From: Lee Jones <lee.jones@linaro.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Zheng Yejian <zhengyejian1@huawei.com>,
stable@vger.kernel.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de, cj.chengjian@huawei.com,
judy.chenhui@huawei.com, zhangjinhao2@huawei.com,
nixiaoming@huawei.com
Subject: Re: [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi_owner()
Date: Wed, 10 Mar 2021 13:28:02 +0000 [thread overview]
Message-ID: <20210310132802.GP701493@dell> (raw)
In-Reply-To: <YEi08Dr3cgNp0KlP@kroah.com>
On Wed, 10 Mar 2021, Greg KH wrote:
> On Tue, Mar 09, 2021 at 06:14:37PM +0000, Lee Jones wrote:
> > 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@linutronix.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@vger.kernel.org # v4.9.258
> > > > Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
> > > > Reviewed-by: Lee Jones <lee.jones@linaro.org>
> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > > Signed-off-by: Zheng Yejian <zhengyejian1@huawei.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")
>
> That wasn't obvious :(
This was also my thinking, which is why I replied to the original
patch in an attempt to clarify what I thought was happening.
> Is this a backport of another patch in the stable tree somewhere?
Yes, it looks like it.
The full patch was back-ported to v4.14 as:
e6e00df182908f34360c3c9f2d13cc719362e9c0
--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog
next prev parent reply other threads:[~2021-03-10 13:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 3:06 [PATCH 4.4 0/3] Backport patch series to update Futex from 4.9 Zheng Yejian
2021-03-09 3:06 ` [PATCH 4.4 1/3] futex: Change locking rules Zheng Yejian
2021-03-09 10:40 ` Greg KH
2021-03-09 3:06 ` [PATCH 4.4 2/3] futex: Cure exit race Zheng Yejian
2021-03-09 3:06 ` [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi_owner() Zheng Yejian
2021-03-09 10:40 ` Greg KH
2021-03-09 18:14 ` Lee Jones
2021-03-10 12:00 ` Greg KH
2021-03-10 13:28 ` Lee Jones [this message]
2021-03-10 14:10 ` Greg KH
2021-03-11 1:39 ` Zhengyejian (Zetta)
2021-03-09 10:41 ` [PATCH 4.4 0/3] Backport patch series to update Futex from 4.9 Greg KH
2021-03-11 3:48 ` Zhengyejian (Zetta)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210310132802.GP701493@dell \
--to=lee.jones@linaro.org \
--cc=cj.chengjian@huawei.com \
--cc=gregkh@linuxfoundation.org \
--cc=judy.chenhui@huawei.com \
--cc=linux-kernel@vger.kernel.org \
--cc=nixiaoming@huawei.com \
--cc=stable@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=zhangjinhao2@huawei.com \
--cc=zhengyejian1@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).