workqueue: Change the comments of the synchronization about the idle_list

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And the outdated comments in wq_worker_sleeping() is removed since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@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 29b0701..b320772 100644 (file)
--- 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);