linux-kernel - Re: [PATCH 2/2] proc: Add /proc/<pid>/timerslack

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Message-ID: <7d7579a1-2616-0437-5319-23190906a2b4@linux.intel.com>
Date:	Thu, 14 Jul 2016 06:42:04 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>,
	Kees Cook <keescook@...omium.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>,
	Oren Laadan <orenl@...lrox.com>,
	Ruchi Kandoi <kandoiruchi@...gle.com>,
	Rom Lemarchand <romlem@...roid.com>,
	Android Kernel Team <kernel-team@...roid.com>,
	Todd Kjos <tkjos@...gle.com>, Colin Cross <ccross@...roid.com>,
	Nick Kralevich <nnk@...gle.com>,
	Dmitry Shmidt <dimitrysh@...gle.com>,
	Elliott Hughes <enh@...gle.com>
Subject: Re: [PATCH 2/2] proc: Add /proc/<pid>/timerslack_ns interface

On 7/14/2016 5:48 AM, Serge E. Hallyn wrote:

> Can someone give a detailed explanation of what you could do with
> the new timerslack feature and compare it to what you can do with
> sys_nice?
>

what you can do with the timerslack feature is add upto 4 seconds of extra
time/delay on top of each select()/poll()/nanosleep()/... (basically anything that
uses hrtimers on behalf of the user), and then also control within that
4 second window exactly when that extra delay ends
(which may help a timing attack kind of scenario)