From: Johannes Berg <johannes@sipsolutions.net>
To: Bart Van Assche <bvanassche@acm.org>, Tejun Heo <tj@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
"tytso@mit.edu" <tytso@mit.edu>
Subject: Re: [PATCH 1/3] kernel/workqueue: Remove lockdep annotation from __flush_work()
Date: Thu, 25 Oct 2018 17:31:27 +0200 [thread overview]
Message-ID: <986cb39001ee9eb11dd546b79de9e0b4b8463d19.camel@sipsolutions.net> (raw)
In-Reply-To: <20181025150540.259281-2-bvanassche@acm.org>
On Thu, 2018-10-25 at 15:05 +0000, Bart Van Assche wrote:
> 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.
So ... not sure I understand, do you happen to have an example (at least
conceptually) that shows the problem?
Something like
workqueue WQ, works W1, W2
W1 running on WQ -> flush_work(W2) also running on WQ?
I'm willing to believe that this is a corner case I missed with the
annotations since the rescuer things are tricky, but I don't think
removing them is the right thing to do.
> Remove
> the lockdep annotation from __flush_work() because start_flush_work()
> already has such an annotation.
This part at least isn't true, there's no annotation on the work
*struct*, only one on the work *queue*.
johannes
next prev parent reply other threads:[~2018-10-25 15:31 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-25 15:05 [PATCH 0/3] Suppress false positives triggered by workqueue lockdep annotations Bart Van Assche
2018-10-25 15:05 ` [PATCH 1/3] kernel/workqueue: Remove lockdep annotation from __flush_work() Bart Van Assche
2018-10-25 15:31 ` Johannes Berg [this message]
2018-10-25 15:57 ` Johannes Berg
2018-10-25 16:01 ` Bart Van Assche
2018-10-25 15:05 ` [PATCH 2/3] kernel/workqueue: Surround work execution with shared lock annotations Bart Van Assche
2018-10-25 16:53 ` Johannes Berg
2018-10-25 17:22 ` Bart Van Assche
2018-10-25 19:17 ` Johannes Berg
2018-10-25 15:05 ` [PATCH 3/3] kernel/workqueue: Suppress a false positive lockdep complaint Bart Van Assche
2018-10-25 15:34 ` Johannes Berg
2018-10-25 15:55 ` Bart Van Assche
2018-10-25 19:59 ` Johannes Berg
2018-10-25 20:21 ` Theodore Y. Ts'o
2018-10-25 20:26 ` Johannes Berg
2018-10-25 15:36 ` Tejun Heo
2018-10-25 15:37 ` Tejun Heo
2018-10-25 20:13 ` Johannes Berg
2018-10-25 15:40 ` Theodore Y. Ts'o
2018-10-25 17:02 ` Johannes Berg
2018-10-25 17:11 ` Bart Van Assche
2018-10-25 19:51 ` Johannes Berg
2018-10-25 20:39 ` Bart Van Assche
2018-10-25 20:47 ` Johannes Berg
2018-10-25 15:27 ` [PATCH 0/3] Suppress false positives triggered by workqueue lockdep annotations Johannes Berg
2018-10-25 15:47 ` Bart Van Assche
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