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workqueue: Make worker_attach/detach_pool() update worker->pool

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For historical reasons, the worker attach/detach functions don't
currently manage worker->pool and the callers are manually and
inconsistently updating it.

This patch moves worker->pool updates into the worker attach/detach
functions.  This makes worker->pool consistent and clearly defines how
worker->pool updates are synchronized.

This will help later workqueue visibility improvements by allowing
safe access to workqueue information from worker->task.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2018-05-18 08:47:13 -07:00
parent 1258fae73c
commit a2d812a27a
2 changed files with 9 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

16
kernel/workqueue.c
View file

@ -1741,6 +1741,7 @@ static void worker_attach_to_pool(struct worker *worker,
worker->flags |= WORKER_UNBOUND; worker->flags |= WORKER_UNBOUND;
list_add_tail(&worker->node, &pool->workers); list_add_tail(&worker->node, &pool->workers);
worker->pool = pool;
mutex_unlock(&wq_pool_attach_mutex); mutex_unlock(&wq_pool_attach_mutex);
} }
@ -1748,19 +1749,21 @@ static void worker_attach_to_pool(struct worker *worker,
/** /**
* worker_detach_from_pool() - detach a worker from its pool * worker_detach_from_pool() - detach a worker from its pool
* @worker: worker which is attached to its pool * @worker: worker which is attached to its pool
* @pool: the pool @worker is attached to
* *
* Undo the attaching which had been done in worker_attach_to_pool(). The * Undo the attaching which had been done in worker_attach_to_pool(). The
* caller worker shouldn't access to the pool after detached except it has * caller worker shouldn't access to the pool after detached except it has
* other reference to the pool. * other reference to the pool.
*/ */
static void worker_detach_from_pool(struct worker *worker, static void worker_detach_from_pool(struct worker *worker)
struct worker_pool *pool)
{ {
struct worker_pool *pool = worker->pool;
struct completion *detach_completion = NULL; struct completion *detach_completion = NULL;
mutex_lock(&wq_pool_attach_mutex); mutex_lock(&wq_pool_attach_mutex);
list_del(&worker->node); list_del(&worker->node);
worker->pool = NULL;
if (list_empty(&pool->workers)) if (list_empty(&pool->workers))
detach_completion = pool->detach_completion; detach_completion = pool->detach_completion;
mutex_unlock(&wq_pool_attach_mutex); mutex_unlock(&wq_pool_attach_mutex);
@ -1799,7 +1802,6 @@ static struct worker *create_worker(struct worker_pool *pool)
if (!worker) if (!worker)
goto fail; goto fail;
worker->pool = pool;
worker->id = id; worker->id = id;
if (pool->cpu >= 0) if (pool->cpu >= 0)
@ -2236,7 +2238,7 @@ woke_up:
set_task_comm(worker->task, "kworker/dying"); set_task_comm(worker->task, "kworker/dying");
ida_simple_remove(&pool->worker_ida, worker->id); ida_simple_remove(&pool->worker_ida, worker->id);
worker_detach_from_pool(worker, pool); worker_detach_from_pool(worker);
kfree(worker); kfree(worker);
return 0; return 0;
} }
@ -2367,7 +2369,6 @@ repeat:
worker_attach_to_pool(rescuer, pool); worker_attach_to_pool(rescuer, pool);
spin_lock_irq(&pool->lock); spin_lock_irq(&pool->lock);
rescuer->pool = pool;
/* /*
* Slurp in all works issued via this workqueue and * Slurp in all works issued via this workqueue and
@ -2417,10 +2418,9 @@ repeat:
if (need_more_worker(pool)) if (need_more_worker(pool))
wake_up_worker(pool); wake_up_worker(pool);
rescuer->pool = NULL;
spin_unlock_irq(&pool->lock); spin_unlock_irq(&pool->lock);
worker_detach_from_pool(rescuer, pool); worker_detach_from_pool(rescuer);
spin_lock_irq(&wq_mayday_lock); spin_lock_irq(&wq_mayday_lock);
} }

2
kernel/workqueue_internal.h
View file

@ -37,7 +37,7 @@ struct worker {
/* 64 bytes boundary on 64bit, 32 on 32bit */ /* 64 bytes boundary on 64bit, 32 on 32bit */
struct task_struct *task; /* I: worker task */ struct task_struct *task; /* I: worker task */
struct worker_pool *pool; /* I: the associated pool */ struct worker_pool *pool; /* A: the associated pool */
/* L: for rescuers */ /* L: for rescuers */
struct list_head node; /* A: anchored at pool->workers */ struct list_head node; /* A: anchored at pool->workers */
/* A: runs through worker->node */ /* A: runs through worker->node */