linux-kernel - Re: [PATCH] futex: fix dead code in attach_to_pi

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Date:   Thu, 25 Feb 2021 09:31:20 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Xiaoming Ni <nixiaoming@...wei.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, sashal@...nel.org, tglx@...utronix.de,
        wangle6@...wei.com, zhengyejian1@...wei.com
Subject: Re: [PATCH] futex: fix dead code in attach_to_pi_owner()

On Thu, 25 Feb 2021, Xiaoming Ni wrote:

> On 2021/2/25 16:25, Greg KH wrote:
> > On Mon, Feb 22, 2021 at 08:53:52PM +0800, Xiaoming Ni wrote:
> > > From: Thomas Gleixner <tglx@...utronix.de>
> > > 
> > > The handle_exit_race() function is defined in commit c158b461306df82
> > >   ("futex: Cure exit race"), which never returns -EBUSY. This results
> > > in a small piece of dead code in the attach_to_pi_owner() function:
> > > 
> > > 	int ret = handle_exit_race(uaddr, uval, p); /* Never return -EBUSY */
> > > 	...
> > > 	if (ret == -EBUSY)
> > > 		*exiting = p; /* dead code */
> > > 
> > > The return value -EBUSY is added to handle_exit_race() in upsteam
> > > commit ac31c7ff8624409 ("futex: Provide distinct return value when
> > > owner is exiting"). This commit was incorporated into v4.9.255, before
> > > the function handle_exit_race() was introduced, whitout Modify
> > > handle_exit_race().
> > > 
> > > To fix dead code, extract the change of handle_exit_race() from
> > > commit ac31c7ff8624409 ("futex: Provide distinct return value when owner
> > >   is exiting"), re-incorporated.
> mainline:
> ac31c7ff8624 futex: Provide distinct return value when owner is exiting
> 
> > > 
> > > Fixes: c158b461306df82 ("futex: Cure exit race")
> 
> stable linux-4.9.y
> 9c3f39860367 futex: Cure exit race
> c27f392040e2 futex: Provide distinct return value when owner is exiting
> 
> > > Cc: stable@...r.kernel.org # 4.9.258-rc1
> > > Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
> > > ---
> > >   kernel/futex.c | 6 +++---
> > >   1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > What is the git commit id of this patch in Linus's tree?
> > 
> > Also, what kernel tree(s) is this supposed to go to?
> > 
> > thanks,
> > 
> > greg k-h
> > .
> > 
> Sorry, the commit id c158b461306df82 in the patch does not exist in the
> linux-stable repository.
> The commit ID is from linux-stable-rc.
> 
> I corrected the commit id in a subsequent email, and added a branch label.
> https://lore.kernel.org/lkml/20210224100923.51315-1-nixiaoming@huawei.com/

Replied to the follow-up.

> Sorry, I forgot to use "--in-reply-to=" when I sent the update patch.
> 
> This issue occurs only in the linux-4.9.y branch v4.9.258

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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