linux-kernel - Re: [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi

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Message-ID: <20210309181437.GV4931@dell>
Date:   Tue, 9 Mar 2021 18:14:37 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Zheng Yejian <zhengyejian1@...wei.com>, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        cj.chengjian@...wei.com, judy.chenhui@...wei.com,
        zhangjinhao2@...wei.com, nixiaoming@...wei.com
Subject: Re: [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi_owner()

On Tue, 09 Mar 2021, Greg KH wrote:

> On Tue, Mar 09, 2021 at 11:06:05AM +0800, Zheng Yejian wrote:
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > The handle_exit_race() function is defined in commit 9c3f39860367
> >  ("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.
> > 
> > Lee writes:
> > 
> > This commit takes the remaining functional snippet of:
> > 
> >  ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting")
> > 
> > ... and is the correct fix for this issue.
> > 
> > Fixes: 9c3f39860367 ("futex: Cure exit race")
> > Cc: stable@...r.kernel.org # v4.9.258
> > Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
> > Reviewed-by: Lee Jones <lee.jones@...aro.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
> > ---
> >  kernel/futex.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> Same here, what is the upstream git id?

It doesn't have one as such - it's a part-patch:

> > This commit takes the remaining functional snippet of:
> > 
> >  ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting")

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