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workqueue: pick cwq instead of pool in __queue_work()

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Currently, __queue_work() chooses the pool to queue a work item to and
then determines cwq from the target wq and the chosen pool.  This is a
bit backwards in that we can determine cwq first and simply use
cwq->pool.  This way, we can skip get_std_worker_pool() in queueing
path which will be a hurdle when implementing custom worker pools.

Update __queue_work() such that it chooses the target cwq and then use
cwq->pool instead of the other way around.  While at it, add missing
{} in an if statement.

This patch doesn't introduce any functional changes.

tj: The original patch had two get_cwq() calls - the first to
    determine the pool by doing get_cwq(cpu, wq)->pool and the second
    to determine the matching cwq from get_cwq(pool->cpu, wq).
    Updated the function such that it chooses cwq instead of pool and
    removed the second call.  Rewrote the description.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2013-02-07 13:14:20 -08:00 committed by Tejun Heo
parent 54d5b7d079
commit 8594fade39
1 changed files with 13 additions and 16 deletions
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29
kernel/workqueue.c
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@ -1193,8 +1193,6 @@ static bool is_chained_work(struct workqueue_struct *wq)
static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
struct work_struct *work)
{
bool highpri = wq->flags & WQ_HIGHPRI;
struct worker_pool *pool;
struct cpu_workqueue_struct *cwq;
struct list_head *worklist;
unsigned int work_flags;
@ -1215,7 +1213,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
WARN_ON_ONCE(!is_chained_work(wq)))
return;
/* determine pool to use */
/* determine the cwq to use */
if (!(wq->flags & WQ_UNBOUND)) {
struct worker_pool *last_pool;
@ -1228,37 +1226,36 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
* work needs to be queued on that cpu to guarantee
* non-reentrancy.
*/
pool = get_std_worker_pool(cpu, highpri);
cwq = get_cwq(cpu, wq);
last_pool = get_work_pool(work);
if (last_pool && last_pool != pool) {
if (last_pool && last_pool != cwq->pool) {
struct worker *worker;
spin_lock(&last_pool->lock);
worker = find_worker_executing_work(last_pool, work);
if (worker && worker->current_cwq->wq == wq)
pool = last_pool;
else {
if (worker && worker->current_cwq->wq == wq) {
cwq = get_cwq(last_pool->cpu, wq);
} else {
/* meh... not running there, queue here */
spin_unlock(&last_pool->lock);
spin_lock(&pool->lock);
spin_lock(&cwq->pool->lock);
}
} else {
spin_lock(&pool->lock);
spin_lock(&cwq->pool->lock);
}
} else {
pool = get_std_worker_pool(WORK_CPU_UNBOUND, highpri);
spin_lock(&pool->lock);
cwq = get_cwq(WORK_CPU_UNBOUND, wq);
spin_lock(&cwq->pool->lock);
}
/* pool determined, get cwq and queue */
cwq = get_cwq(pool->cpu, wq);
/* cwq determined, queue */
trace_workqueue_queue_work(req_cpu, cwq, work);
if (WARN_ON(!list_empty(&work->entry))) {
spin_unlock(&pool->lock);
spin_unlock(&cwq->pool->lock);
return;
}
@ -1276,7 +1273,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
insert_work(cwq, work, worklist, work_flags);
spin_unlock(&pool->lock);
spin_unlock(&cwq->pool->lock);
}
/**