linux-kernel - Re: Changing Kernel thread priorities

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Message-ID: <BANLkTimCwRYi0YTcu1jyZO=6=yqHnBF3iA@mail.gmail.com>
Date:	Sat, 11 Jun 2011 19:16:51 +0200
From:	Remy Bohmer <linux@...mer.net>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Nicholas Mc Guire <der.herr@...r.at>,
	Peter Zijlstra <peterz@...radead.org>,
	Armin Steinhoff <armin@...inhoff.de>,
	Johannes Bauer <hannes_bauer@....at>,
	Monica Puig-Pey <puigpeym@...can.es>,
	Rolando Martins <rolando.martins@...il.com>,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Changing Kernel thread priorities

Hi,

> No, it's not. The root cause was a problem with the network softirq
> and a network driver, the softirq ->49 was a temporary workaround
> until we had enough information to find the real root cause. I wish
> I'd never committed that change at all.

Clear. Did not know it was already solved. I thought it was still an
issue. This changes things :-)

>> Race conditions that occur when a softirq preempts a related hardirq
>> what the driver did not expect or was designed for.
>
> And making it the other way round hides the problem, which is even
> worse. We want stuff to explode right away.

100% Agreed

> You can run into the same
> problem when the softirq holds a lock and the high prio irq thread
> boosts it.

OK.

Thanks for the explanation. I see no reason any more why setting the
prios default to 1 would be a bad thing.
The rest of the configuration in that case can then indeed done be
done by udev and other userland friends.

Kind regards,

Remy
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