linux-kernel - Re: WARN... Device 'cpu1' does not have a release() function, it is broken and must be fixed. when doing 'xl vcpu-set <guest

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Date:	Fri, 27 Jan 2012 01:22:46 +0100
From:	Kay Sievers <kay.sievers@...y.org>
To:	Greg KH <gregkh@...e.de>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, bp@...64.org, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org, lenb@...nel.org,
	xen-devel@...ts.xensource.com
Subject: Re: WARN... Device 'cpu1' does not have a release() function, it is
 broken and must be fixed. when doing 'xl vcpu-set <guest_id> 1'

On Fri, Jan 27, 2012 at 01:06, Greg KH <gregkh@...e.de> wrote:
> On Mon, Jan 23, 2012 at 01:06:01PM -0500, Konrad Rzeszutek Wilk wrote:

>> Is anybody else hitting this with ACPI CPU hot-unplug? Or do I have
>> the privilige of being the first? Oh, I hadn't done a full bisection
>> but v3.2 does not have this.
>
> Kay, this is a mess.
>
> This cpu system device is is interconnected with the different arches
> and their cpu-specific structures.  Some arches have a static array,
> some allocate a huge structure (struct arch_cpu * NUM_CPUS), and others
> try to do the right thing with DECLARE_PER_CPU() but don't quite get it
> right, making that a static array per cpu.
>
> To unwind all of this, is much beyond 3.3 material, as I'm sure I'll get
> it wrong, and have a bunch of non-x86-64 build problems along the way.
>
> Any objection to me just doing the "hack" of the empty release function
> at the moment to get rid of this warning, and then clean it all up
> properly for 3.4?

No problem at all.

It would be nice if we get all that to the usual model some day, but I
can totally see that CPU devices try to deal with statically allocated
per-cpu memory. It seems fine, as long as they know what they are
doing.

Just silencing the driver-core warning here sounds fine to me.

Thanks,
Kay
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