1 files changed, 319 insertions, 139 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f77afd939229..0400553f0d04 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -42,9 +42,6 @@
 #include <linux/lockdep.h>
 #include <linux/idr.h>
 
-#define CREATE_TRACE_POINTS
-#include <trace/events/workqueue.h>
-
 #include "workqueue_sched.h"
 
 enum {
@@ -82,7 +79,9 @@ enum {
         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_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
+                                                /* call for help after 10ms
+                                                   (min two ticks) */
         MAYDAY_INTERVAL         = HZ / 10,      /* and then every 100ms */
         CREATE_COOLDOWN         = HZ,           /* time to breath after fail */
         TRUSTEE_COOLDOWN        = HZ / 10,      /* for trustee draining */
@@ -252,10 +251,15 @@ 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;
+struct workqueue_struct *system_freezable_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);
+EXPORT_SYMBOL_GPL(system_freezable_wq);
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/workqueue.h>
 
 #define for_each_busy_worker(worker, i, pos, gcwq)                      \
         for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)                     \
@@ -310,25 +314,15 @@ static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
              (cpu) < WORK_CPU_NONE;                                     \
              (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
 
-#ifdef CONFIG_LOCKDEP
-/**
- * in_workqueue_context() - in context of specified workqueue?
- * @wq: the workqueue of interest
- *
- * Checks lockdep state to see if the current task is executing from
- * within a workqueue item.  This function exists only if lockdep is
- * enabled.
- */
-int in_workqueue_context(struct workqueue_struct *wq)
-{
-        return lock_is_held(&wq->lockdep_map);
-}
-#endif
-
 #ifdef CONFIG_DEBUG_OBJECTS_WORK
 
 static struct debug_obj_descr work_debug_descr;
 
+static void *work_debug_hint(void *addr)
+{
+        return ((struct work_struct *) addr)->func;
+}
+
 /*
  * fixup_init is called when:
  * - an active object is initialized
@@ -400,6 +394,7 @@ static int work_fixup_free(void *addr, enum debug_obj_state state)
 
 static struct debug_obj_descr work_debug_descr = {
         .name           = "work_struct",
+        .debug_hint     = work_debug_hint,
         .fixup_init     = work_fixup_init,
         .fixup_activate = work_fixup_activate,
         .fixup_free     = work_fixup_free,
@@ -604,7 +599,9 @@ 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;
+        return !list_empty(&gcwq->worklist) &&
+                (atomic_read(nr_running) <= 1 ||
+                 gcwq->flags & GCWQ_HIGHPRI_PENDING);
 }
 
 /* Do we need a new worker?  Called from manager. */
@@ -674,7 +671,7 @@ 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)))
+        if (!(worker->flags & WORKER_NOT_RUNNING))
                 atomic_inc(get_gcwq_nr_running(cpu));
 }
 
@@ -700,7 +697,7 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
         struct global_cwq *gcwq = get_gcwq(cpu);
         atomic_t *nr_running = get_gcwq_nr_running(cpu);
 
-        if (unlikely(worker->flags & WORKER_NOT_RUNNING))
+        if (worker->flags & WORKER_NOT_RUNNING)
                 return NULL;
 
         /* this can only happen on the local cpu */
@@ -781,7 +778,11 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
 
         worker->flags &= ~flags;
 
-        /* if transitioning out of NOT_RUNNING, increment nr_running */
+        /*
+         * If transitioning out of NOT_RUNNING, increment nr_running.  Note
+         * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
+         * of multiple flags, not a single flag.
+         */
         if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
                 if (!(worker->flags & WORKER_NOT_RUNNING))
                         atomic_inc(get_gcwq_nr_running(gcwq->cpu));
@@ -945,6 +946,38 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
                 wake_up_worker(gcwq);
 }
 
