_up_process(rescuer->task);
 	}
-	return wq;
-}
-EXPORT_SYMBOL_GPL(__create_workqueue_key);
 
-static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
-{
 	/*
-	 * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
-	 * cpu_add_remove_lock protects cwq->thread.
+	 * workqueue_lock protects global freeze state and workqueues
+	 * list.  Grab it, set max_active accordingly and add the new
+	 * workqueue to workqueues list.
 	 */
-	if (cwq->thread == NULL)
-		return;
+	spin_lock(&workqueue_lock);
 
-	lock_map_acquire(&cwq->wq->lockdep_map);
-	lock_map_release(&cwq->wq->lockdep_map);
+	if (workqueue_freezing && wq->flags & WQ_FREEZEABLE)
+		for_each_cwq_cpu(cpu, wq)
+			get_cwq(cpu, wq)->max_active = 0;
 
-	flush_cpu_workqueue(cwq);
-	/*
-	 * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,
-	 * a concurrent flush_workqueue() can insert a barrier after us.
-	 * However, in that case run_workqueue() won't return and check
-	 * kthread_should_stop() until it flushes all work_struct's.
-	 * When ->worklist becomes empty it is safe to exit because no
-	 * more work_structs can be queued on this cwq: flush_workqueue
-	 * checks list_empty(), and a "normal" queue_work() can't use
-	 * a dead CPU.
-	 */
-	trace_workqueue_destruction(cwq->thread);
-	kthread_stop(cwq->thread);
-	cwq->thread = NULL;
+	list_add(&wq->list, &workqueues);
+
+	spin_unlock(&workqueue_lock);
+
+	return wq;
+err:
+	if (wq) {
+		free_cwqs(wq);
+		free_mayday_mask(wq->mayday_mask);
+		kfree(wq->rescuer);
+		kfree(wq);
+	}
+	return NULL;
 }
+EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
 
 /**
  * destroy_workqueue - safely terminate a workqueue
@@ -1101,72 +2822,516 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
  */
 void destroy_workqueue(struct workqueue_struct *wq)
 {
-	const struct cpumask *cpu_map = wq_cpu_map(wq);
-	int cpu;
+	unsigned int cpu;
+
+	flush_workqueue(wq);
 
-	cpu_maps_update_begin();
+	/*
+	 * wq list is used to freeze wq, remove from list after
+	 * flushing is complete in case freeze races us.
+	 */
 	spin_lock(&workqueue_lock);
 	list_del(&wq->list);
 	spin_unlock(&workqueue_lock);
 
-	for_each_cpu(cpu, cpu_map)
-		cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
- 	cpu_maps_update_done();
+	/* sanity check */
+	for_each_cwq_cpu(cpu, wq) {
+		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+		int i;
+
+		for (i = 0; i < WORK_NR_COLORS; i++)
+			BUG_ON(cwq->nr_in_flight[i]);
+		BUG_ON(cwq->nr_active);
+		BUG_ON(!list_empty(&cwq->delayed_works));
+	}
+
+	if (wq->flags & WQ_RESCUER) {
+		kthread_stop(wq->rescuer->task);
+		free_mayday_mask(wq->mayday_mask);
+	}
 
-	free_percpu(wq->cpu_wq);
+	free_cwqs(wq);
 	kfree(wq);
 }
 EXPORT_SYMBOL_GPL(destroy_workqueue);
 
