linux-kernel - Re: Changing Kernel thread priorities

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Message-ID: <17185480.5304.1307435255996.JavaMail.root@WARSBL214.highway.telekom.at>
Date:	Tue, 7 Jun 2011 10:27:35 +0200 (CEST)
From:	Johannes Bauer <hannes_bauer@....at>
To:	Peter Zijlstra <peterz@...radead.org>, hannes_bauer@....at
Cc:	Monica Puig-Pey <puigpeym@...can.es>,
	Rolando Martins <rolando.martins@...il.com>,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	tglx <tglx@...utronix.de>
Subject: Re: Changing Kernel thread priorities

Absolutly correct!

However, if you are running the system on an embedded platform, where the _WHOLE_ system (including priorities) is preconfigured and never touched, starting a irq thread with the right prio from start is a more straightforward method than having to invoke a script that changes it using userspace chrt tool.

Regards JB
----- Ursprüngliche Nachricht -----
Von: "Peter Zijlstra" <peterz@...radead.org>
Erhalten: 07.06.2011 00:36
An: hannes_bauer@....at

"Monica Puig-Pey" wrote:
> 
> I need to change the priority from inside the driver, when creating the 
> kernel thread.

No you don't. How does you driver know about what priority is correct
wrt all the other running RT tasks on the system?

Determining the right priority in a fixed priority scheduling system is
a system wide problem, nobody but the administrator can possibly even
begin to solve it.

There's a reason all RT irq threads are started at 50, its plain
impossible to do better.

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