Re: [PATCH v2] ufs: core: fix ufshcd_abort_all racing issue

[Wenchao Hao <haowenchao22@gmail.com>]

On 2024/6/27 18:58, Peter Wang (王信友) wrote:
> On Thu, 2024-06-27 at 15:59 +0800, Wenchao Hao wrote:
>>
>> Hi Peter, 
>>
>> What is queue_num's offset of blk_mq_hw_ctx in your machine?
>>
>> gdb vmlinux
>>
>> (gdb) print /x (int)&((struct blk_mq_hw_ctx *)0)->queue_num
>> $5 = 0x164
>>
>> I read your descriptions and wondered a same race flow as you
>> described
>> following. But I found the offset mismatch, if the racing flow is
>> correct,
>> then the address accessed in blk_mq_unique_tag() should be 0x164, not
>> 0x194.
>> Maybe the offset is different between our machine?
>>
>> What's more, if the racing flow is correct, I did not get how your
>> changes
>> can address this racing flow.
>>
>>
> 
> Hi Wenchao Hao,
> 
> Yes, our queue_num's offset of blk_mq_hw_ctx is 0x194.
> Our kernel version is: Linux version 6.1.68
> I think the offset is different by kernel version.
> 
> (gdb) print /x (int)&((struct blk_mq_hw_ctx *)0)->queue_num
> $1 = 0x194
> 
> And yes, it only shorten the race window of step3 and step5.
> Reduce the probability of step 4 appearing between step 3 and step 5.
> 
> 

Hi Peter,

Thanks for your reply, I understand the issue now.

> Thanks.
> Peter