+/**
+ * workqueue_set_max_active - adjust max_active of a workqueue
+ * @wq: target workqueue
+ * @max_active: new max_active value.
+ *
+ * Set max_active of @wq to @max_active.
+ *
+ * CONTEXT:
+ * Don't call from IRQ context.
+ */
+void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
+{
+	unsigned int cpu;
+
+	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
+
+	spin_lock(&workqueue_lock);
+
+	wq->saved_max_active = max_active;
+
+	for_each_cwq_cpu(cpu, wq) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+
+		spin_lock_irq(&gcwq->lock);
+
+		if (!(wq->flags & WQ_FREEZEABLE) ||
+		    !(gcwq->flags & GCWQ_FREEZING))
+			get_cwq(gcwq->cpu, wq)->max_active = max_active;
+
+		spin_unlock_irq(&gcwq->lock);
+	}
+
+	spin_unlock(&workqueue_lock);
+}
+EXPORT_SYMBOL_GPL(workqueue_set_max_active);
+
+/**
+ * workqueue_congested - test whether a workqueue is congested
+ * @cpu: CPU in question
+ * @wq: target workqueue
+ *
+ * Test whether @wq's cpu workqueue for @cpu is congested.  There is
+ * no synchronization around this function and the test result is
+ * unreliable and only useful as advisory hints or for debugging.
+ *
+ * RETURNS:
+ * %true if congested, %false otherwise.
+ */
+bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
+{
+	struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+	return !list_empty(&cwq->delayed_works);
+}
+EXPORT_SYMBOL_GPL(workqueue_congested);
+
+/**
+ * work_cpu - return the last known associated cpu for @work
+ * @work: the work of interest
+ *
+ * RETURNS:
+ * CPU number if @work was ever queued.  WORK_CPU_NONE otherwise.
+ */
+unsigned int work_cpu(struct work_struct *work)
+{
+	struct global_cwq *gcwq = get_work_gcwq(work);
+
+	return gcwq ? gcwq->cpu : WORK_CPU_NONE;
+}
+EXPORT_SYMBOL_GPL(work_cpu);
+
+/**
+ * work_busy - test whether a work is currently pending or running
+ * @work: the work to be tested
+ *
+ * Test whether @work is currently pending or running.  There is no
+ * synchronization around this function and the test result is
+ * unreliable and only useful as advisory hints or for debugging.
+ * Especially for reentrant wqs, the pending state might hide the
+ * running state.
+ *
+ * RETURNS:
+ * OR'd bitmask of WORK_BUSY_* bits.
+ */
+unsigned int work_busy(struct work_struct *work)
+{
+	struct global_cwq *gcwq = get_work_gcwq(work);
+	unsigned long flags;
+	unsigned int ret = 0;
+
+	if (!gcwq)
+		return false;
+
+	spin_lock_irqsave(&gcwq->lock, flags);
+
+	if (work_pending(work))
+		ret |= WORK_BUSY_PENDING;
+	if (find_worker_executing_work(gcwq, work))
+		ret |= WORK_BUSY_RUNNING;
+
+	spin_unlock_irqrestore(&gcwq->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(work_busy);
+
+/*
+ * CPU hotplug.
+ *
+ * There are two challenges in supporting CPU hotplug.  Firstly, there
+ * are a lot of assumptions on strong associations among work, cwq and
+ * gcwq which make migrating pending and scheduled works very
+ * difficult to implement without impacting hot paths.  Secondly,
+ * 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 --------------
+ */
+
+/**
+ * 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)
+{
+	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());
+
+	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;
+
+	/*
+	 * 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);
+
+	/*
+	 * 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);
+
+	spin_unlock_irq(&gcwq->lock);
+	del_timer_sync(&gcwq->idle_timer);
+	spin_lock_irq(&gcwq->lock);
+
+	/*
+	 * 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);
+
+	/*
+	 * 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 freezeable cwqs.  Don't declare
+	 * completion while frozen.
+	 */
+	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++;
+		}
+
+		list_for_each_entry(worker, &gcwq->idle_list, entry) {
+			if (!nr_works--)
+				break;
+			wake_up_process(worker->task);
+		}
+
+		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);
+			}
+		}
+
+		/* give a breather */
+		if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
+			break;
+	}
+
+	/*
+	 * 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.
+	 */
+	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);
+
+	/*
+	 * 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.
+	 */
+	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;
+}
+
+/**
+ * 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.
+ */
+static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
+{
+	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)
 {
 	unsigned int cpu = (unsigned long)hcpu;
-	struct cpu_workqueue_struct *cwq;
-	struct workqueue_struct *wq;
-	int err = 0;
+	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;
 
