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Subject: Re: [PATCH 2/2] proc: Add /proc/<pid>/timerslack_ns interface
To: "Serge E. Hallyn" <serge@hallyn.com>, Kees Cook <keescook@chromium.org>
References: <1455671191-32105-1-git-send-email-john.stultz@linaro.org>
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Cc: John Stultz <john.stultz@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        lkml <linux-kernel@vger.kernel.org>, Oren Laadan <orenl@cellrox.com>,
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From: Arjan van de Ven <arjan@linux.intel.com>
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Date: Thu, 14 Jul 2016 06:42:04 -0700
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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)