From: Bart Van Assche <bvanassche@acm.org>
To: Johannes Berg <johannes@sipsolutions.net>, 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 3/3] kernel/workqueue: Suppress a false positive lockdep complaint
Date: Thu, 25 Oct 2018 10:11:51 -0700 [thread overview]
Message-ID: <1540487511.66186.31.camel@acm.org> (raw)
In-Reply-To: <2cebeb88640433ce473bc40f9a5c7e06d0661e4d.camel@sipsolutions.net>
On Thu, 2018-10-25 at 19:02 +0200, Johannes Berg wrote:
> On Thu, 2018-10-25 at 15:05 +0000, Bart Van Assche wrote:
> > It can happen that the direct I/O queue creates and destroys an empty
> > workqueue from inside a work function.
>
> So, thinking about this more, can you guarantee (somehow) that the
> workqueue is empty at this point?
In general, no. But for the direct I/O case this can be guaranteed. Please
have a look at the code in sb_init_dio_done_wq() if you would not yet have
done this.
> Do you know how to reproduce this?
The lockdep complaint in the patch description is easy to reproduce. The
way I reproduce it is as follows:
git clone https://github.com/osandov/blktests
(cd blktests && ./check -q nvmeof-mp)
Bart.
next prev parent reply other threads:[~2018-10-25 17:11 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
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 [this message]
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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