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workqueue: use manager lock only to protect worker_idr 

worker_idr is highly bound to managers and is always/only accessed in manager
lock context. So we don't need pool->lock for it.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2014-05-20 17:46:27 +08:00 committed by Tejun Heo
parent cf416171e7
commit 9625ab1727
1 changed files with 6 additions and 28 deletions
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34
kernel/workqueue.c
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@ -124,8 +124,7 @@ enum {
* cpu or grabbing pool->lock is enough for read access. If
* POOL_DISASSOCIATED is set, it's identical to L.
*
* MG: pool->manager_mutex and pool->lock protected. Writes require both
* locks. Reads can happen under either lock.
* M: pool->manager_mutex protected.
*
* PL: wq_pool_mutex protected.
*
@ -164,7 +163,7 @@ struct worker_pool {
/* see manage_workers() for details on the two manager mutexes */
struct mutex manager_arb; /* manager arbitration */
struct mutex manager_mutex; /* manager exclusion */
struct idr worker_idr; /* MG: worker IDs and iteration */
struct idr worker_idr; /* M: worker IDs and iteration */
struct workqueue_attrs *attrs; /* I: worker attributes */
struct hlist_node hash_node; /* PL: unbound_pool_hash node */
@ -340,16 +339,6 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
lockdep_is_held(&wq->mutex), \
"sched RCU or wq->mutex should be held")
#ifdef CONFIG_LOCKDEP
#define assert_manager_or_pool_lock(pool) \
WARN_ONCE(debug_locks && \
!lockdep_is_held(&(pool)->manager_mutex) && \
!lockdep_is_held(&(pool)->lock), \
"pool->manager_mutex or ->lock should be held")
#else
#define assert_manager_or_pool_lock(pool) do { } while (0)
#endif
#define for_each_cpu_worker_pool(pool, cpu) \
for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
(pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
@ -378,14 +367,14 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
* @wi: integer used for iteration
* @pool: worker_pool to iterate workers of
*
* This must be called with either @pool->manager_mutex or ->lock held.
* This must be called with @pool->manager_mutex.
*
* The if/else clause exists only for the lockdep assertion and can be
* ignored.
*/
#define for_each_pool_worker(worker, wi, pool) \
idr_for_each_entry(&(pool)->worker_idr, (worker), (wi)) \
if (({ assert_manager_or_pool_lock((pool)); false; })) { } \
if (({ lockdep_assert_held(&pool->manager_mutex); false; })) { } \
else
/**
@ -1725,13 +1714,7 @@ static struct worker *create_worker(struct worker_pool *pool)
* ID is needed to determine kthread name. Allocate ID first
* without installing the pointer.
*/
idr_preload(GFP_KERNEL);
spin_lock_irq(&pool->lock);
id = idr_alloc(&pool->worker_idr, NULL, 0, 0, GFP_NOWAIT);
spin_unlock_irq(&pool->lock);
idr_preload_end();
id = idr_alloc(&pool->worker_idr, NULL, 0, 0, GFP_KERNEL);
if (id < 0)
goto fail;
@ -1773,18 +1756,13 @@ static struct worker *create_worker(struct worker_pool *pool)
worker->flags |= WORKER_UNBOUND;
/* successful, commit the pointer to idr */
spin_lock_irq(&pool->lock);
idr_replace(&pool->worker_idr, worker, worker->id);
spin_unlock_irq(&pool->lock);
return worker;
fail:
if (id >= 0) {
spin_lock_irq(&pool->lock);
if (id >= 0)
idr_remove(&pool->worker_idr, id);
spin_unlock_irq(&pool->lock);
}
kfree(worker);
return NULL;
}