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

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Date:   Mon, 22 Feb 2021 22:11:37 +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 2021/2/22 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/

Thanks
Xiaoming Ni