From: Waiman Long <longman@redhat.com>
To: Qian Cai <cai@lca.pw>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org, Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH v2 4/4] mm/slub: Fix sysfs shrink circular locking dependency
Date: Tue, 28 Apr 2020 10:06:49 -0400 [thread overview]
Message-ID: <56327de0-fa44-d5f3-2409-69cf2b97a209@redhat.com> (raw)
In-Reply-To: <28BB8A1C-CFDF-4F5A-8686-537C3CE04818@lca.pw>
On 4/27/20 10:11 PM, Qian Cai wrote:
>
>> On Apr 27, 2020, at 9:39 PM, Waiman Long <longman@redhat.com> wrote:
>>
>> The sequence that was prevented by this patch is "kn->count --> mem_hotplug_lock.rwsem". This sequence isn't directly in the splat. Once this link is broken, the 3-lock circular loop cannot be formed. Maybe I should modify the commit log to make this point more clear.
> I don’t know what you are talking about. Once trylock succeed once, you will have kn->count —> cpu/memory_hotplug_lock.
>
Trylock is handled differently from lockdep's perspective as trylock can
failed. When trylock succeeds, the critical section is executed. As long
as it doesn't try to acquire another lock in the circular chain, the
execution will finish at some point and release the lock. On the other
hand, if another task has already held all those locks, the trylock will
fail and held locks should be released. Again, no deadlock will happen.
Regards,
Longman
next prev parent reply other threads:[~2020-04-28 14:07 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-27 23:56 [PATCH v2 0/4] mm/slub: Fix sysfs " Waiman Long
2020-04-27 23:56 ` [PATCH v2 1/4] mm, slab: Revert "extend slab/shrink to shrink all memcg caches" Waiman Long
2020-04-27 23:56 ` [PATCH v2 2/4] mm/slub: Fix slab_mutex circular locking problem in slab_attr_store() Waiman Long
2020-04-27 23:56 ` [PATCH v2 3/4] mm/slub: Fix another circular locking dependency " Waiman Long
[not found] ` <F1FA6654-C07C-42FD-B497-61EB635B264C@lca.pw>
2020-05-18 22:05 ` Waiman Long
2020-04-27 23:56 ` [PATCH v2 4/4] mm/slub: Fix sysfs shrink circular locking dependency Waiman Long
2020-04-28 0:13 ` Qian Cai
2020-04-28 1:39 ` Waiman Long
2020-04-28 2:11 ` Qian Cai
2020-04-28 14:06 ` Waiman Long [this message]
2020-04-29 2:52 ` Qian Cai
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=56327de0-fa44-d5f3-2409-69cf2b97a209@redhat.com \
--to=longman@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=cai@lca.pw \
--cc=cgroups@vger.kernel.org \
--cc=cl@linux.com \
--cc=hannes@cmpxchg.org \
--cc=iamjoonsoo.kim@lge.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=penberg@kernel.org \
--cc=rientjes@google.com \
--cc=vdavydov.dev@gmail.com \
/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