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Subject[PATCH 09/13] workqueue: add lock_pool_queued_work()
Date
Extract lock code from try_to_grab_pending() and name it lock_pool_queued_work().
It makes the code better readability and make try_to_grab_pending() shorter,

And this new function can be reused by other(later patch).

Add/Use proper locking API.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
kernel/workqueue.c | 100 ++++++++++++++++++++++++++++++---------------------
1 files changed, 59 insertions(+), 41 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 6e92f18..a108788 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -971,6 +971,45 @@ static struct worker_pool *lock_pool_executing_work(struct work_struct *work,
return NULL;
}

+/** lock_pool_queued_work - lock the pool a given work is queued on
+ * @work: work of interest
+ *
+ * CONTEXT:
+ * local_irq_disable()
+ *
+ * RETURNS:
+ * Pointer to work pool(and locked) on which @work is queued if found,
+ * NULL otherwise.
+ */
+static struct worker_pool *lock_pool_queued_work(struct work_struct *work)
+{
+ struct cpu_workqueue_struct *cwq = get_work_cwq(work);
+ struct worker_pool *pool;
+
+ if (!cwq)
+ return NULL;
+
+ pool = cwq->pool;
+ spin_lock(&pool->lock);
+ /*
+ * The CWQ bit is set/cleared only when we do enqueue/dequeue the work
+ * When a work is enqueued(insert_work()) to a pool:
+ * we set cwq(CWQ bit) with pool->lock held
+ * when a work is dequeued(process_one_work(),try_to_grab_pending()):
+ * we clear cwq(CWQ bit) with pool->lock held
+ *
+ * So when if the pool->lock is held, we can determine:
+ * CWQ bit is set and the cwq->pool == pool
+ * <==> the work is queued on the pool
+ */
+ cwq = get_work_cwq(work);
+ if (cwq && cwq->pool == pool)
+ return pool;
+ spin_unlock(&pool->lock);
+
+ return NULL;
+}
+
/**
* move_linked_works - move linked works to a list
* @work: start of series of works to be scheduled
@@ -1104,7 +1143,6 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
unsigned long *flags)
{
struct worker_pool *pool;
- struct cpu_workqueue_struct *cwq;

local_irq_save(*flags);

@@ -1129,49 +1167,29 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
* The queueing is in progress, or it is already queued. Try to
* steal it from ->worklist without clearing WORK_STRUCT_PENDING.
*/
- pool = get_work_pool(work);
- if (!pool)
- goto fail;
-
- spin_lock(&pool->lock);
- /*
- * The CWQ bit is set/cleared only when we do enqueue/dequeue the work
- * When a work is enqueued(insert_work()) to a pool:
- * we set cwq(CWQ bit) with pool->lock held
- * when a work is dequeued(process_one_work(),try_to_grab_pending()):
- * we clear cwq(CWQ bit) with pool->lock held
- *
- * So when if the pool->lock is held, we can determine:
- * CWQ bit is set and the cwq->pool == pool
- * <==> the work is queued on the pool
- */
- cwq = get_work_cwq(work);
- if (cwq) {
- if (pool == cwq->pool) {
- debug_work_deactivate(work);
+ pool = lock_pool_queued_work(work);
+ if (pool) {
+ debug_work_deactivate(work);

- /*
- * A delayed work item cannot be grabbed directly
- * because it might have linked NO_COLOR work items
- * which, if left on the delayed_list, will confuse
- * cwq->nr_active management later on and cause
- * stall. Make sure the work item is activated
- * before grabbing.
- */
- if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
- cwq_activate_delayed_work(work);
+ /*
+ * A delayed work item cannot be grabbed directly
+ * because it might have linked NO_COLOR work items
+ * which, if left on the delayed_list, will confuse
+ * cwq->nr_active management later on and cause
+ * stall. Make sure the work item is activated
+ * before grabbing.
+ */
+ if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
+ cwq_activate_delayed_work(work);

- list_del_init(&work->entry);
- cwq_dec_nr_in_flight(get_work_cwq(work),
- get_work_color(work));
+ list_del_init(&work->entry);
+ cwq_dec_nr_in_flight(get_work_cwq(work), get_work_color(work));

- clear_work_cwq(work, pool->id);
- spin_unlock(&pool->lock);
- return 1;
- }
+ clear_work_cwq(work, pool->id);
+ spin_unlock(&pool->lock);
+ return 1;
}
- spin_unlock(&pool->lock);
-fail:
+
local_irq_restore(*flags);
if (work_is_canceling(work))
return -ENOENT;
@@ -2821,7 +2839,7 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
return false;

spin_lock_irq(&pool->lock);
- /* See the comment near try_to_grab_pending() with the same code */
+ /* See the comment near lock_pool_queued_work() with the same code */
cwq = get_work_cwq(work);
if (cwq) {
if (unlikely(pool != cwq->pool))
--
1.7.7.6


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