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SubjectRe: [PATCH] sched/kthread: Complain loudly when others violate our flags
From
Date
On Thu, 2011-09-29 at 21:14 -0700, Tejun Heo wrote:
> It's rather complicated due to the way workqueues have been used. You
> can't tell whether a work really needs to be pinned to one cpu for
> correctness until actual cpu hotplug time as wq users are expected to
> flush such work items from hotplug notifiers, so wq workers should be
> pinned on the respective cpus while the cpus are up but also need to
> step aside once unplug notifiers are finished.

That really is crack, and I've always said so.

How about we fix that utter workqueue unplug nightmare..

---
Subject: workqueue: Fix cpuhotplug trainwreck

The current workqueue code does crazy stuff on cpu unplug, it relies on
forced affine breakage, thereby violating per-cpu expectations. Worse,
it tries to re-attach to a cpu if the thing comes up again before all
previously queued works are finished. This breaks (admittedly bonkers)
cpu-hotplug use that relies on a down-up cycle to push all usage away.

Introduce a new WQ_NON_AFFINE flag that indicates a per-cpu workqueue
will not respect cpu affinity and use this to migrate all its pending
works to whatever cpu is doing cpu-down.

For the rest, simply flush all per-cpu works and don't mess about.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/cpu.h | 14 +-
include/linux/workqueue.h | 5 +-
kernel/workqueue.c | 539 ++++++++++++---------------------------------
3 files changed, 152 insertions(+), 406 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index b1a635a..c9d6885 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -60,14 +60,16 @@ enum {
*/
CPU_PRI_SCHED_ACTIVE = INT_MAX,
CPU_PRI_CPUSET_ACTIVE = INT_MAX - 1,
- CPU_PRI_SCHED_INACTIVE = INT_MIN + 1,
- CPU_PRI_CPUSET_INACTIVE = INT_MIN,

/* migration should happen before other stuff but after perf */
- CPU_PRI_PERF = 20,
- CPU_PRI_MIGRATION = 10,
- /* prepare workqueues for other notifiers */
- CPU_PRI_WORKQUEUE = 5,
+ CPU_PRI_PERF = 20,
+ CPU_PRI_MIGRATION = 10,
+ CPU_PRI_WORKQUEUE_ACTIVE = 5, /* prepare workqueues for others */
+ CPU_PRI_NORMAL = 0,
+ CPU_PRI_WORKQUEUE_INACTIVE = -5, /* flush workqueues after others */
+
+ CPU_PRI_SCHED_INACTIVE = INT_MIN + 1,
+ CPU_PRI_CPUSET_INACTIVE = INT_MIN,
};

#define CPU_ONLINE 0x0002 /* CPU (unsigned)v is up */
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 0d556de..d68ead8 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -254,9 +254,10 @@ enum {
WQ_MEM_RECLAIM = 1 << 3, /* may be used for memory reclaim */
WQ_HIGHPRI = 1 << 4, /* high priority */
WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */
+ WQ_NON_AFFINE = 1 << 6, /* free to move works around cpus */

- WQ_DRAINING = 1 << 6, /* internal: workqueue is draining */
- WQ_RESCUER = 1 << 7, /* internal: workqueue has rescuer */
+ WQ_DRAINING = 1 << 7, /* internal: workqueue is draining */
+ WQ_RESCUER = 1 << 8, /* internal: workqueue has rescuer */

WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 1783aab..b067aa9 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -41,6 +41,7 @@
#include <linux/debug_locks.h>
#include <linux/lockdep.h>
#include <linux/idr.h>
+#include <linux/delay.h>

#include "workqueue_sched.h"

@@ -57,20 +58,10 @@ enum {
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_CPU_INTENSIVE = 1 << 4, /* cpu intensive */
+ WORKER_UNBOUND = 1 << 5, /* 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 */
+ WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE | WORKER_UNBOUND,

BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
@@ -84,7 +75,6 @@ enum {
(min two ticks) */
MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
CREATE_COOLDOWN = HZ, /* time to breath after fail */
- TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */

/*
* Rescue workers are used only on emergencies and shared by
@@ -136,7 +126,6 @@ struct worker {
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 */
};

/*
@@ -163,10 +152,8 @@ struct global_cwq {

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 */
+ wait_queue_head_t idle_wait;
} ____cacheline_aligned_in_smp;

