linux-kernel - [RFC PATCH 6/8] workqueue: Simplify the starting of the newly created worker

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Message-Id: <20220804084135.92425-7-jiangshanlai@gmail.com>
Date:   Thu,  4 Aug 2022 16:41:33 +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 6/8] workqueue: Simplify the starting of the newly created worker

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

There is no point for the newly created worker entering and leaving
idle in the same pool->lock held region and checking WORKER_DIE
because it has not added to idle_list before the lock.

Avoid the code in the starting of the newly created worker and move
those code to the end of the worker_thread().

Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 kernel/workqueue.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index afe62649fb3a..64dc1833d11a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2383,31 +2383,16 @@ static int worker_thread(void *__worker)
 
 	raw_spin_lock_irq(&pool->lock);
 	worker->pool->nr_workers++;
-	worker_enter_idle(worker);
 	complete(&pool->created);
-woke_up:
-
-	/* am I supposed to die? */
-	if (unlikely(worker->flags & WORKER_DIE)) {
-		raw_spin_unlock_irq(&pool->lock);
-		WARN_ON_ONCE(!list_empty(&worker->entry));
-
-		set_task_comm(worker->task, "kworker/dying");
-		ida_free(&pool->worker_ida, worker->id);
-		worker_detach_from_pool(worker);
-		kfree(worker);
-		return 0;
-	}
 
-	worker_leave_idle(worker);
-recheck:
+loop:
 	/* no more worker necessary? */
 	if (!need_more_worker(pool))
 		goto sleep;
 
 	/* do we need to manage? */
 	if (unlikely(!may_start_working(pool)) && manage_workers(worker))
-		goto recheck;
+		goto loop;
 
 	/*
 	 * ->scheduled list can only be filled while a worker is
@@ -2457,7 +2442,21 @@ static int worker_thread(void *__worker)
 	raw_spin_unlock_irq(&pool->lock);
 	schedule();
 	raw_spin_lock_irq(&pool->lock);
-	goto woke_up;
+
+	/* am I supposed to die? */
+	if (unlikely(worker->flags & WORKER_DIE)) {
+		raw_spin_unlock_irq(&pool->lock);
+		WARN_ON_ONCE(!list_empty(&worker->entry));
+
+		set_task_comm(worker->task, "kworker/dying");
+		ida_free(&pool->worker_ida, worker->id);
+		worker_detach_from_pool(worker);
+		kfree(worker);
+		return 0;
+	}
+
+	worker_leave_idle(worker);
+	goto loop;
 }
 
 /**
-- 
2.19.1.6.gb485710b