linux-kernel - [RFC PATCH 7/8] workqueue: Remove the outer loop in maybe_create

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Date:   Thu,  4 Aug 2022 16:41:34 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Lai Jiangshan <jiangshan.ljs@...group.com>,
        Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: [RFC PATCH 7/8] workqueue: Remove the outer loop in maybe_create_worker()

From: Lai Jiangshan <jiangshan.ljs@...group.com>

worker_thread() always does the recheck after getting the manager role,
so the recheck in the maybe_create_worker() is unneeded and is removed.

A piece of comment for maybe_create_worker() is removed because it is
not true anymore after the recheck is removed.

A piece of comment for manage_workers() is removed because there is
already another piece of comment explaining the same thing which is
more accurate.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 kernel/workqueue.c | 15 ---------------
 1 file changed, 15 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 64dc1833d11a..0d9844b81482 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2091,9 +2091,6 @@ static void pool_mayday_timeout(struct timer_list *t)
  * sent to all rescuers with works scheduled on @pool to resolve
  * possible allocation deadlock.
  *
- * On return, need_to_create_worker() is guaranteed to be %false and
- * may_start_working() %true.
- *
  * LOCKING:
  * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
  * multiple times.  Does GFP_KERNEL allocations.  Called only from
@@ -2103,7 +2100,6 @@ static void maybe_create_worker(struct worker_pool *pool)
 __releases(&pool->lock)
 __acquires(&pool->lock)
 {
-restart:
 	raw_spin_unlock_irq(&pool->lock);
 
 	/* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
@@ -2121,13 +2117,6 @@ __acquires(&pool->lock)
 
 	del_timer_sync(&pool->mayday_timer);
 	raw_spin_lock_irq(&pool->lock);
-	/*
-	 * This is necessary even after a new worker was just successfully
-	 * created as @pool->lock was dropped and the new worker might have
-	 * already become busy.
-	 */
-	if (need_to_create_worker(pool))
-		goto restart;
 }
 
 /**
@@ -2138,10 +2127,6 @@ __acquires(&pool->lock)
  * to.  At any given time, there can be only zero or one manager per
  * pool.  The exclusion is handled automatically by this function.
  *
- * The caller can safely start processing works on false return.  On
- * true return, it's guaranteed that need_to_create_worker() is false
- * and may_start_working() is true.
- *
  * CONTEXT:
  * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
  * multiple times.  Does GFP_KERNEL allocations.
-- 
2.19.1.6.gb485710b