+/*
+ * Test whether @work is being queued from another work executing on the
+ * same workqueue.  This is rather expensive and should only be used from
+ * cold paths.
+ */
+static bool is_chained_work(struct workqueue_struct *wq)
+{
+        unsigned long flags;
+        unsigned int cpu;
+
+        for_each_gcwq_cpu(cpu) {
+                struct global_cwq *gcwq = get_gcwq(cpu);
+                struct worker *worker;
+                struct hlist_node *pos;
+                int i;
+
+                spin_lock_irqsave(&gcwq->lock, flags);
+                for_each_busy_worker(worker, i, pos, gcwq) {
+                        if (worker->task != current)
+                                continue;
+                        spin_unlock_irqrestore(&gcwq->lock, flags);
+                        /*
+                         * I'm @worker, no locking necessary.  See if @work
+                         * is headed to the same workqueue.
+                         */
+                        return worker->current_cwq->wq == wq;
+                }
+                spin_unlock_irqrestore(&gcwq->lock, flags);
+        }
+        return false;
+}
+
 static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
                          struct work_struct *work)
 {
@@ -956,7 +989,9 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 
         debug_work_activate(work);
 
-        if (WARN_ON_ONCE(wq->flags & WQ_DYING))
+        /* if dying, only works from the same workqueue are allowed */
+        if (unlikely(wq->flags & WQ_DYING) &&
+            WARN_ON_ONCE(!is_chained_work(wq)))
                 return;
 
         /* determine gcwq to use */
@@ -997,6 +1032,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 
         /* gcwq determined, get cwq and queue */
         cwq = get_cwq(gcwq->cpu, wq);
+        trace_workqueue_queue_work(cpu, cwq, work);
 
         BUG_ON(!list_empty(&work->entry));
 
@@ -1004,6 +1040,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
         work_flags = work_color_to_flags(cwq->work_color);
 
         if (likely(cwq->nr_active < cwq->max_active)) {
+                trace_workqueue_activate_work(work);
                 cwq->nr_active++;
                 worklist = gcwq_determine_ins_pos(gcwq, cwq);
         } else {
@@ -1254,8 +1291,14 @@ __acquires(&gcwq->lock)
                         return true;
                 spin_unlock_irq(&gcwq->lock);
 
-                /* CPU has come up inbetween, retry migration */
+                /*
+                 * We've raced with CPU hot[un]plug.  Give it a breather
+                 * and retry migration.  cond_resched() is required here;
+                 * otherwise, we might deadlock against cpu_stop trying to
+                 * bring down the CPU on non-preemptive kernel.
+                 */
                 cpu_relax();
+                cond_resched();
         }
 }
 
@@ -1329,8 +1372,10 @@ static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
         worker->id = id;
 
         if (!on_unbound_cpu)
-                worker->task = kthread_create(worker_thread, worker,
-                                              "kworker/%u:%d", gcwq->cpu, id);
+                worker->task = kthread_create_on_node(worker_thread,
+                                                      worker,
+                                                      cpu_to_node(gcwq->cpu),
+                                                      "kworker/%u:%d", gcwq->cpu, id);
         else
                 worker->task = kthread_create(worker_thread, worker,
                                               "kworker/u:%d", id);
@@ -1679,6 +1724,7 @@ static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
                                                     struct work_struct, entry);
         struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
 
+        trace_workqueue_activate_work(work);
         move_linked_works(work, pos, NULL);
         __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
         cwq->nr_active++;
@@ -1816,7 +1862,7 @@ __acquires(&gcwq->lock)
         spin_unlock_irq(&gcwq->lock);
 
         work_clear_pending(work);
-        lock_map_acquire(&cwq->wq->lockdep_map);
+        lock_map_acquire_read(&cwq->wq->lockdep_map);
         lock_map_acquire(&lockdep_map);
         trace_workqueue_execute_start(work);
         f(work);
@@ -2019,6 +2065,15 @@ repeat:
                                 move_linked_works(work, scheduled, &n);
 
                 process_scheduled_works(rescuer);
+
+                /*
+                 * Leave this gcwq.  If keep_working() is %true, notify a
+                 * regular worker; otherwise, we end up with 0 concurrency
+                 * and stalling the execution.
+                 */
+                if (keep_working(gcwq))
+                        wake_up_worker(gcwq);
+
                 spin_unlock_irq(&gcwq->lock);
         }
 
@@ -2074,7 +2129,7 @@ static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
          * checks and call back into the fixup functions where we
          * might deadlock.
          */
-        INIT_WORK_ON_STACK(&barr->work, wq_barrier_func);
+        INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
         __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
         init_completion(&barr->done);
 
@@ -2326,27 +2381,17 @@ out_unlock:
 }
 EXPORT_SYMBOL_GPL(flush_workqueue);
 
