linux-kernel - Re: Threading...

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Message-Id: <1169232941.3055.555.camel@laptopd505.fenrus.org>
Date:	Fri, 19 Jan 2007 19:55:41 +0100
From:	Arjan van de Ven <arjan@...radead.org>
To:	Brian McGrew <brian@...ionpro.com>
Cc:	linux-kernel@...r.kernel.org, fedora-users@...at.com
Subject: Re: Threading...

On Fri, 2007-01-19 at 10:43 -0800, Brian McGrew wrote:
> I have a very interesting question about something that we're seeing
> happening with threading between Fedora Core 3 and Fedora Core 5.  Running
> on Dell PowerEdge 1800 Hardware with a Xeon processor with hyper-threading
> turned on.  Both systems are using a 2.6.16.16 kernel (MVP al la special).
> 
> We have a multithreaded application that starts two worker threads.  On
> Fedora Core 3 both of these we use getpid() to get the PID of the thread and
> then use set_afinity to assign each thread to it's own CPU.  Both threads
> run almost symmetrically even on their given CPU watching the system
> monitor.

this is odd; even in FC3 getpid() is supposed to return the process ID
not the thread ID

> What am I missing?  What do I need to do in FC5 or the kernel or the
> threading library to get my threads to run in symmetric parallel again???

you should fix the app to use something like pthread_self() instead...
(or the highly unportable gettid() but that would just be horrible)

-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

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