bug#34235: 0e334db6bb4b1fd1e2d72c1f3d8f004313cd9f94 (posix-timers: Fix division by zero bug). Problems with glibc.

[Alan Mackenzie]

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).