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

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Date:	Tue, 3 Feb 2009 17:58:13 +0100
From:	Frédéric Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	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>,
	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

2009/2/3 Ingo Molnar <mingo@...e.hu>:
>
> * 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.


Sorry I don't see the patch but only the changelog.
So perhaps my answer will be a bit out of sync.

But if pci_call_probe() is the only caller, so it is supposed to be
called only on boot.
Perhaps the work_on_cpu thread can be killed after boot up and then
become a thread created
on the fly after that if needed....

Or perhaps it's too much complex.....
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