linux-kernel - Re: High Resolution Timer DOS

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Message-ID: <75b66ecd0704281537s54134967ybc3ddef0b87b6bf5@mail.gmail.com>
Date:	Sat, 28 Apr 2007 18:37:35 -0400
From:	"Lee Revell" <rlrevell@...-job.com>
To:	tglx@...utronix.de
Cc:	"matthieu castet" <castet.matthieu@...e.fr>,
	"Linux Kernel list" <linux-kernel@...r.kernel.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: High Resolution Timer DOS

On 4/28/07, Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Well, it is not really a DoS. The rescheduling of the process is limited
> by the scheduler and the available CPU time (depending on the number of
> runnable tasks in the system).

Shouldn't an unprivileged process be rate limited somehow to avoid
flooding the machine with interrupts?  We restrict nonroot users from
setting the RTC interrupt rate higher than 64Hz for a similar reason
(granted, this limit dates back to the 486 days and should probably be
increased to 1024 Hz).

Root and SCHED_FIFO tasks could be exempt from rate limiting, to avoid
the need to introduce a new rlimit which would take years for
userspace to catch up to.

Lee
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