 	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 */
 	case CPU_UP_PREPARE:
-		cpumask_set_cpu(cpu, cpu_populated_map);
-	}
-undo:
-	list_for_each_entry(wq, &workqueues, list) {
-		cwq = per_cpu_ptr(wq->cpu_wq, cpu);
-
-		switch (action) {
-		case CPU_UP_PREPARE:
-			err = create_workqueue_thread(cwq, cpu);
-			if (!err)
-				break;
-			printk(KERN_ERR "workqueue [%s] for %i failed\n",
-				wq->name, cpu);
-			action = CPU_UP_CANCELED;
-			err = -ENOMEM;
-			goto undo;
-
-		case CPU_ONLINE:
-			start_workqueue_thread(cwq, cpu);
-			break;
-
-		case CPU_UP_CANCELED:
-			start_workqueue_thread(cwq, -1);
-		case CPU_POST_DEAD:
-			cleanup_workqueue_thread(cwq);
-			break;
+		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);
+
 	switch (action) {
-	case CPU_UP_CANCELED:
+	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;
+
+	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;
+
 	case CPU_POST_DEAD:
-		cpumask_clear_cpu(cpu, cpu_populated_map);
+		gcwq->trustee_state = TRUSTEE_BUTCHER;
+		/* fall through */
+	case CPU_UP_CANCELED:
+		destroy_worker(gcwq->first_idle);
+		gcwq->first_idle = NULL;
+		break;
+
+	case CPU_DOWN_FAILED:
+	case CPU_ONLINE:
+		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;
+		break;
 	}
 
-	return notifier_from_errno(err);
+	spin_unlock_irqrestore(&gcwq->lock, flags);
+
+	return notifier_from_errno(0);
 }
 
 #ifdef CONFIG_SMP
@@ -1216,14 +3381,199 @@ long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
 EXPORT_SYMBOL_GPL(work_on_cpu);
 #endif /* CONFIG_SMP */
 
