linux-kernel - Regression in 4.8 - CPU speed set very low

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 9 Sep 2016 12:39:27 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     LKML <linux-kernel@...r.kernel.org>
Subject: Regression in 4.8 - CPU speed set very low

I have found a regression in kernel 4.8-rc2 that causes the speed of my laptop 
with an Intel(R) Core(TM) i7-4600M CPU @ 2.90GHz to suddenly have a maximum cpu 
frequency of ~400 MHz. Unfortunately, I do not know how to trigger this problem, 
thus a bisection is not possible. It usually happens under heavy load, such as a 
kernel build or the RPM build of VirtualBox, but it does not always fail with 
these loads. In my most recent failure, 'hwinfo --cpu' reports cpu MHz of 
396.130 for #3. The bogomips value is 5787.73, and the cpu clock before the 
fault is 3437 MHz. Nothing is logged when this happens.

If I were to get a patch that would show a backtrace when the maximum CPU 
frequency is changed, perhaps it would be possible to track this bug.

Sorry that I can not be more specific.

Larry