linux-kernel - Re: 3.2.38 most of the time has 100% cpu use reported

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Date:	Thu, 14 Feb 2013 05:04:07 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	tmhikaru@...il.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 3.2.38 most of the time has 100% cpu use reported

On Tue, 2013-02-12 at 00:01 -0500, tmhikaru@...il.com wrote:
> 	Okay, I finally have located the patch causing this bizzare problem
> for me. Before I discuss it, I'm going to drag out the kernel bug reporting
> guidelines and try to make a proper bug report out of this.
> 
> [1.] One line summary of the problem:
> 3.2.38 most of the time has 100% cpu use reported
> 
> [2.] Full description of the problem/report:
> Reverse applying the patch for
> 
> [9a1f08a1a192f9177d7063d903773aed800b840f] drivers/firmware/dmi_scan.c: fetch dmi version from SMBIOS if it exists
> 
> on top of a clean 3.2.38 tree makes the problem go away.
[...]
> I have to admit I have no idea what the patch I'm reversing actually does,

It changes how we look for the version of a BIOS interface (DMI or
SMBIOS).  All the code that it touches, and the version number variable,
are discarded after boot and therefore can have very limited effect on
what happens later!

> what the cpu is doing when it's stuck at 100%, nor how I would diagnose this
> further or whom I should contact.  I'd like to help anyone who wants to fix
> whatever went wrong, so please contact me.

'perf top' will tell you where the CPU is spending its time.

Ben.

-- 
Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
                                                              - Albert Camus

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