/*
@@ -979,13 +966,38 @@ static bool is_chained_work(struct workqueue_struct *wq)
return false;
}

-static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
- struct work_struct *work)
+static void ___queue_work(struct workqueue_struct *wq, struct global_cwq *gcwq,
+ struct work_struct *work)
{
- struct global_cwq *gcwq;
struct cpu_workqueue_struct *cwq;
struct list_head *worklist;
unsigned int work_flags;
+
+ /* gcwq determined, get cwq and queue */
+ cwq = get_cwq(gcwq->cpu, wq);
+ trace_workqueue_queue_work(gcwq->cpu, cwq, work);
+
+ BUG_ON(!list_empty(&work->entry));
+
+ cwq->nr_in_flight[cwq->work_color]++;
+ 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 {
+ work_flags |= WORK_STRUCT_DELAYED;
+ worklist = &cwq->delayed_works;
+ }
+
+ insert_work(cwq, work, worklist, work_flags);
+}
+
+static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
+ struct work_struct *work)
+{
+ struct global_cwq *gcwq;
unsigned long flags;

debug_work_activate(work);
@@ -1031,27 +1043,32 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
spin_lock_irqsave(&gcwq->lock, flags);
}

- /* gcwq determined, get cwq and queue */
- cwq = get_cwq(gcwq->cpu, wq);
- trace_workqueue_queue_work(cpu, cwq, work);
+ ___queue_work(wq, gcwq, work);

- BUG_ON(!list_empty(&work->entry));
+ spin_unlock_irqrestore(&gcwq->lock, flags);
+}

- cwq->nr_in_flight[cwq->work_color]++;
- work_flags = work_color_to_flags(cwq->work_color);
+/**
+ * queue_work_on - queue work on specific cpu
+ * @cpu: CPU number to execute work on
+ * @wq: workqueue to use
+ * @work: work to queue
+ *
+ * Returns 0 if @work was already on a queue, non-zero otherwise.
+ *
+ * We queue the work to a specific CPU, the caller must ensure it
+ * can't go away.
+ */
+static int
+__queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
+{
+ int ret = 0;

- if (likely(cwq->nr_active < cwq->max_active)) {
- trace_workqueue_activate_work(work);
- cwq->nr_active++;
- worklist = gcwq_determine_ins_pos(gcwq, cwq);
- } else {
- work_flags |= WORK_STRUCT_DELAYED;
- worklist = &cwq->delayed_works;
+ if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
+ __queue_work(cpu, wq, work);
+ ret = 1;
}
-
- insert_work(cwq, work, worklist, work_flags);
-
- spin_unlock_irqrestore(&gcwq->lock, flags);
+ return ret;
}

/**
@@ -1068,34 +1085,19 @@ int queue_work(struct workqueue_struct *wq, struct work_struct *work)
{
int ret;

- ret = queue_work_on(get_cpu(), wq, work);
+ ret = __queue_work_on(get_cpu(), wq, work);
put_cpu();

return ret;
}
EXPORT_SYMBOL_GPL(queue_work);

-/**
- * queue_work_on - queue work on specific cpu
- * @cpu: CPU number to execute work on
- * @wq: workqueue to use
- * @work: work to queue
- *
- * Returns 0 if @work was already on a queue, non-zero otherwise.
- *
- * We queue the work to a specific CPU, the caller must ensure it
- * can't go away.
- */
int
queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
{
- int ret = 0;
+ WARN_ON(wq->flags & WQ_NON_AFFINE);

- if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
- __queue_work(cpu, wq, work);
- ret = 1;
- }
- return ret;
+ return __queue_work_on(cpu, wq, work);
}
EXPORT_SYMBOL_GPL(queue_work_on);

@@ -1141,6 +1143,8 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct timer_list *timer = &dwork->timer;
struct work_struct *work = &dwork->work;

+ WARN_ON((wq->flags & WQ_NON_AFFINE) && cpu != -1);
+
if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
unsigned int lcpu;

@@ -1206,12 +1210,13 @@ static void worker_enter_idle(struct worker *worker)
/* 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);
+ if (gcwq->nr_idle == gcwq->nr_workers)
+ wake_up_all(&gcwq->idle_wait);
+
+ if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer)) {
+ mod_timer(&gcwq->idle_timer,
+ jiffies + IDLE_WORKER_TIMEOUT);
+ }

