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To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Alex Branham <alex.branham@gmail.com>, Alan Mackenzie <acm@muc.de>,
        Eli Zaretskii <eliz@gnu.org>, linux-kernel@vger.kernel.org,
        34235@debbugs.gnu.org
From:   Paul Eggert <eggert@cs.ucla.edu>
Subject: Re: 0e334db6bb4b1fd1e2d72c1f3d8f004313cd9f94 (posix-timers: Fix,
 division by zero bug). Problems with glibc.
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Organization: UCLA Computer Science Department
Message-ID: <17880b13-2fde-764d-a284-11cf0caf1cec@cs.ucla.edu>
Date:   Fri, 1 Feb 2019 18:07:09 -0800
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Thanks for helping to track down this bug. Since the problem occurs only 
with a few Linux kernel versions and affects Emacs only when doing CPU 
profiling, it doesn't seem worth spending time to try to patch Emacs to 
work around the bug. So I installed the attached patch into emacs-26's 
etc/PROBLEMS file to warn users about the problem, and am closing the 
Emacs bug report.


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Content-Type: text/x-patch;
 name="0001-etc-PROBLEMS-Mention-profiler-report-bug-Bug-34235.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename*0="0001-etc-PROBLEMS-Mention-profiler-report-bug-Bug-34235.patc";
 filename*1="h"

From 1243188bc4f722abf16518bf73924ce5f17750cf Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 1 Feb 2019 17:58:05 -0800
Subject: [PATCH] * etc/PROBLEMS: Mention profiler-report bug (Bug#34235).

---
 etc/PROBLEMS | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/etc/PROBLEMS b/etc/PROBLEMS
index cab087631c..00583f016d 100644
--- a/etc/PROBLEMS
+++ b/etc/PROBLEMS
@@ -1850,6 +1850,12 @@ term/xterm.el) for more details.
 
 ** GNU/Linux
 
+*** GNU/Linux: profiler-report outputs nothing.
+
+A few versions of the Linux kernel have timer bugs that break CPU
+profiling; see Bug#34235.  To fix the problem, upgrade to kernel
+versions 4.19.19 or 4.20.6, or later.
+
 *** GNU/Linux: Process output is corrupted.
 
 There is a bug in Linux kernel 2.6.10 PTYs that can cause emacs to
-- 
2.20.1


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