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 59fef1531dd..9ca34cddaf6 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);