From: Qian Cai <cai@lca.pw>
To: Waiman Long <longman@redhat.com>
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: Sat, 16 May 2020 21:57:58 -0400 [thread overview]
Message-ID: <3D1CF487-DD7E-4C5F-B977-D161CCED5234@lca.pw> (raw)
In-Reply-To: <20200427235621.7823-5-longman@redhat.com>
> On Apr 27, 2020, at 7:56 PM, Waiman Long <longman@redhat.com> wrote:
>
> A lockdep splat is observed by echoing "1" to the shrink sysfs file
> and then shutting down the system:
>
> [ 167.473392] Chain exists of:
> [ 167.473392] kn->count#279 --> mem_hotplug_lock.rw_sem --> slab_mutex
> [ 167.473392]
> [ 167.484323] Possible unsafe locking scenario:
> [ 167.484323]
> [ 167.490273] CPU0 CPU1
> [ 167.494825] ---- ----
> [ 167.499376] lock(slab_mutex);
> [ 167.502530] lock(mem_hotplug_lock.rw_sem);
> [ 167.509356] lock(slab_mutex);
> [ 167.515044] lock(kn->count#279);
> [ 167.518462]
> [ 167.518462] *** DEADLOCK ***
>
> It is because of the get_online_cpus() and get_online_mems() calls in
> kmem_cache_shrink() invoked via the shrink sysfs file. To fix that, we
> have to use trylock to get the memory and cpu hotplug read locks. Since
> hotplug events are rare, it should be fine to refuse a kmem caches
> shrink operation when some hotplug events are in progress.
>
> Signed-off-by: Waiman Long <longman@redhat.com>
Feel free to use,
Reviewed-by: Qian Cai <cai@lca.pw>
next prev parent reply other threads:[~2020-05-17 1:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-27 23:56 [PATCH v2 0/4] mm/slub: Fix sysfs circular locking dependency 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
2020-05-17 2:19 ` Qian Cai
2020-05-18 22:05 ` Waiman Long
2020-05-19 2:37 ` Qian Cai
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
2020-04-29 2:52 ` Qian Cai
2020-05-17 1:46 ` Qian Cai
2020-05-17 1:57 ` Qian Cai [this message]
2020-05-17 1:54 ` [PATCH v2 0/4] mm/slub: Fix sysfs " Qian Cai
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