linux-kernel - [PATCH 1/3] kernel/workqueue: Remove lockdep annotation from __flush

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Date:   Thu, 25 Oct 2018 08:05:38 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Tejun Heo <tj@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Johannes Berg <johannes.berg@...el.com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>, tytso@....edu,
        bvanassche@....org
Subject: [PATCH 1/3] kernel/workqueue: Remove lockdep annotation from __flush_work()

As documented in a comment in start_flush_work(), calling flush_work()
from a multi-threaded workqueue is safe if that workqueue is not
equipped with a rescuer. Avoid that flush_work() calls from inside a
work item executing on such a queue trigger a lockdep complaint. Remove
the lockdep annotation from __flush_work() because start_flush_work()
already has such an annotation.

Fixes: 87915adc3f0a ("workqueue: re-add lockdep dependencies for flushing")
Cc: Johannes Berg <johannes.berg@...el.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Sagi Grimberg <sagi@...mberg.me>
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 kernel/workqueue.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 0280deac392e..6755ef21a679 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2908,11 +2908,6 @@ static bool __flush_work(struct work_struct *work, bool from_cancel)
 	if (WARN_ON(!wq_online))
 		return false;
 
-	if (!from_cancel) {
-		lock_map_acquire(&work->lockdep_map);
-		lock_map_release(&work->lockdep_map);
-	}
-
 	if (start_flush_work(work, &barr, from_cancel)) {
 		wait_for_completion(&barr.done);
 		destroy_work_on_stack(&barr.work);
-- 
2.19.1.568.g152ad8e336-goog