-void __init init_workqueues(void)
+#ifdef CONFIG_FREEZER
+
+/**
+ * freeze_workqueues_begin - begin freezing workqueues
+ *
+ * Start freezing workqueues.  After this function returns, all
+ * freezeable workqueues will queue new works to their frozen_works
+ * list instead of gcwq->worklist.
+ *
+ * CONTEXT:
+ * Grabs and releases workqueue_lock and gcwq->lock's.
+ */
+void freeze_workqueues_begin(void)
+{
+	unsigned int cpu;
+
+	spin_lock(&workqueue_lock);
+
+	BUG_ON(workqueue_freezing);
+	workqueue_freezing = true;
+
+	for_each_gcwq_cpu(cpu) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct workqueue_struct *wq;
+
+		spin_lock_irq(&gcwq->lock);
+
+		BUG_ON(gcwq->flags & GCWQ_FREEZING);
+		gcwq->flags |= GCWQ_FREEZING;
+
+		list_for_each_entry(wq, &workqueues, list) {
+			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+			if (cwq && wq->flags & WQ_FREEZEABLE)
+				cwq->max_active = 0;
+		}
+
+		spin_unlock_irq(&gcwq->lock);
+	}
+
+	spin_unlock(&workqueue_lock);
+}
+
+/**
+ * freeze_workqueues_busy - are freezeable workqueues still busy?
+ *
+ * Check whether freezing is complete.  This function must be called
+ * between freeze_workqueues_begin() and thaw_workqueues().
+ *
+ * CONTEXT:
+ * Grabs and releases workqueue_lock.
+ *
+ * RETURNS:
+ * %true if some freezeable workqueues are still busy.  %false if
+ * freezing is complete.
+ */
+bool freeze_workqueues_busy(void)
+{
+	unsigned int cpu;
+	bool busy = false;
+
+	spin_lock(&workqueue_lock);
+
+	BUG_ON(!workqueue_freezing);
+
+	for_each_gcwq_cpu(cpu) {
+		struct workqueue_struct *wq;
+		/*
+		 * nr_active is monotonically decreasing.  It's safe
+		 * to peek without lock.
+		 */
+		list_for_each_entry(wq, &workqueues, list) {
+			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+			if (!cwq || !(wq->flags & WQ_FREEZEABLE))
+				continue;
+
+			BUG_ON(cwq->nr_active < 0);
+			if (cwq->nr_active) {
+				busy = true;
+				goto out_unlock;
+			}
+		}
+	}
+out_unlock:
+	spin_unlock(&workqueue_lock);
+	return busy;
+}
+
+/**
+ * thaw_workqueues - thaw workqueues
+ *
+ * Thaw workqueues.  Normal queueing is restored and all collected
+ * frozen works are transferred to their respective gcwq worklists.
+ *
+ * CONTEXT:
+ * Grabs and releases workqueue_lock and gcwq->lock's.
+ */
+void thaw_workqueues(void)
+{
+	unsigned int cpu;
+
+	spin_lock(&workqueue_lock);
+
+	if (!workqueue_freezing)
+		goto out_unlock;
+
+	for_each_gcwq_cpu(cpu) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct workqueue_struct *wq;
+
+		spin_lock_irq(&gcwq->lock);
+
+		BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
+		gcwq->flags &= ~GCWQ_FREEZING;
+
+		list_for_each_entry(wq, &workqueues, list) {
+			struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+			if (!cwq || !(wq->flags & WQ_FREEZEABLE))
+				continue;
+
+			/* restore max_active and repopulate worklist */
+			cwq->max_active = wq->saved_max_active;
+
+			while (!list_empty(&cwq->delayed_works) &&
+			       cwq->nr_active < cwq->max_active)
+				cwq_activate_first_delayed(cwq);
+		}
+
+		wake_up_worker(gcwq);
+
+		spin_unlock_irq(&gcwq->lock);
+	}
+
+	workqueue_freezing = false;
+out_unlock:
+	spin_unlock(&workqueue_lock);
+}
+#endif /* CONFIG_FREEZER */
+
+static int __init init_workqueues(void)
 {
-	alloc_cpumask_var(&cpu_populated_map, GFP_KERNEL);
+	unsigned int cpu;
+	int i;
+
+	hotcpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
+
+	/* initialize gcwqs */
+	for_each_gcwq_cpu(cpu) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+
+		spin_lock_init(&gcwq->lock);
+		INIT_LIST_HEAD(&gcwq->worklist);
+		gcwq->cpu = cpu;
+		if (cpu == WORK_CPU_UNBOUND)
+			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;
+
+		setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
+			    (unsigned long)gcwq);
 
-	cpumask_copy(cpu_populated_map, cpu_online_mask);
-	singlethread_cpu = cpumask_first(cpu_possible_mask);
-	cpu_singlethread_map = cpumask_of(singlethread_cpu);
-	hotcpu_notifier(workqueue_cpu_callback, 0);
-	keventd_wq = create_workqueue("events");
-	BUG_ON(!keventd_wq);
+		ida_init(&gcwq->worker_ida);
+
+		gcwq->trustee_state = TRUSTEE_DONE;
+		init_waitqueue_head(&gcwq->trustee_wait);
+	}
+
+	/* create the initial worker */
+	for_each_online_gcwq_cpu(cpu) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct worker *worker;
+
+		worker = create_worker(gcwq, true);
+		BUG_ON(!worker);
+		spin_lock_irq(&gcwq->lock);
+		start_worker(worker);
+		spin_unlock_irq(&gcwq->lock);
+	}
+
+	system_wq = alloc_workqueue("events", 0, 0);
+	system_long_wq = alloc_workqueue("events_long", 0, 0);
+	system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
+	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
+					    WQ_UNBOUND_MAX_ACTIVE);
+	BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq);
+	return 0;
 }
+early_initcall(init_workqueues);