linux-kernel - Re: + work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand.patch added to -mm tree

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Message-ID: <20090203121147.GB19979@elte.hu>
Date:	Tue, 3 Feb 2009 13:11:47 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Oleg Nesterov <oleg@...hat.com>, Mike Travis <travis@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frédéric Weisbecker <fweisbec@...il.com>
Cc:	mm-commits@...r.kernel.org, rusty@...tcorp.com.au
Subject: Re: +
	work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand.patch
	added to -mm tree


* akpm@...ux-foundation.org <akpm@...ux-foundation.org> wrote:

> ------------------------------------------------------
> Subject: work_on_cpu(): rewrite it to create a kernel thread on demand
> From: Andrew Morton <akpm@...ux-foundation.org>
> 
> The various implemetnations and proposed implemetnations of work_on_cpu()
> are vulnerable to various deadlocks because they all used queues of some
> form.
> 
> Unrelated pieces of kernel code thus gained dependencies wherein if one
> work_on_cpu() caller holds a lock which some other work_on_cpu() callback
> also takes, the kernel could rarely deadlock.
> 
> Fix this by creating a short-lived kernel thread for each work_on_cpu()
> invokation.
> 
> This is not terribly fast, but the only current caller of work_on_cpu() is
> pci_call_probe().

hm, it's quite ugly as well, and wasteful with resources.

	Ingo
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