From: Oleg Nesterov <oleg@redhat.com>
To: Aaron Tomlin <atomlin@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
david@fromorbit.com, bmr@redhat.com, jcastillo@redhat.com,
mguzik@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] fs: Use a seperate wq for do_sync_work() to avoid a potential deadlock
Date: Wed, 17 Sep 2014 20:22:02 +0200 [thread overview]
Message-ID: <20140917182202.GE19308@redhat.com> (raw)
In-Reply-To: <1410953942-32144-1-git-send-email-atomlin@redhat.com>
On 09/17, Aaron Tomlin wrote:
>
> Since do_sync_work() is a deferred function it can block indefinitely by
> design. At present do_sync_work() is added to the global system_wq.
> As such a deadlock is theoretically possible between sys_unmount() and
> sync_filesystems():
>
> * The current work fn on the system_wq (do_sync_work()) is blocked
> waiting to aquire a sb's s_umount for reading.
>
> * The "umount" task is the current owner of the s_umount in
> question but is waiting for do_sync_work() to continue.
> Thus we hit a deadlock situation.
>
I can't comment the patches in this area, but I am just curious...
Could you explain this deadlock in more details? I simply can't understand
what "waiting for do_sync_work()" actually means.
> This patch introduces a separate workqueue for do_sync_work() to avoid a
> the described deadlock.
The subject and the changelog do not match the patch, it doesn't add/use
another workqueue.
Oleg.
next prev parent reply other threads:[~2014-09-17 18:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-17 11:39 [RFC PATCH] fs: Use a seperate wq for do_sync_work() to avoid a potential deadlock Aaron Tomlin
2014-09-17 18:22 ` Oleg Nesterov [this message]
2014-09-17 20:46 ` Aaron Tomlin
2014-09-17 21:16 ` Dave Chinner
2014-09-19 15:44 ` Aaron Tomlin
2014-09-17 21:42 ` Oleg Nesterov
2014-09-19 9:35 ` Aaron Tomlin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140917182202.GE19308@redhat.com \
--to=oleg@redhat.com \
--cc=atomlin@redhat.com \
--cc=bmr@redhat.com \
--cc=david@fromorbit.com \
--cc=jcastillo@redhat.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mguzik@redhat.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.