From: Dmitry Vyukov <dvyukov@google.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: syzbot
<bot+e7353c7141ff7cbb718e4c888a14fa92de41ebaa@syzkaller.appspotmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dan Williams <dan.j.williams@intel.com>,
Johannes Weiner <hannes@cmpxchg.org>, Jan Kara <jack@suse.cz>,
jglisse@redhat.com, LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, shli@fb.com, syzkaller-bugs@googlegroups.com,
Thomas Gleixner <tglx@linutronix.de>,
Vlastimil Babka <vbabka@suse.cz>,
ying.huang@intel.com
Subject: Re: possible deadlock in lru_add_drain_all
Date: Fri, 27 Oct 2017 11:44:58 +0200 [thread overview]
Message-ID: <CACT4Y+Y=NCy20_k4YcrCF2Q0f16UPDZBVAF=RkkZ0uSxZq5XaA@mail.gmail.com> (raw)
In-Reply-To: <20171027093418.om5e566srz2ztsrk@dhcp22.suse.cz>
On Fri, Oct 27, 2017 at 11:34 AM, Michal Hocko <mhocko@kernel.org> wrote:
> On Fri 27-10-17 02:22:40, syzbot wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> a31cc455c512f3f1dd5f79cac8e29a7c8a617af8
>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>
> I do not see such a commit. My linux-next top is next-20171018
>
> [...]
>> Chain exists of:
>> cpu_hotplug_lock.rw_sem --> &pipe->mutex/1 --> &sb->s_type->i_mutex_key#9
>>
>> Possible unsafe locking scenario:
>>
>> CPU0 CPU1
>> ---- ----
>> lock(&sb->s_type->i_mutex_key#9);
>> lock(&pipe->mutex/1);
>> lock(&sb->s_type->i_mutex_key#9);
>> lock(cpu_hotplug_lock.rw_sem);
>
> I am quite confused about this report. Where exactly is the deadlock?
> I do not see where we would get pipe mutex from inside of the hotplug
> lock. Is it possible this is just a false possitive due to cross release
> feature?
As far as I understand this CPU0/CPU1 scheme works only for simple
cases with 2 mutexes. This seem to have larger cycle as denoted by
"the existing dependency chain (in reverse order) is:" section.
next prev parent reply other threads:[~2017-10-27 9:45 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <089e0825eec8955c1f055c83d476@google.com>
2017-10-27 9:34 ` possible deadlock in lru_add_drain_all Michal Hocko
2017-10-27 9:44 ` Dmitry Vyukov [this message]
2017-10-27 9:47 ` Dmitry Vyukov
2017-10-27 13:42 ` Michal Hocko
2017-10-30 8:22 ` Michal Hocko
2017-10-30 10:09 ` Byungchul Park
2017-10-30 15:10 ` Peter Zijlstra
2017-10-30 15:22 ` Peter Zijlstra
2017-10-31 13:13 ` Michal Hocko
2017-10-31 13:51 ` Peter Zijlstra
2017-10-31 13:55 ` Dmitry Vyukov
2017-10-31 14:52 ` Peter Zijlstra
2017-10-31 14:58 ` Michal Hocko
2017-10-31 15:10 ` Peter Zijlstra
2017-11-01 8:59 ` Byungchul Park
2017-11-01 12:01 ` Peter Zijlstra
2017-11-01 23:54 ` Byungchul Park
2018-02-14 14:01 ` Dmitry Vyukov
2018-02-14 15:44 ` Michal Hocko
2018-02-14 15:57 ` Dmitry Vyukov
2017-10-31 15:25 ` Peter Zijlstra
2017-10-31 15:45 ` Michal Hocko
2017-10-31 16:30 ` Peter Zijlstra
2017-11-01 8:31 ` Byungchul Park
2017-10-30 10:26 ` Byungchul Park
2017-10-30 11:48 ` Michal Hocko
2017-10-27 11:27 ` Vlastimil Babka
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