From: Roman Penyaev <rpenyaev@suse.de>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: WARNING in ep_poll_callback
Date: Tue, 08 Jan 2019 11:05:08 +0100 [thread overview]
Message-ID: <a4eae0108088505de523b301b1db9663@suse.de> (raw)
In-Reply-To: <CACT4Y+aFQgqYuq9ws8vJk-f9uafx8B8hYKtMwUgjcrTGAL_spQ@mail.gmail.com>
On 2019-01-08 07:00, Dmitry Vyukov wrote:
> On Tue, Jan 8, 2019 at 6:59 AM syzbot
> <syzbot+aea82bf9ee6ffd9a79d9@syzkaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit: 139287cc2cc0 Add linux-next specific files for
>> 20190108
>> git tree: linux-next
>> console output:
>> https://syzkaller.appspot.com/x/log.txt?x=16f563d7400000
>> kernel config:
>> https://syzkaller.appspot.com/x/.config?x=1521b074ff5a5bdf
>> dashboard link:
>> https://syzkaller.appspot.com/bug?extid=aea82bf9ee6ffd9a79d9
>> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
>
> Looks like caused by:
>
> commit f92cacf118171208f62519d92502a8dd0341286d
> Author: Roman Penyaev
> Date: Tue Jan 8 12:15:44 2019 +1100
>
> epoll: loosen irq safety in ep_poll_callback()
Yes, that was my wrong assumption that all drivers disable irqs before
waking up a wait queue. Of course for drivers like fuse this is not
a case. Thanks for reporting.
The fix is simple: just remove wrong assert line :) The whole logic
stays correct: epoll always locks rwlock with irqs disabled and by
itself does not call from interrupt, thus it is up to driver how to
call wake_up_locked(), because if driver does not handle any interrupts
it is safe on its side to take a simple spin_lock.
Patch is sent:
https://lore.kernel.org/lkml/20190108100121.20247-1-rpenyaev@suse.de
--
Roman
next prev parent reply other threads:[~2019-01-08 10:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-08 5:59 syzbot
2019-01-08 6:00 ` Dmitry Vyukov
2019-01-08 10:05 ` Roman Penyaev [this message]
2019-01-08 6:21 ` syzbot
2019-03-11 13:14 ` syzbot
2019-03-11 13:37 ` Roman Penyaev
2019-03-11 13:45 ` Dmitry Vyukov
2019-03-11 13:53 ` Roman Penyaev
2019-03-11 16:36 ` Dmitry Vyukov
2019-03-11 16:36 ` syzbot
2019-03-11 16:37 ` Dmitry Vyukov
2019-03-11 17:22 ` Roman Penyaev
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=a4eae0108088505de523b301b1db9663@suse.de \
--to=rpenyaev@suse.de \
--cc=akpm@linux-foundation.org \
--cc=dvyukov@google.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sfr@canb.auug.org.au \
--cc=syzkaller-bugs@googlegroups.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®