All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Paul E. McKenney" <paulmck@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Stephen Boyd <sboyd@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	syzbot <syzbot+d6c75f383e01426a40b4@syzkaller.appspotmail.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	syzkaller-bugs@googlegroups.com, Waiman Long <llong@redhat.com>,
	Al Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [syzbot] WARNING in __init_work
Date: Mon, 20 Sep 2021 05:38:59 -0700	[thread overview]
Message-ID: <20210920123859.GE880162@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <20210920122846.GA16661@lst.de>

On Mon, Sep 20, 2021 at 02:28:46PM +0200, Christoph Hellwig wrote:
> On Mon, Sep 20, 2021 at 02:03:36PM +1000, Dave Chinner wrote:
> > > >> >  bdi_remove_from_list mm/backing-dev.c:938 [inline]
> > > >> >  bdi_unregister+0x177/0x5a0 mm/backing-dev.c:946
> > > >> >  release_bdi+0xa1/0xc0 mm/backing-dev.c:968
> > > >> >  kref_put include/linux/kref.h:65 [inline]
> > > >> >  bdi_put+0x72/0xa0 mm/backing-dev.c:976
> > > >> >  bdev_free_inode+0x116/0x220 fs/block_dev.c:819
> > > >> >  i_callback+0x3f/0x70 fs/inode.c:224
> > > 
> > > The inode code uses RCU for freeing an inode object which then ends up
> > > calling bdi_put() and subsequently in synchronize_rcu_expedited().
> > 
> > Commit 889c05cc5834 ("block: ensure the bdi is freed after
> > inode_detach_wb") might be a good place to start looking here. It
> > moved the release of the bdi from ->evict context to the RCU freeing
> > of the blockdev inode...
> 
> Well, the block code already does a bdi_unregister in del_gendisk.
> So if we end up freeing the whole device bdev with a registered bdi
> something is badly going wrong.  Unfortunately the log in this report
> isn't much help on how we got there.  IIRC syzbot will eventually spew
> out a reproducer, so it might be worth to wait for that.

If it does turn out that you need to block in an RCU callback,
queue_rcu_work() can be helpful.  This schedules a workqueue from the RCU
callback, allowing the function passed to the preceding INIT_RCU_WORK()
to block.

							Thanx, Paul

  reply	other threads:[~2021-09-20 12:39 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-15 17:00 [syzbot] WARNING in __init_work syzbot
2021-09-15 17:00 ` syzbot
2021-09-15 23:14 ` Andrew Morton
2021-09-16  2:29   ` Stephen Boyd
2021-09-19 12:41     ` Thomas Gleixner
2021-09-20  4:03       ` Dave Chinner
2021-09-20 12:28         ` Christoph Hellwig
2021-09-20 12:38           ` Paul E. McKenney [this message]
2021-09-20 12:45             ` Christoph Hellwig
2021-09-20 12:54               ` Paul E. McKenney
2021-09-21 18:38       ` Stephen Boyd
2021-09-21 20:19         ` Thomas Gleixner

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=20210920123859.GE880162@paulmck-ThinkPad-P17-Gen-1 \
    --to=paulmck@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=axboe@kernel.dk \
    --cc=david@fromorbit.com \
    --cc=hch@lst.de \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=llong@redhat.com \
    --cc=sboyd@kernel.org \
    --cc=syzbot+d6c75f383e01426a40b4@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    --cc=tglx@linutronix.de \
    --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.