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Merge branch 'for-3.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq into for-3.7

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This merge is necessary as Lai's CPU hotplug restructuring series
depends on the CPU hotplug bug fixes in for-3.6-fixes.

The merge creates one trivial conflict between the following two
commits.

 96e65306b8 "workqueue: UNBOUND -> REBIND morphing in rebind_workers() should be atomic"
 e2b6a6d570 "workqueue: use system_highpri_wq for highpri workers in rebind_workers()"

Both add local variable definitions to the same block and can be
merged in any order.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2012-09-17 16:07:34 -07:00
commit 6c1423ba5d
1 changed files with 99 additions and 23 deletions
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122
kernel/workqueue.c
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@ -66,6 +66,7 @@ enum {
/* pool flags */
POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
POOL_MANAGING_WORKERS = 1 << 1, /* managing workers */
/* worker flags */
WORKER_STARTED = 1 << 0, /* started */
@ -682,7 +683,7 @@ static bool need_to_manage_workers(struct worker_pool *pool)
/* Do we have too many workers and should some go away? */
static bool too_many_workers(struct worker_pool *pool)
{
bool managing = mutex_is_locked(&pool->manager_mutex);
bool managing = pool->flags & POOL_MANAGING_WORKERS;
int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
int nr_busy = pool->nr_workers - nr_idle;
@ -1632,6 +1633,15 @@ static void idle_worker_rebind(struct worker *worker)
/* we did our part, wait for rebind_workers() to finish up */
wait_event(gcwq->rebind_hold, !(worker->flags & WORKER_REBIND));
/*
* rebind_workers() shouldn't finish until all workers passed the
* above WORKER_REBIND wait. Tell it when done.
*/
spin_lock_irq(&worker->pool->gcwq->lock);
if (!--worker->idle_rebind->cnt)
complete(&worker->idle_rebind->done);
spin_unlock_irq(&worker->pool->gcwq->lock);
}
/*
@ -1645,8 +1655,16 @@ static void busy_worker_rebind_fn(struct work_struct *work)
struct worker *worker = container_of(work, struct worker, rebind_work);
struct global_cwq *gcwq = worker->pool->gcwq;
if (worker_maybe_bind_and_lock(worker))
worker_clr_flags(worker, WORKER_REBIND);
worker_maybe_bind_and_lock(worker);
/*
* %WORKER_REBIND must be cleared even if the above binding failed;
* otherwise, we may confuse the next CPU_UP cycle or oops / get
* stuck by calling idle_worker_rebind() prematurely. If CPU went
* down again inbetween, %WORKER_UNBOUND would be set, so clearing
* %WORKER_REBIND is always safe.
*/
worker_clr_flags(worker, WORKER_REBIND);
spin_unlock_irq(&gcwq->lock);
}
@ -1702,12 +1720,15 @@ retry:
/* set REBIND and kick idle ones, we'll wait for these later */
for_each_worker_pool(pool, gcwq) {
list_for_each_entry(worker, &pool->idle_list, entry) {
unsigned long worker_flags = worker->flags;
if (worker->flags & WORKER_REBIND)
continue;
/* morph UNBOUND to REBIND */
worker->flags &= ~WORKER_UNBOUND;
worker->flags |= WORKER_REBIND;
/* morph UNBOUND to REBIND atomically */
worker_flags &= ~WORKER_UNBOUND;
worker_flags |= WORKER_REBIND;
ACCESS_ONCE(worker->flags) = worker_flags;
idle_rebind.cnt++;
worker->idle_rebind = &idle_rebind;
@ -1725,26 +1746,16 @@ retry:
goto retry;
}
/*
* All idle workers are rebound and waiting for %WORKER_REBIND to
* be cleared inside idle_worker_rebind(). Clear and release.
