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workqueue: convert worker_pool->worker_ida to idr and implement for_each_pool_worker()

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Make worker_ida an idr - worker_idr and use it to implement
for_each_pool_worker() which will be used to simplify worker rebinding
on CPU_ONLINE.

pool->worker_idr is protected by both pool->manager_mutex and
pool->lock so that it can be iterated while holding either lock.

* create_worker() allocates ID without installing worker pointer and
  installs the pointer later using idr_replace().  This is because
  worker ID is needed when creating the actual task to name it and the
  new worker shouldn't be visible to iterations before fully
  initialized.

* In destroy_worker(), ID removal is moved before kthread_stop().
  This is again to guarantee that only fully working workers are
  visible to for_each_pool_worker().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This commit is contained in:
Tejun Heo 2013-03-19 13:45:21 -07:00
parent 14a40ffccd
commit 822d8405d1
1 changed files with 51 additions and 12 deletions
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63
kernel/workqueue.c
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@ -119,6 +119,9 @@ enum {
*
* F: wq->flush_mutex protected.
*
* MG: pool->manager_mutex and pool->lock protected. Writes require both
* locks. Reads can happen under either lock.
*
* WQ: wq_mutex protected.
*
* WR: wq_mutex protected for writes. Sched-RCU protected for reads.
@ -156,7 +159,7 @@ 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 ida worker_ida; /* L: for worker IDs */
struct idr worker_idr; /* MG: worker IDs and iteration */
struct workqueue_attrs *attrs; /* I: worker attributes */
struct hlist_node hash_node; /* WQ: unbound_pool_hash node */
@ -299,6 +302,15 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
lockdep_is_held(&pwq_lock), \
"sched RCU or pwq_lock should be held")
#ifdef CONFIG_LOCKDEP
#define assert_manager_or_pool_lock(pool) \
WARN_ONCE(!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]; \
@ -324,6 +336,22 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
if (({ assert_rcu_or_wq_mutex(); false; })) { } \
else
/**
* for_each_pool_worker - iterate through all workers of a worker_pool
* @worker: iteration cursor
* @wi: integer used for iteration
* @pool: worker_pool to iterate workers of
*
* This must be called with either @pool->manager_mutex or ->lock held.
*
* 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; })) { } \
else
/**
* for_each_pwq - iterate through all pool_workqueues of the specified workqueue
* @pwq: iteration cursor
@ -1723,14 +1751,19 @@ static struct worker *create_worker(struct worker_pool *pool)
lockdep_assert_held(&pool->manager_mutex);
/*
* ID is needed to determine kthread name. Allocate ID first
* without installing the pointer.
*/
idr_preload(GFP_KERNEL);
spin_lock_irq(&pool->lock);
while (ida_get_new(&pool->worker_ida, &id)) {
spin_unlock_irq(&pool->lock);
if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL))
goto fail;
spin_lock_irq(&pool->lock);
}
id = idr_alloc(&pool->worker_idr, NULL, 0, 0, GFP_NOWAIT);
spin_unlock_irq(&pool->lock);
idr_preload_end();
if (id < 0)
goto fail;
worker = alloc_worker();
if (!worker)
@ -1768,11 +1801,17 @@ static struct worker *create_worker(struct worker_pool *pool)
if (pool->flags & POOL_DISASSOCIATED)
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);
ida_remove(&pool->worker_ida, id);
idr_remove(&pool->worker_idr, id);
spin_unlock_irq(&pool->lock);
}
kfree(worker);
@ -1832,7 +1871,6 @@ static int create_and_start_worker(struct worker_pool *pool)
static void destroy_worker(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
int id = worker->id;
lockdep_assert_held(&pool->manager_mutex);
lockdep_assert_held(&pool->lock);
@ -1850,13 +1888,14 @@ static void destroy_worker(struct worker *worker)
list_del_init(&worker->entry);
worker->flags |= WORKER_DIE;
idr_remove(&pool->worker_idr, worker->id);
spin_unlock_irq(&pool->lock);
kthread_stop(worker->task);
kfree(worker);
spin_lock_irq(&pool->lock);
ida_remove(&pool->worker_ida, id);
}
static void idle_worker_timeout(unsigned long __pool)
@ -3482,7 +3521,7 @@ static int init_worker_pool(struct worker_pool *pool)
mutex_init(&pool->manager_arb);
mutex_init(&pool->manager_mutex);
ida_init(&pool->worker_ida);
idr_init(&pool->worker_idr);
INIT_HLIST_NODE(&pool->hash_node);
pool->refcnt = 1;
@ -3498,7 +3537,7 @@ static void rcu_free_pool(struct rcu_head *rcu)
{
struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
ida_destroy(&pool->worker_ida);
idr_destroy(&pool->worker_idr);
free_workqueue_attrs(pool->attrs);
kfree(pool);
}