linux-kernel - Re: [PATCH -rt 2/5] Thread Migration Preemption

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Date:	Sat, 14 Jul 2007 21:16:46 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Steven Rostedt <rostedt@...dmis.org>,
	Christoph Lameter <clameter@....com>
Subject: Re: [PATCH -rt 2/5] Thread Migration Preemption - v2

On 07/14, Peter Zijlstra wrote:
>
> From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> 
> This patch adds the ability to protect critical sections from migration to
> another CPU without disabling preemption.
> 
> This will be useful to minimize the amount of preemption disabling for the -rt
> patch. It will help leveraging improvements brought by the local_t types in
> asm/local.h (see Documentation/local_ops.txt). Note that the updates done to
> variables protected by migrate_disable must be either atomic or protected from
> concurrent updates done by other threads.
> 
> Typical use:
> 
> migrate_disable();
> local_inc(&__get_cpu_var(&my_local_t_var));
> migrate_enable();
> 
> Which will increment the variable atomically wrt the local CPU.

I still think this patch is buggy. Perhaps I am wrong. Please look at

	http://marc.info/?l=linux-kernel&m=118417177818825

there was no any reply.

Oleg.

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