-/**
- * flush_work - block until a work_struct's callback has terminated
- * @work: the work which is to be flushed
- *
- * Returns false if @work has already terminated.
- *
- * It is expected that, prior to calling flush_work(), the caller has
- * arranged for the work to not be requeued, otherwise it doesn't make
- * sense to use this function.
- */
-int flush_work(struct work_struct *work)
+static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
+                             bool wait_executing)
 {
         struct worker *worker = NULL;
         struct global_cwq *gcwq;
         struct cpu_workqueue_struct *cwq;
-        struct wq_barrier barr;
 
         might_sleep();
         gcwq = get_work_gcwq(work);
         if (!gcwq)
-                return 0;
+                return false;
 
         spin_lock_irq(&gcwq->lock);
         if (!list_empty(&work->entry)) {
@@ -2359,28 +2404,137 @@ int flush_work(struct work_struct *work)
                 cwq = get_work_cwq(work);
                 if (unlikely(!cwq || gcwq != cwq->gcwq))
                         goto already_gone;
-        } else {
+        } else if (wait_executing) {
                 worker = find_worker_executing_work(gcwq, work);
                 if (!worker)
                         goto already_gone;
                 cwq = worker->current_cwq;
-        }
+        } else
+                goto already_gone;
 
-        insert_wq_barrier(cwq, &barr, work, worker);
+        insert_wq_barrier(cwq, barr, work, worker);
         spin_unlock_irq(&gcwq->lock);
 
-        lock_map_acquire(&cwq->wq->lockdep_map);
+        /*
+         * If @max_active is 1 or rescuer is in use, flushing another work
+         * item on the same workqueue may lead to deadlock.  Make sure the
+         * flusher is not running on the same workqueue by verifying write
+         * access.
+         */
+        if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
+                lock_map_acquire(&cwq->wq->lockdep_map);
+        else
+                lock_map_acquire_read(&cwq->wq->lockdep_map);
         lock_map_release(&cwq->wq->lockdep_map);
 
-        wait_for_completion(&barr.done);
-        destroy_work_on_stack(&barr.work);
-        return 1;
+        return true;
 already_gone:
         spin_unlock_irq(&gcwq->lock);
-        return 0;
+        return false;
+}
+
+/**
+ * flush_work - wait for a work to finish executing the last queueing instance
+ * @work: the work to flush
+ *
+ * Wait until @work has finished execution.  This function considers
+ * only the last queueing instance of @work.  If @work has been
+ * enqueued across different CPUs on a non-reentrant workqueue or on
+ * multiple workqueues, @work might still be executing on return on
+ * some of the CPUs from earlier queueing.
+ *
+ * If @work was queued only on a non-reentrant, ordered or unbound
+ * workqueue, @work is guaranteed to be idle on return if it hasn't
+ * been requeued since flush started.
+ *
+ * RETURNS:
+ * %true if flush_work() waited for the work to finish execution,
+ * %false if it was already idle.
+ */
+bool flush_work(struct work_struct *work)
+{
+        struct wq_barrier barr;
+
+        if (start_flush_work(work, &barr, true)) {
+                wait_for_completion(&barr.done);
+                destroy_work_on_stack(&barr.work);
+                return true;
+        } else
+                return false;
 }
 EXPORT_SYMBOL_GPL(flush_work);
 
+static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
+{
+        struct wq_barrier barr;
+        struct worker *worker;
+
+        spin_lock_irq(&gcwq->lock);
+
+        worker = find_worker_executing_work(gcwq, work);
+        if (unlikely(worker))
+                insert_wq_barrier(worker->current_cwq, &barr, work, worker);
+
+        spin_unlock_irq(&gcwq->lock);
+
+        if (unlikely(worker)) {
+                wait_for_completion(&barr.done);
+                destroy_work_on_stack(&barr.work);
+                return true;
+        } else
+                return false;
+}
+
+static bool wait_on_work(struct work_struct *work)
+{
+        bool ret = false;
+        int cpu;
+
+        might_sleep();
+
+        lock_map_acquire(&work->lockdep_map);
+        lock_map_release(&work->lockdep_map);
+
+        for_each_gcwq_cpu(cpu)
+                ret |= wait_on_cpu_work(get_gcwq(cpu), work);
+        return ret;
+}
+
+/**
+ * flush_work_sync - wait until a work has finished execution
+ * @work: the work to flush
+ *
+ * Wait until @work has finished execution.  On return, it's
+ * guaranteed that all queueing instances of @work which happened
+ * before this function is called are finished.  In other words, if
+ * @work hasn't been requeued since this function was called, @work is
+ * guaranteed to be idle on return.
+ *
+ * RETURNS:
+ * %true if flush_work_sync() waited for the work to finish execution,
+ * %false if it was already idle.
+ */
+bool flush_work_sync(struct work_struct *work)
+{
+        struct wq_barrier barr;
+        bool pending, waited;
+
+        /* we'll wait for executions separately, queue barr only if pending */
+        pending = start_flush_work(work, &barr, false);
+
+        /* wait for executions to finish */
+        waited = wait_on_work(work);
+
+        /* wait for the pending one */
+        if (pending) {
+                wait_for_completion(&barr.done);
+                destroy_work_on_stack(&barr.work);
+        }
+
+        return pending || waited;
+}
+EXPORT_SYMBOL_GPL(flush_work_sync);
+
 /*
  * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
  * so this work can't be re-armed in any way.
@@ -2423,39 +2577,7 @@ static int try_to_grab_pending(struct work_struct *work)
         return ret;
 }
 
