linux-kernel - Re: [PATCH stable-rc queue/4.9 1/1] futex: Provide distinct return value when owner is exiting

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Message-ID: <0b9d35bd-12a9-22f2-e08e-b3e8f0d268dd@huawei.com>
Date:   Wed, 24 Feb 2021 20:40:08 +0800
From:   Xiaoming Ni <nixiaoming@...wei.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
        <sashal@...nel.org>, <tglx@...utronix.de>, <wangle6@...wei.com>,
        <zhengyejian1@...wei.com>
Subject: Re: [PATCH stable-rc queue/4.9 1/1] futex: Provide distinct return
 value when owner is exiting

On 2021/2/24 15:47, Greg KH wrote:
> On Wed, Feb 24, 2021 at 09:41:01AM +0800, Xiaoming Ni wrote:
>> On 2021/2/23 21:00, Greg KH wrote:
>>> On Mon, Feb 22, 2021 at 10:11:37PM +0800, Xiaoming Ni wrote:
>>>> On 2021/2/22 20:09, Greg KH wrote:
>>>>> On Mon, Feb 22, 2021 at 06:54:06PM +0800, Xiaoming Ni wrote:
>>>>>> On 2021/2/22 18:16, Greg KH wrote:
>>>>>>> On Mon, Feb 22, 2021 at 03:03:28PM +0800, Xiaoming Ni wrote:
>>>>>>>> From: Thomas Gleixner<tglx@...utronix.de>
>>>>>>>>
>>>>>>>> commit ac31c7ff8624409ba3c4901df9237a616c187a5d upstream.
>>>>>>> This commit is already in the 4.9 tree.  If the backport was incorrect,
>>>>>>> say that here, and describe what went wrong and why this commit fixes
>>>>>>> it.
>>>>>>>
>>>>>>> Also state what commit this fixes as well, otherwise this changelog just
>>>>>>> looks like it is being applied again to the tree, which doesn't make
>>>>>>> much sense.
>>>>>>>
>>>>>>> thanks,
>>>>>>>
>>>>>>> greg k-h
>>>>>>> .
>>>>>>
>>>>>> I wrote a cover for it. but forgot to adjust the title of the cover:
>>>>>>
>>>>>> https://lore.kernel.org/lkml/20210222070328.102384-1-nixiaoming@huawei.com/
>>>>>>
>>>>>>
>>>>>> I found a dead code in the queue/4.9 branch of the stable-rc repository.
>>>>>>
>>>>>> 2021-02-03:
>>>>>> commit c27f392040e2f6 ("futex: Provide distinct return value when
>>>>>>     owner is exiting")
>>>>>> 	The function handle_exit_race does not exist. Therefore, the
>>>>>> 	change in handle_exit_race() is ignored in the patch round.
>>>>>>
>>>>>> 2021-02-22:
>>>>>> commit e55cb811e612 ("futex: Cure exit race")
>>>>>> 	Define the handle_exit_race() function,
>>>>>> 	but no branch in the function returns EBUSY.
>>>>>> 	As a result, dead code occurs in the attach_to_pi_owner():
>>>>>>
>>>>>> 		int ret = handle_exit_race(uaddr, uval, p);
>>>>>> 		...
>>>>>> 		if (ret == -EBUSY)
>>>>>> 			*exiting = p; /* dead code */
>>>>>>
>>>>>> To fix the dead code, modify the commit e55cb811e612 ("futex: Cure exit
>>>>>> race"),
>>>>>> or install a patch to incorporate the changes in handle_exit_race().
>>>>>>
>>>>>> I am unfamiliar with the processing of the stable-rc queue branch,
>>>>>> and I cannot find the patch mail of the current branch in
>>>>>> 	https://lore.kernel.org/lkml/?q=%22futex%3A+Cure+exit+race%22
>>>>>> Therefore, I re-integrated commit ac31c7ff8624 ("futex: Provide distinct
>>>>>>     return value when owner is exiting").
>>>>>>     And wrote a cover (but forgot to adjust the title of the cover):
>>>>>>
>>>>>> https://lore.kernel.org/lkml/20210222070328.102384-1-nixiaoming@huawei.com/
>>>>>
>>>>> So this is a "fixup" patch, right?
>>>>>
>>>>> Please clearly label it as such in your patch description and resend
>>>>> this as what is here I can not apply at all.
>>>>>
>>>>> thanks,
>>>>>
>>>>> greg k-h
>>>>> .
>>>>>
>>>> Thank you for your guidance.
>>>> I have updated the patch description and resent the patch based on
>>>> v4.9.258-rc1
>>>> https://lore.kernel.org/lkml/20210222125352.110124-1-nixiaoming@huawei.com/
>>>
>>> Can you please try 4.9.258 and let me know if this is still needed or
>>> not?
>>>
>>> thanks,
>>>
>>> greg k-h
>>> .
>>>
>> The dead code problem still exists in V4.9.258. No conflict occurs during my
>> patch integration. Do I need to correct the version number marked in the cc
>> table in the patch and resend the patch?
> 
> Please do.
> 
> thanks,
> 
> greg k-h
> .
> 
I have resend the patch based on v4.9.258.
link:
https://lore.kernel.org/lkml/20210224100923.51315-1-nixiaoming@huawei.com/

Thanks

Xiaoming Ni