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: <YDYEjmfcykR3achs@kroah.com>
Date:   Wed, 24 Feb 2021 08:47:26 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Xiaoming Ni <nixiaoming@...wei.com>
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 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