linux-kernel - Re: [PATCH] block: prevent deadlock in del

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Message-ID: <8f1183d0-dfee-9448-446e-2a8846987319@huaweicloud.com>
Date: Wed, 6 Aug 2025 08:58:21 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Hillf Danton <hdanton@...a.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: Ujwal Kundur <ujwal.kundur@...il.com>, axboe@...nel.dk,
 ming.lei@...hat.com, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 syzbot+2e9e529ac0b319316453@...kaller.appspotmail.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] block: prevent deadlock in del_gendisk()



在 2025/08/05 19:59, Hillf Danton 写道:
> On Mon, 4 Aug 2025 15:51:48 +0800 Yu Kuai wrote:
>> �� 2025/08/03 21:41, Ujwal Kundur д��:
>>> A potential unsafe locking scenario presents itself when
>>> mutex_lock(&disk->open_mutex) is called with reader's lock held on
>>> update_nr_hwq_lock:
>>>          CPU0                    CPU1
>>>          ----                    ----
>>> rlock(&set->update_nr_hwq_lock)
>>>                                  lock(&nbd->config_lock);
>>>                                  lock(&set->update_nr_hwq_lock);
>>> lock(&disk->open_mutex)
>>>
>> This problem is already fixed inside nbd by:
>> 8b428f42f3ed ("nbd: fix lockdep deadlock warning")
>>
> Deadlock still exists [1].
> 
This deadlock is a different problem, not what you claimed to fix in
this patch.

Thanks,
Kuai

> [1] https://lore.kernel.org/lkml/6891742c.050a0220.7f033.001a.GAE@google.com/
> .
>