linux-kernel - Re: fix bogus hotplug cpu warning

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Message-ID: <20070828101801.GA27153@elte.hu>
Date:	Tue, 28 Aug 2007 12:18:01 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: fix bogus hotplug cpu warning


* Hugh Dickins <hugh@...itas.com> wrote:

> > so if this check triggered for the cpu-offline code it's because 
> > keventd was _not_ per-cpu (perhaps because the cpu offline code 
> > broke its affinity?). So your patch hides a real bug.
> 
> No, keventd is properly per-cpu, but the task which is calling 
> current_is_keventd() is a normal user task, so smp_processor_id() did 
> warn about it.  It wouldn't make much sense to have a function 
> current_is_keventd() if you could only call it from a keventd, would 
> it ;-?  Take a look at it (kernel/workqueue.c), I believe what it does 
> is unusual (hence that comment about being "preempt-safe") but valid.

ok, you are right indeed.

	Ingo
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