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Subject[PATCH 10/13] workqueue: add lock_pool_own_work() and remove get_work_pool()
Date
lock_pool_own_work() reuse lock_pool_queued_work() and lock_pool_executing_work()
to implement "get the correct own pool and lock" logic. It makes all callings
to lock_pool_own_work()'s mean/logic are more clear.

get_work_pool() can't get the really pool which owns the work
and it is not used any more, just remove it.

Add/Use proper locking API.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
kernel/workqueue.c | 123 ++++++++++++++++++++++++++--------------------------
1 files changed, 62 insertions(+), 61 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index a108788..04d1286 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -531,10 +531,8 @@ static int work_next_color(int color)
* work->data. These functions should only be called while the work is
* owned - ie. while the PENDING bit is set.
*
- * get_work_pool() and get_work_cwq() can be used to obtain the pool or cwq
- * corresponding to a work. Pool is available once the work has been
- * queued anywhere after initialization until it is sync canceled. cwq is
- * available only while the work item is queued.
+ * get_work_cwq() can be used to obtain the cwq, it is available only
+ * while the work item is queued.
*
* %WORK_OFFQ_CANCELING is used to mark a work item which is being
* canceled. While being canceled, a work item may have its PENDING set
@@ -592,31 +590,6 @@ static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
}

/**
- * get_work_pool - return the worker_pool a given work was associated with
- * @work: the work item of interest
- *
- * Return the worker_pool @work was last associated with. %NULL if none.
- */
-static struct worker_pool *get_work_pool(struct work_struct *work)
-{
- unsigned long data = atomic_long_read(&work->data);
- struct worker_pool *pool;
- int pool_id;
-
- if (data & WORK_STRUCT_CWQ)
- return ((struct cpu_workqueue_struct *)
- (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
-
- pool_id = data >> WORK_OFFQ_POOL_SHIFT;
- if (pool_id == WORK_OFFQ_POOL_NONE)
- return NULL;
-
- pool = worker_pool_by_id(pool_id);
- WARN_ON_ONCE(!pool);
- return pool;
-}
-
-/**
* offq_work_pool_id - return the worker pool ID a given work is associated with
* @work: the off-queued work item of interest
*
@@ -936,6 +909,7 @@ static struct worker *find_worker_executing_work(struct worker_pool *pool,

/** lock_pool_executing_work - lock the pool a given offq work is running on
* @work: work of interest
+ * @pool_id: pool_id obtained from @work data
* @worker: return the worker which is executing @work if found
*
* CONTEXT:
@@ -946,9 +920,9 @@ static struct worker *find_worker_executing_work(struct worker_pool *pool,
* NULL otherwise.
*/
static struct worker_pool *lock_pool_executing_work(struct work_struct *work,
+ unsigned long pool_id,
struct worker **worker)
{
- unsigned long pool_id = offq_work_pool_id(work);
struct worker_pool *pool;
struct worker *exec;

@@ -973,6 +947,7 @@ static struct worker_pool *lock_pool_executing_work(struct work_struct *work,

/** lock_pool_queued_work - lock the pool a given work is queued on
* @work: work of interest
+ * @cwq: cwq obtained from @work data
*
* CONTEXT:
* local_irq_disable()
@@ -981,14 +956,12 @@ static struct worker_pool *lock_pool_executing_work(struct work_struct *work,
* 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)
+static
+struct worker_pool *lock_pool_queued_work(struct work_struct *work,
+ struct cpu_workqueue_struct *cwq)
{
- struct cpu_workqueue_struct *cwq = get_work_cwq(work);
struct worker_pool *pool;

- if (!cwq)
- return NULL;
-
pool = cwq->pool;
spin_lock(&pool->lock);
/*
@@ -1010,6 +983,40 @@ static struct worker_pool *lock_pool_queued_work(struct work_struct *work)
return NULL;
}

