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Message-Id: <20211223123140.3789-3-jiangshanlai@gmail.com>
Date: Thu, 23 Dec 2021 20:31:38 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>
Cc: Lai Jiangshan <laijs@...ux.alibaba.com>,
Lai Jiangshan <jiangshanlai@...il.com>
Subject: [PATCH 2/4] workqueue: Change the comments of the synchronization about the idle_list
From: Lai Jiangshan <laijs@...ux.alibaba.com>
The access to idle_list in wq_worker_sleeping() is changed to be
protected by pool->lock, so the comments above idle_list can be changed
to "L:" which is the meaning of "access with pool->lock held".
And the outdated comments in wq_worker_sleeping() is removed since
the function is not called with rq lock held any more, idle_list is
dereferenced with pool lock now.
Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
kernel/workqueue.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 29b070106f34..b3207722671c 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -162,7 +162,7 @@ struct worker_pool {
int nr_workers; /* L: total number of workers */
int nr_idle; /* L: currently idle workers */
- struct list_head idle_list; /* X: list of idle workers */
+ struct list_head idle_list; /* L: list of idle workers */
struct timer_list idle_timer; /* L: worker idle timeout */
struct timer_list mayday_timer; /* L: SOS timer for workers */
@@ -826,7 +826,7 @@ static bool too_many_workers(struct worker_pool *pool)
* Wake up functions.
*/
-/* Return the first idle worker. Safe with preemption disabled */
+/* Return the first idle worker. Called with pool->lock held. */
static struct worker *first_idle_worker(struct worker_pool *pool)
{
if (unlikely(list_empty(&pool->idle_list)))
@@ -917,13 +917,6 @@ void wq_worker_sleeping(struct task_struct *task)
return;
}
- /*
- * NOT_RUNNING is clear. This means that we're bound to and
- * running on the local cpu w/ rq lock held and preemption
- * disabled, which in turn means that none else could be
- * manipulating idle_list, so dereferencing idle_list without pool
- * lock is safe.
- */
if (atomic_dec_and_test(&pool->nr_running) &&
!list_empty(&pool->worklist)) {
next = first_idle_worker(pool);
--
2.19.1.6.gb485710b
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