/* sanity check nr_running */
WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
@@ -1303,23 +1308,6 @@ __acquires(&gcwq->lock)
}
}

-/*
- * 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;
@@ -1328,7 +1316,6 @@ static struct worker *alloc_worker(void)
if (worker) {
INIT_LIST_HEAD(&worker->entry);
INIT_LIST_HEAD(&worker->scheduled);
- INIT_WORK(&worker->rebind_work, worker_rebind_fn);
/* on creation a worker is in !idle && prep state */
worker->flags = WORKER_PREP;
}
@@ -1668,13 +1655,6 @@ static bool manage_workers(struct worker *worker)

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;
}

@@ -3214,171 +3194,71 @@ EXPORT_SYMBOL_GPL(work_busy);
* gcwqs serve mix of short, long and very long running works making
* blocked draining impractical.
*
- * This is solved by allowing a gcwq to be detached from CPU, running
- * it with unbound (rogue) workers and allowing it to be reattached
- * later if the cpu comes back online. A separate thread is created
- * to govern a gcwq in such state and is called the trustee of the
- * gcwq.
- *
- * Trustee states and their descriptions.
- *
- * START Command state used on startup. On CPU_DOWN_PREPARE, a
- * new trustee is started with this state.
- *
- * IN_CHARGE Once started, trustee will enter this state after
- * assuming the manager role and making all existing
- * workers rogue. DOWN_PREPARE waits for trustee to
- * enter this state. After reaching IN_CHARGE, trustee
- * tries to execute the pending worklist until it's empty
- * and the state is set to BUTCHER, or the state is set
- * to RELEASE.
- *
- * BUTCHER Command state which is set by the cpu callback after
- * the cpu has went down. Once this state is set trustee
- * knows that there will be no new works on the worklist
- * and once the worklist is empty it can proceed to
- * killing idle workers.
- *
- * RELEASE Command state which is set by the cpu callback if the
- * cpu down has been canceled or it has come online
- * again. After recognizing this state, trustee stops
- * trying to drain or butcher and clears ROGUE, rebinds
- * all remaining workers back to the cpu and releases
- * manager role.
- *
- * DONE Trustee will enter this state after BUTCHER or RELEASE
- * is complete.
- *
- * trustee CPU draining
- * took over down complete
- * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
- * | | ^
- * | CPU is back online v return workers |
- * ----------------> RELEASE --------------
*/

-/**
- * 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); \
-})
+static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ unsigned int cpu = (unsigned long)hcpu;
+ struct global_cwq *gcwq = get_gcwq(cpu);
+ struct worker *uninitialized_var(new_worker);
+ unsigned long flags;

-/**
- * 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; \
-})
+ action &= ~CPU_TASKS_FROZEN;

-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;
+ switch (action) {
+ case CPU_UP_PREPARE:
+ BUG_ON(gcwq->first_idle);
+ new_worker = create_worker(gcwq, false);
+ if (!new_worker)
+ return NOTIFY_BAD;
+ }

- BUG_ON(gcwq->cpu != smp_processor_id());
+ /* some are called w/ irq disabled, don't disturb irq status */
+ spin_lock_irqsave(&gcwq->lock, flags);

- 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);
+ switch (action) {
+ case CPU_UP_PREPARE:
+ BUG_ON(gcwq->first_idle);
+ gcwq->first_idle = new_worker;
+ break;

- gcwq->flags |= GCWQ_MANAGING_WORKERS;
+ case CPU_UP_CANCELED:
+ destroy_worker(gcwq->first_idle);
+ gcwq->first_idle = NULL;
+ break;

- list_for_each_entry(worker, &gcwq->idle_list, entry)
- worker->flags |= WORKER_ROGUE;
+ case CPU_ONLINE:
+ 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;
+ }

- for_each_busy_worker(worker, i, pos, gcwq)
- worker->flags |= WORKER_ROGUE;
+ spin_unlock_irqrestore(&gcwq->lock, flags);

- /*
- * 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);
+ return notifier_from_errno(0);
+}

