linux-kernel - Re: [PATCH] fix bogus hotplug cpu warning

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Date:	Mon, 27 Aug 2007 13:52:12 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix bogus hotplug cpu warning

On Mon, 27 Aug 2007 21:37:14 +0100 (BST)
Hugh Dickins <hugh@...itas.com> wrote:

> > So I agree with the patch, but not with its description.
> 
> I don't see which part of the description you disagree with, but please
> do improve it if you can.

I'd change the description to

current_is_keventd() is a stupid load of crap.  It does

int current_is_keventd(void)
{
	struct cpu_workqueue_struct *cwq;
	int cpu = smp_processor_id();	/* preempt-safe: keventd is per-cpu */

but that comment (and the code itself) only make sense when
current_is_keventd() is called by keventd.  In which case thers is no point
in the function even existing!

We need to use raw_smp_processor_id() so that non-keventd (or, more
specifically, non-pinned-to-one-cpu) callers won't generate "using
smp_processor_id() in preemptible" warnings.

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