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Subject[PATCH 3/6] workqueue: Make worker_attach/detach_pool() update worker->pool
Date
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>
---
kernel/workqueue.c | 16 ++++++++--------
kernel/workqueue_internal.h | 2 +-
2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 91fe0a6..2fde50f 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1741,6 +1741,7 @@ static void worker_attach_to_pool(struct worker *worker,
worker->flags |= WORKER_UNBOUND;

list_add_tail(&worker->node, &pool->workers);
+ worker->pool = pool;

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: 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
* caller worker shouldn't access to the pool after detached except it has
* other reference to the pool.
*/
-static void worker_detach_from_pool(struct worker *worker,
- struct worker_pool *pool)
+static void worker_detach_from_pool(struct worker *worker)
{
+ struct worker_pool *pool = worker->pool;
struct completion *detach_completion = NULL;

mutex_lock(&wq_pool_attach_mutex);
+
list_del(&worker->node);
+ worker->pool = NULL;
+
if (list_empty(&pool->workers))
detach_completion = pool->detach_completion;
mutex_unlock(&wq_pool_attach_mutex);
@@ -1799,7 +1802,6 @@ static struct worker *create_worker(struct worker_pool *pool)
if (!worker)
goto fail;

- worker->pool = pool;
worker->id = id;

if (pool->cpu >= 0)
@@ -2236,7 +2238,7 @@ static int worker_thread(void *__worker)

set_task_comm(worker->task, "kworker/dying");
ida_simple_remove(&pool->worker_ida, worker->id);
- worker_detach_from_pool(worker, pool);
+ worker_detach_from_pool(worker);
kfree(worker);
return 0;
}
@@ -2367,7 +2369,6 @@ static int rescuer_thread(void *__rescuer)
worker_attach_to_pool(rescuer, pool);

spin_lock_irq(&pool->lock);
- rescuer->pool = pool;

/*
* Slurp in all works issued via this workqueue and
@@ -2417,10 +2418,9 @@ static int rescuer_thread(void *__rescuer)
if (need_more_worker(pool))
wake_up_worker(pool);

- rescuer->pool = NULL;
spin_unlock_irq(&pool->lock);

- worker_detach_from_pool(rescuer, pool);
+ worker_detach_from_pool(rescuer);

spin_lock_irq(&wq_mayday_lock);
}
diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
index d390d1b..4a182e0 100644
--- a/kernel/workqueue_internal.h
+++ b/kernel/workqueue_internal.h
@@ -37,7 +37,7 @@ struct worker {
/* 64 bytes boundary on 64bit, 32 on 32bit */

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 */
struct list_head node; /* A: anchored at pool->workers */
/* A: runs through worker->node */
--
2.9.5
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