From: Dmitry Vyukov <dvyukov@google.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: Jan Kara <jack@suse.cz>,
syzbot
<bot+045a1f65bdea780940bf0f795a292f4cd0b773d1@syzkaller.appspotmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
jlayton@redhat.com, LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Mel Gorman <mgorman@techsingularity.net>,
npiggin@gmail.com, rgoldwyn@suse.com,
syzkaller-bugs@googlegroups.com,
Peter Zijlstra <peterz@infradead.org>,
kernel-team@lge.com
Subject: Re: possible deadlock in generic_file_write_iter (2)
Date: Tue, 5 Dec 2017 10:19:07 +0100 [thread overview]
Message-ID: <CACT4Y+arqmp6RW4mt3EyaPqxqxPyY31kjDLftnof5DkwfyoyRQ@mail.gmail.com> (raw)
In-Reply-To: <80ba65b6-d0c2-2d3a-779b-a134af8a9054@lge.com>
On Tue, Dec 5, 2017 at 5:58 AM, Byungchul Park <byungchul.park@lge.com> wrote:
> On 12/4/2017 5:33 PM, Jan Kara wrote:
>>
>> Hello,
>>
>> adding Peter and Byungchul to CC since the lockdep report just looks
>> strange and cross-release seems to be involved. Guys, how did #5 get into
>> the lock chain and what does put_ucounts() have to do with sb_writers
>> there? Thanks!
>
>
> Hello Jan,
>
> In order to get full stack of #5, we have to pass a boot param,
> "crossrelease_fullstack", to the kernel. Now that it only informs
> put_ucounts() in the call trace, it's hard to find out what exactly
> happened at that time, but I can tell #5 shows:
>
> When acquire(sb_writers) in put_ucounts(), it was on the way to
> complete((completion)&req.done) of wait_for_completion() in
> devtmpfs_create_node().
>
> If acquire(sb_writers) in put_ucounts() is stuck, then
> wait_for_completion() in devtmpfs_create_node() would be also
> stuck, since complete() being in the context of acquire(sb_writers)
> cannot be called.
>
> This is why cross-release added the lock chain.
Hi,
What is cross-release? Is it something new? Should we always enable
crossrelease_fullstack during testing?
Thanks
next prev parent reply other threads:[~2017-12-05 9:19 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <94eb2c0d010a4e7897055f70535b@google.com>
2017-12-04 8:33 ` possible deadlock in generic_file_write_iter (2) Jan Kara
2017-12-05 4:58 ` Byungchul Park
2017-12-05 9:19 ` Dmitry Vyukov [this message]
2017-12-06 5:05 ` Byungchul Park
2017-12-07 0:32 ` Andrew Morton
2017-12-07 17:07 ` Dmitry Vyukov
2017-12-07 23:27 ` Byungchul Park
2017-12-05 9:41 ` Jan Kara
2017-12-06 5:34 ` Byungchul Park
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