-static void wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
-{
-        struct wq_barrier barr;
-        struct worker *worker;
-
-        spin_lock_irq(&gcwq->lock);
-
-        worker = find_worker_executing_work(gcwq, work);
-        if (unlikely(worker))
-                insert_wq_barrier(worker->current_cwq, &barr, work, worker);
-
-        spin_unlock_irq(&gcwq->lock);
-
-        if (unlikely(worker)) {
-                wait_for_completion(&barr.done);
-                destroy_work_on_stack(&barr.work);
-        }
-}
-
-static void wait_on_work(struct work_struct *work)
-{
-        int cpu;
-
-        might_sleep();
-
-        lock_map_acquire(&work->lockdep_map);
-        lock_map_release(&work->lockdep_map);
-
-        for_each_gcwq_cpu(cpu)
-                wait_on_cpu_work(get_gcwq(cpu), work);
-}
-
-static int __cancel_work_timer(struct work_struct *work,
+static bool __cancel_work_timer(struct work_struct *work,
                                 struct timer_list* timer)
 {
         int ret;
@@ -2472,42 +2594,81 @@ static int __cancel_work_timer(struct work_struct *work,
 }
 
 /**
- * cancel_work_sync - block until a work_struct's callback has terminated
- * @work: the work which is to be flushed
+ * cancel_work_sync - cancel a work and wait for it to finish
+ * @work: the work to cancel
  *
- * Returns true if @work was pending.
- *
- * cancel_work_sync() will cancel the work if it is queued. If the work's
- * callback appears to be running, cancel_work_sync() will block until it
- * has completed.
- *
- * It is possible to use this function if the work re-queues itself. It can
- * cancel the work even if it migrates to another workqueue, however in that
- * case it only guarantees that work->func() has completed on the last queued
- * workqueue.
+ * Cancel @work and wait for its execution to finish.  This function
+ * can be used even if the work re-queues itself or migrates to
+ * another workqueue.  On return from this function, @work is
+ * guaranteed to be not pending or executing on any CPU.
  *
- * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
- * pending, otherwise it goes into a busy-wait loop until the timer expires.
+ * cancel_work_sync(&delayed_work->work) must not be used for
+ * delayed_work's.  Use cancel_delayed_work_sync() instead.
  *
- * The caller must ensure that workqueue_struct on which this work was last
+ * The caller must ensure that the workqueue on which @work was last
  * queued can't be destroyed before this function returns.
+ *
+ * RETURNS:
+ * %true if @work was pending, %false otherwise.
  */
-int cancel_work_sync(struct work_struct *work)
+bool cancel_work_sync(struct work_struct *work)
 {
         return __cancel_work_timer(work, NULL);
 }
 EXPORT_SYMBOL_GPL(cancel_work_sync);
 
