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Date:   Sat, 2 Feb 2019 10:44:04 +0000
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, 34235@debbugs.gnu.org,
        Eli Zaretskii <eliz@gnu.org>,
        Alex Branham <alex.branham@gmail.com>,
        Paul Eggert <eggert@cs.ucla.edu>
Subject: Re: 0e334db6bb4b1fd1e2d72c1f3d8f004313cd9f94 (posix-timers: Fix
        division by zero bug). Problems with glibc.
Message-ID: <20190202104404.GA1067@ACM>
References: <20190201214700.GA4950@ACM>
        <alpine.DEB.2.21.1902012301310.8200@nanos.tec.linutronix.de>
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From:   Alan Mackenzie <acm@muc.de>
Sender: linux-kernel-owner@vger.kernel.org
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Hello, Thomas.

Thanks for such a rapid reply!

On Fri, Feb 01, 2019 at 23:04:48 +0100, Thomas Gleixner wrote:
> Hello Alan,

> On Fri, 1 Feb 2019, Alan Mackenzie wrote:
> > 0e334db6bb4b1fd1e2d72c1f3d8f004313cd9f94
> > posix-timers: Fix division by zero bug
> > Committed: 2018-12-17 17:35:45 +0100

> > With this patch in place I am seeing problems with glibc's function
> > timer_create.  I am an Emacs maintainer, and saw these problems whilst
> > investigating Emacs bug #34235 "27.0.50; lisp profiler does not work".

> > Emacs's profiler fails in kernel 4.19.13, but works in a version of
> > 4.19.13 with the patch reversed, otherwise unchanged.  My current version
> > of glibc is 2.27-r6 (I think the "-r6" comes from Gentoo, my distro).

> Please upgrade to 4.19.19. The issue should be fixed there with the
> backported variant of

>    93ad0fc088c5 ("posix-cpu-timers: Unbreak timer rearming")

> Commit 21c0d1621b8d4b in 4.19.19

I've just built and installed Linux 4.19.19, and it does indeed solve
the Emacs profiler bug, #34235.  :-)

I see that the patch has been installed in 4.20.6, 4.19.19, and 4.14.97.
Are there any plans to install it into 4.9.x, the other live long term
support branch?  The reason I ask is to make an entry into Emacs's
PROBLEMS file, telling users and distributions which kernel versions to
upgrade to.

> Thanks,

> 	tglx

-- 
Alan Mackenzie (Nuremberg, Germany).