linux-kernel - Re: [PATCH v7 05/11] task_isolation: add debug boot flag

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Date:	Tue, 29 Sep 2015 13:35:01 -0400
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	Gilad Ben Yossef <giladb@...hip.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 05/11] task_isolation: add debug boot flag

On 09/28/2015 06:40 PM, Andy Lutomirski wrote:
> If I were writing a program that used this feature, I think I'd want
> to know early that it's not going to work so I can tell the admin very
> loudly to fix it.  Maybe just failing the prctl would be enough.  If
> someone turns on the prctl and then changes their affinity, maybe we
> should treat it as though they're just asking for trouble and allow
> it.

Yes, the original Tilera implementation required the task to be
affinitized to a single, nohz_full cpu before you could call the
prctl() successfully.  I think I will re-instate that for the patch series,
and if the user then re-affinitizes to a non-nohz_full core later,
well, "don't do that then".

-- 
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com

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