linux-kernel - Re: [PATCH] cgroup: fix missing cpus_read_{lock,unlock}() in cgroup_transfer

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Date:   Mon, 22 May 2023 10:23:10 +0800
From:   Qi Zheng <qi.zheng@...ux.dev>
To:     Muchun Song <muchun.song@...ux.dev>, Tejun Heo <tj@...nel.org>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Zhao Gongyi <zhaogongyi@...edance.com>
Subject: Re: [PATCH] cgroup: fix missing cpus_read_{lock,unlock}() in
 cgroup_transfer_tasks()



On 2023/5/17 15:51, Muchun Song wrote:
> 
> 
>> On May 17, 2023, at 15:45, Qi Zheng <qi.zheng@...ux.dev> wrote:
>>
>> From: Qi Zheng <zhengqi.arch@...edance.com>
>>
>> The commit 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock()
>> deadlock") fixed the deadlock between cgroup_threadgroup_rwsem and
>> cpus_read_lock() by introducing cgroup_attach_{lock,unlock}() and removing
>> cpus_read_{lock,unlock}() from cpuset_attach(). But cgroup_transfer_tasks()
>> was missed and not handled, which will cause th following warning:
>>
>> WARNING: CPU: 0 PID: 589 at kernel/cpu.c:526 lockdep_assert_cpus_held+0x32/0x40
>> CPU: 0 PID: 589 Comm: kworker/1:4 Not tainted 6.4.0-rc2-next-20230517 #50
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
>> Workqueue: events cpuset_hotplug_workfn
>> RIP: 0010:lockdep_assert_cpus_held+0x32/0x40
>> <...>
>> Call Trace:
>>   <TASK>
>>   cpuset_attach+0x40/0x240
>>   cgroup_migrate_execute+0x452/0x5e0
>>   ? _raw_spin_unlock_irq+0x28/0x40
>>   cgroup_transfer_tasks+0x1f3/0x360
>>   ? find_held_lock+0x32/0x90
>>   ? cpuset_hotplug_workfn+0xc81/0xed0
>>   cpuset_hotplug_workfn+0xcb1/0xed0
>>   ? process_one_work+0x248/0x5b0
>>   process_one_work+0x2b9/0x5b0
>>   worker_thread+0x56/0x3b0
>>   ? process_one_work+0x5b0/0x5b0
>>   kthread+0xf1/0x120
>>   ? kthread_complete_and_exit+0x20/0x20
>>   ret_from_fork+0x1f/0x30
>>   </TASK>
>>
>> So just use the cgroup_attach_{lock,unlock}() helper to fix it.
>>
>> Fixes: 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock")
>> Reported-by: Zhao Gongyi <zhaogongyi@...edance.com>
>> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> 
> Acked-by: Muchun Song <songmuchun@...edance.com>

Thanks. And hi Tejun, Can this patch be applied?

> 
> Thanks.
> 

-- 
Thanks,
Qi