 /**
- * cancel_delayed_work_sync - reliably kill off a delayed work.
- * @dwork: the delayed work struct
+ * flush_delayed_work - wait for a dwork to finish executing the last queueing
+ * @dwork: the delayed work to flush
+ *
+ * Delayed timer is cancelled and the pending work is queued for
+ * immediate execution.  Like flush_work(), this function only
+ * considers the last queueing instance of @dwork.
+ *
+ * RETURNS:
+ * %true if flush_work() waited for the work to finish execution,
+ * %false if it was already idle.
+ */
+bool flush_delayed_work(struct delayed_work *dwork)
+{
+        if (del_timer_sync(&dwork->timer))
+                __queue_work(raw_smp_processor_id(),
+                             get_work_cwq(&dwork->work)->wq, &dwork->work);
+        return flush_work(&dwork->work);
+}
+EXPORT_SYMBOL(flush_delayed_work);
+
+/**
+ * flush_delayed_work_sync - wait for a dwork to finish
+ * @dwork: the delayed work to flush
+ *
+ * Delayed timer is cancelled and the pending work is queued for
+ * execution immediately.  Other than timer handling, its behavior
+ * is identical to flush_work_sync().
+ *
+ * RETURNS:
+ * %true if flush_work_sync() waited for the work to finish execution,
+ * %false if it was already idle.
+ */
+bool flush_delayed_work_sync(struct delayed_work *dwork)
+{
+        if (del_timer_sync(&dwork->timer))
+                __queue_work(raw_smp_processor_id(),
+                             get_work_cwq(&dwork->work)->wq, &dwork->work);
+        return flush_work_sync(&dwork->work);
+}
+EXPORT_SYMBOL(flush_delayed_work_sync);
+
+/**
+ * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
+ * @dwork: the delayed work cancel
  *
- * Returns true if @dwork was pending.
+ * This is cancel_work_sync() for delayed works.
  *
- * It is possible to use this function if @dwork rearms itself via queue_work()
- * or queue_delayed_work(). See also the comment for cancel_work_sync().
+ * RETURNS:
+ * %true if @dwork was pending, %false otherwise.
  */
-int cancel_delayed_work_sync(struct delayed_work *dwork)
+bool cancel_delayed_work_sync(struct delayed_work *dwork)
 {
         return __cancel_work_timer(&dwork->work, &dwork->timer);
 }
@@ -2559,23 +2720,6 @@ int schedule_delayed_work(struct delayed_work *dwork,
 EXPORT_SYMBOL(schedule_delayed_work);
 
 /**
- * flush_delayed_work - block until a dwork_struct's callback has terminated
- * @dwork: the delayed work which is to be flushed
- *
- * Any timeout is cancelled, and any pending work is run immediately.
- */
-void flush_delayed_work(struct delayed_work *dwork)
-{
-        if (del_timer_sync(&dwork->timer)) {
-                __queue_work(get_cpu(), get_work_cwq(&dwork->work)->wq,
-                             &dwork->work);
-                put_cpu();
-        }
-        flush_work(&dwork->work);
-}
-EXPORT_SYMBOL(flush_delayed_work);
-
-/**
  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
  * @cpu: cpu to use
  * @dwork: job to be done
@@ -2592,13 +2736,15 @@ int schedule_delayed_work_on(int cpu,
 EXPORT_SYMBOL(schedule_delayed_work_on);
 
 /**
- * schedule_on_each_cpu - call a function on each online CPU from keventd
+ * schedule_on_each_cpu - execute a function synchronously on each online CPU
  * @func: the function to call
  *
- * Returns zero on success.
- * Returns -ve errno on failure.
- *
+ * schedule_on_each_cpu() executes @func on each online CPU using the
+ * system workqueue and blocks until all CPUs have completed.
  * schedule_on_each_cpu() is very slow.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
  */
 int schedule_on_each_cpu(work_func_t func)
 {
@@ -2764,6 +2910,13 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name,
         unsigned int cpu;
 
         /*
+         * Workqueues which may be used during memory reclaim should
+         * have a rescuer to guarantee forward progress.
+         */
+        if (flags & WQ_MEM_RECLAIM)
+                flags |= WQ_RESCUER;
+
+        /*
          * Unbound workqueues aren't concurrency managed and should be
          * dispatched to workers immediately.
          */
@@ -2828,7 +2981,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *name,
          */
         spin_lock(&workqueue_lock);
 
-        if (workqueue_freezing && wq->flags & WQ_FREEZEABLE)
+        if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
                 for_each_cwq_cpu(cpu, wq)
                         get_cwq(cpu, wq)->max_active = 0;
 
@@ -2856,11 +3009,35 @@ EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
  */
 void destroy_workqueue(struct workqueue_struct *wq)
 {
+        unsigned int flush_cnt = 0;
         unsigned int cpu;
 