* Clearing %WORKER_REBIND from this foreign context is safe
* because these workers are still guaranteed to be idle.
*/
for_each_worker_pool(pool, gcwq)
list_for_each_entry(worker, &pool->idle_list, entry)
worker->flags &= ~WORKER_REBIND;
wake_up_all(&gcwq->rebind_hold);
/* rebind busy workers */
/* all idle workers are rebound, rebind busy workers */
for_each_busy_worker(worker, i, pos, gcwq) {
unsigned long worker_flags = worker->flags;
struct work_struct *rebind_work = &worker->rebind_work;
struct workqueue_struct *wq;
/* morph UNBOUND to REBIND */
worker->flags &= ~WORKER_UNBOUND;
worker->flags |= WORKER_REBIND;
/* morph UNBOUND to REBIND atomically */
worker_flags &= ~WORKER_UNBOUND;
worker_flags |= WORKER_REBIND;
ACCESS_ONCE(worker->flags) = worker_flags;
if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
work_data_bits(rebind_work)))
@ -1765,6 +1776,34 @@ retry:
worker->scheduled.next,
work_color_to_flags(WORK_NO_COLOR));
}
/*
* All idle workers are rebound and waiting for %WORKER_REBIND to
* be cleared inside idle_worker_rebind(). Clear and release.
* Clearing %WORKER_REBIND from this foreign context is safe
* because these workers are still guaranteed to be idle.
*
* We need to make sure all idle workers passed WORKER_REBIND wait
* in idle_worker_rebind() before returning; otherwise, workers can
* get stuck at the wait if hotplug cycle repeats.
*/
idle_rebind.cnt = 1;
INIT_COMPLETION(idle_rebind.done);
for_each_worker_pool(pool, gcwq) {
list_for_each_entry(worker, &pool->idle_list, entry) {
worker->flags &= ~WORKER_REBIND;
idle_rebind.cnt++;
}
}
wake_up_all(&gcwq->rebind_hold);
if (--idle_rebind.cnt) {
spin_unlock_irq(&gcwq->lock);
wait_for_completion(&idle_rebind.done);
spin_lock_irq(&gcwq->lock);
}
}
static struct worker *alloc_worker(void)
@ -2110,9 +2149,45 @@ static bool manage_workers(struct worker *worker)
struct worker_pool *pool = worker->pool;
bool ret = false;
if (!mutex_trylock(&pool->manager_mutex))
if (pool->flags & POOL_MANAGING_WORKERS)
return ret;
pool->flags |= POOL_MANAGING_WORKERS;
/*
* To simplify both worker management and CPU hotplug, hold off
* management while hotplug is in progress. CPU hotplug path can't
* grab %POOL_MANAGING_WORKERS to achieve this because that can
* lead to idle worker depletion (all become busy thinking someone
* else is managing) which in turn can result in deadlock under
* extreme circumstances. Use @pool->manager_mutex to synchronize
* manager against CPU hotplug.
*
* manager_mutex would always be free unless CPU hotplug is in
* progress. trylock first without dropping @gcwq->lock.
*/
if (unlikely(!mutex_trylock(&pool->manager_mutex))) {
spin_unlock_irq(&pool->gcwq->lock);
mutex_lock(&pool->manager_mutex);
/*
* CPU hotplug could have happened while we were waiting
* for manager_mutex. Hotplug itself can't handle us
* because manager isn't either on idle or busy list, and
* @gcwq's state and ours could have deviated.
*
* As hotplug is now excluded via manager_mutex, we can
* simply try to bind. It will succeed or fail depending
* on @gcwq's current state. Try it and adjust
* %WORKER_UNBOUND accordingly.
*/
if (worker_maybe_bind_and_lock(worker))
worker->flags &= ~WORKER_UNBOUND;
else
worker->flags |= WORKER_UNBOUND;
ret = true;
}
pool->flags &= ~POOL_MANAGE_WORKERS;
/*
@ -2122,6 +2197,7 @@ static bool manage_workers(struct worker *worker)
ret |= maybe_destroy_workers(pool);
ret |= maybe_create_worker(pool);
pool->flags &= ~POOL_MANAGING_WORKERS;
mutex_unlock(&pool->manager_mutex);
return ret;
}