- /*
- * Sched callbacks are disabled now. Zap nr_running. After
- * this, nr_running stays zero and need_more_worker() and
- * keep_working() are always true as long as the worklist is
- * not empty.
- */
- atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
+static void flush_gcwq(struct global_cwq *gcwq)
+{
+ struct work_struct *work, *nw;
+ struct worker *worker, *n;
+ LIST_HEAD(non_affine_works);

- spin_unlock_irq(&gcwq->lock);
- del_timer_sync(&gcwq->idle_timer);
spin_lock_irq(&gcwq->lock);
+ list_for_each_entry_safe(work, nw, &gcwq->worklist, entry) {
+ struct workqueue_struct *wq = get_work_cwq(work)->wq;

- /*
- * 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);
+ if (wq->flags & WQ_NON_AFFINE)
+ list_move(&work->entry, &non_affine_works);
+ }

- /*
- * The original cpu is in the process of dying and may go away
- * anytime now. When that happens, we and all workers would
- * be migrated to other cpus. Try draining any left work. We
- * want to get it over with ASAP - spam rescuers, wake up as
- * many idlers as necessary and create new ones till the
- * worklist is empty. Note that if the gcwq is frozen, there
- * may be frozen works in freezable cwqs. Don't declare
- * completion while frozen.
- */
- while (gcwq->nr_workers != gcwq->nr_idle ||
- gcwq->flags & GCWQ_FREEZING ||
- gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
+ while (!list_empty(&gcwq->worklist)) {
int nr_works = 0;

list_for_each_entry(work, &gcwq->worklist, entry) {
@@ -3392,190 +3272,54 @@ static int __cpuinit trustee_thread(void *__gcwq)
wake_up_process(worker->task);
}

+ spin_unlock_irq(&gcwq->lock);
+
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;
+ worker = create_worker(gcwq, true);
+ if (worker)
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);
+ wait_event_timeout(gcwq->idle_wait,
+ gcwq->nr_idle == gcwq->nr_workers, HZ/10);

- /*
- * 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;
+ spin_lock_irq(&gcwq->lock);
+ }

- /* 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;
+ WARN_ON(gcwq->nr_workers != gcwq->nr_idle);

- 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));
- }
+ list_for_each_entry_safe(worker, n, &gcwq->idle_list, entry)
+ destroy_worker(worker);

- /* relinquish manager role */
- gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
+ WARN_ON(gcwq->nr_workers || gcwq->nr_idle);

- /* 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)
-__releases(&gcwq->lock)
-__acquires(&gcwq->lock)
-{
- if (!(gcwq->trustee_state == state ||
- gcwq->trustee_state == TRUSTEE_DONE)) {
- spin_unlock_irq(&gcwq->lock);
- __wait_event(gcwq->trustee_wait,
- gcwq->trustee_state == state ||
- gcwq->trustee_state == TRUSTEE_DONE);
- spin_lock_irq(&gcwq->lock);
+ gcwq = get_gcwq(get_cpu());
+ spin_lock_irq(&gcwq->lock);
+ list_for_each_entry_safe(work, nw, &non_affine_works, entry) {
+ list_del_init(&work->entry);
+ ___queue_work(get_work_cwq(work)->wq, gcwq, work);
}
+ spin_unlock_irq(&gcwq->lock);
+ put_cpu();
}

-static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
+static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
struct global_cwq *gcwq = get_gcwq(cpu);
- struct task_struct *new_trustee = NULL;
- struct worker *uninitialized_var(new_worker);
- unsigned long flags;

action &= ~CPU_TASKS_FROZEN;

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:
- 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_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:
- 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;
+ flush_gcwq(gcwq);
break;
}

- spin_unlock_irqrestore(&gcwq->lock, flags);
-
return notifier_from_errno(0);
}

@@ -3772,7 +3516,8 @@ static int __init init_workqueues(void)
unsigned int cpu;
int i;

- cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
+ cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_ACTIVE);
+ hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_INACTIVE);

/* initialize gcwqs */
for_each_gcwq_cpu(cpu) {
@@ -3795,9 +3540,7 @@ static int __init init_workqueues(void)
(unsigned long)gcwq);

ida_init(&gcwq->worker_ida);
-
- gcwq->trustee_state = TRUSTEE_DONE;
- init_waitqueue_head(&gcwq->trustee_wait);
+ init_waitqueue_head(&gcwq->idle_wait);
}

/* create the initial worker */


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