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Date:   Thu, 19 May 2022 16:26:51 -0700
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Subject: Re: [PATCH] cgroup: don't queue css_release_work if one already
 pending
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To:     Hillf Danton <hdanton@sina.com>, Tejun Heo <tj@kernel.org>
Cc:     Michal Koutny <mkoutny@suse.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org,
        syzbot+e42ae441c3b10acf9e9d@syzkaller.appspotmail.com
References: <20220412192459.227740-1-tadeusz.struk@linaro.org>
 <20220414164409.GA5404@blackbody.suse.cz> <YmHwOAdGY2Lwl+M3@slm.duckdns.org>
 <20220422100400.GA29552@blackbody.suse.cz>
 <20220519112319.2455-1-hdanton@sina.com>
From:   Tadeusz Struk <tadeusz.struk@linaro.org>
In-Reply-To: <20220519112319.2455-1-hdanton@sina.com>
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On 5/19/22 04:23, Hillf Danton wrote:
> On Wed, 18 May 2022 09:48:21 -0700 Tadeusz Struk  wrote:
>> On 4/22/22 04:05, Michal Koutny wrote:
>>> On Thu, Apr 21, 2022 at 02:00:56PM -1000, Tejun Heo<tj@kernel.org>  wrote:
>>>> If this is the case, we need to hold an extra reference to be put by the
>>>> css_killed_work_fn(), right?
> That put could trigger INIT_WORK in css_release() and warning [1]
> on init active (active state 0) object OTOH as the same
> css->destroy_work is used in both kill and release pathes.

Will this help if there would be two WQs, one for the css_release path
and one for the rcu_work?

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index adb820e98f24..a4873b33e488 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -124,6 +124,7 @@ DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
   * which may lead to deadlock.
   */
  static struct workqueue_struct *cgroup_destroy_wq;
+static struct workqueue_struct *cgroup_destroy_rcu_wq;
  
  /* generate an array of cgroup subsystem pointers */
  #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,

-- 
Thanks,
Tadeusz