+/** lock_pool_own_work - lock the pool a given work is queued/running on
+ * @work: work of interest
+ * @worker: return the worker which is executing off-queued @work if found
+ *
+ * CONTEXT:
+ * local_irq_disable()
+ *
+ * RETURNS:
+ * Pointer to work pool(and locked) on which @work is queued/running if found,
+ * - If the work is queued on the pool, lock and return the pool, with
+ * @worker untouched. The work may or may not be running on the pool.
+ * - If the work is not queued on the pool, but it is running on the pool,
+ * lock and return the pool with @worker set to the executing worker
+ * (This step will be skipped if @worker is NULL)
+ * NULL otherwise with @worker untouched
+ */
+static struct worker_pool *lock_pool_own_work(struct work_struct *work,
+ struct worker **worker)
+{
+ unsigned long data = atomic_long_read(&work->data);
+ struct cpu_workqueue_struct *cwq;
+ unsigned long pool_id;
+
+ if (data & WORK_STRUCT_CWQ) {
+ cwq = (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
+ return lock_pool_queued_work(work, cwq);
+ } else if (worker) {
+ pool_id = data >> WORK_OFFQ_POOL_SHIFT;
+ return lock_pool_executing_work(work, pool_id, worker);
+ }
+
+ return NULL;
+}
+
/**
* move_linked_works - move linked works to a list
* @work: start of series of works to be scheduled
@@ -1167,7 +1174,7 @@ 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 = lock_pool_queued_work(work);
+ pool = lock_pool_own_work(work, NULL);
if (pool) {
debug_work_deactivate(work);

@@ -1301,7 +1308,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
* to guarantee non-reentrancy.
*/
BUG_ON(get_work_cwq(work));
- pool = lock_pool_executing_work(work, &worker);
+ pool = lock_pool_own_work(work, &worker);
if (pool && worker->current_cwq->wq != wq) {
spin_unlock(&pool->lock);
pool = NULL;
@@ -2834,22 +2841,17 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
struct cpu_workqueue_struct *cwq;

might_sleep();
- pool = get_work_pool(work);
- if (!pool)
+ local_irq_disable();
+ pool = lock_pool_own_work(work, &worker);
+ if (!pool) {
+ local_irq_enable();
return false;
+ }

- spin_lock_irq(&pool->lock);
- /* See the comment near lock_pool_queued_work() with the same code */
- cwq = get_work_cwq(work);
- if (cwq) {
- if (unlikely(pool != cwq->pool))
- goto already_gone;
- } else {
- worker = find_worker_executing_work(pool, work);
- if (!worker)
- goto already_gone;
+ if (!worker)
+ cwq = get_work_cwq(work);
+ else
cwq = worker->current_cwq;
- }

insert_wq_barrier(cwq, barr, work, worker);
spin_unlock_irq(&pool->lock);
@@ -2867,9 +2869,6 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
lock_map_release(&cwq->wq->lockdep_map);

return true;
-already_gone:
- spin_unlock_irq(&pool->lock);
- return false;
}

/**
@@ -3468,19 +3467,21 @@ EXPORT_SYMBOL_GPL(workqueue_congested);
*/
unsigned int work_busy(struct work_struct *work)
{
- struct worker_pool *pool = get_work_pool(work);
unsigned long flags;
+ struct worker_pool *pool;
+ struct worker *worker = NULL;
unsigned int ret = work_pending(work) ? WORK_BUSY_PENDING : 0;

- if (!pool)
- return ret;
-
- spin_lock_irqsave(&pool->lock, flags);
+ local_irq_save(flags);

- if (find_worker_executing_work(pool, work))
- ret |= WORK_BUSY_RUNNING;
+ pool = lock_pool_own_work(work, &worker);
+ if (pool) {
+ if (worker || find_worker_executing_work(pool, work))
+ ret |= WORK_BUSY_RUNNING;
+ spin_unlock(&pool->lock);
+ }

- spin_unlock_irqrestore(&pool->lock, flags);
+ local_irq_restore(flags);

return ret;
}
--
1.7.7.6


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