+        /*
+         * Mark @wq dying and drain all pending works.  Once WQ_DYING is
+         * set, only chain queueing is allowed.  IOW, only currently
+         * pending or running work items on @wq can queue further work
+         * items on it.  @wq is flushed repeatedly until it becomes empty.
+         * The number of flushing is detemined by the depth of chaining and
+         * should be relatively short.  Whine if it takes too long.
+         */
         wq->flags |= WQ_DYING;
+reflush:
         flush_workqueue(wq);
 
+        for_each_cwq_cpu(cpu, wq) {
+                struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+                if (!cwq->nr_active && list_empty(&cwq->delayed_works))
+                        continue;
+
+                if (++flush_cnt == 10 ||
+                    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
+                        printk(KERN_WARNING "workqueue %s: flush on "
+                               "destruction isn't complete after %u tries\n",
+                               wq->name, flush_cnt);
+                goto reflush;
+        }
+
         /*
          * wq list is used to freeze wq, remove from list after
          * flushing is complete in case freeze races us.
@@ -2916,7 +3093,7 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
 
                 spin_lock_irq(&gcwq->lock);
 
-                if (!(wq->flags & WQ_FREEZEABLE) ||
+                if (!(wq->flags & WQ_FREEZABLE) ||
                     !(gcwq->flags & GCWQ_FREEZING))
                         get_cwq(gcwq->cpu, wq)->max_active = max_active;
 
@@ -3166,7 +3343,7 @@ static int __cpuinit trustee_thread(void *__gcwq)
          * 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
+         * may be frozen works in freezable cwqs.  Don't declare
          * completion while frozen.
          */
         while (gcwq->nr_workers != gcwq->nr_idle ||
@@ -3424,9 +3601,9 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
 /**
  * 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.
+ * Start freezing workqueues.  After this function returns, all freezable
+ * workqueues will queue new works to their frozen_works list instead of
+ * gcwq->worklist.
  *
  * CONTEXT:
  * Grabs and releases workqueue_lock and gcwq->lock's.
@@ -3452,7 +3629,7 @@ void freeze_workqueues_begin(void)
                 list_for_each_entry(wq, &workqueues, list) {
                         struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 
-                        if (cwq && wq->flags & WQ_FREEZEABLE)
+                        if (cwq && wq->flags & WQ_FREEZABLE)
                                 cwq->max_active = 0;
                 }
 
@@ -3463,7 +3640,7 @@ void freeze_workqueues_begin(void)
 }
 
 /**
- * freeze_workqueues_busy - are freezeable workqueues still busy?
+ * freeze_workqueues_busy - are freezable workqueues still busy?
  *
  * Check whether freezing is complete.  This function must be called
  * between freeze_workqueues_begin() and thaw_workqueues().
@@ -3472,8 +3649,8 @@ void freeze_workqueues_begin(void)
  * Grabs and releases workqueue_lock.
  *
  * RETURNS:
- * %true if some freezeable workqueues are still busy.  %false if
- * freezing is complete.
+ * %true if some freezable workqueues are still busy.  %false if freezing
+ * is complete.
  */
 bool freeze_workqueues_busy(void)
 {
@@ -3493,7 +3670,7 @@ bool freeze_workqueues_busy(void)
                 list_for_each_entry(wq, &workqueues, list) {
                         struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 
-                        if (!cwq || !(wq->flags & WQ_FREEZEABLE))
+                        if (!cwq || !(wq->flags & WQ_FREEZABLE))
                                 continue;
 
                         BUG_ON(cwq->nr_active < 0);
@@ -3538,7 +3715,7 @@ void thaw_workqueues(void)
                 list_for_each_entry(wq, &workqueues, list) {
                         struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
 
-                        if (!cwq || !(wq->flags & WQ_FREEZEABLE))
+                        if (!cwq || !(wq->flags & WQ_FREEZABLE))
                                 continue;
 
                         /* restore max_active and repopulate worklist */
@@ -3612,7 +3789,10 @@ static int __init init_workqueues(void)
         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);
+        system_freezable_wq = alloc_workqueue("events_freezable",
+                                              WQ_FREEZABLE, 0);
+        BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
+               !system_unbound_wq || !system_freezable_wq);
         return 0;
 }
 early_initcall(init_workqueues);