linux-kernel - Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123 send_IPI_mask

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Date:	Wed, 20 Aug 2008 08:26:19 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	"the arch/x86 maintainers" <x86@...nel.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123 send_IPI_mask_bitmask+0xc3/0xe0()

On Wed, Aug 20, 2008 at 3:39 AM, Andi Kleen <andi@...stfloor.org> wrote:
> On Tue, Aug 19, 2008 at 09:51:44PM +0200, Vegard Nossum wrote:
>> Hi,
>>
>> With latest -git (1fca25427482387689fa27594c992a961d98768f), I got
>> this on reading from /dev/cpu/*/* while hot-unplugging cpu1.
>
> It's generally known the oprofile doesn't support CPU hotplug well.
> Someone needs to make a project out of fixing it properly. Right now
> it's just a "don't do that when it hurts"

Hm. What you say is true, but this one in particular has nothing to do
with oprofile! It has something to do with reading /dev/cpu/*/msr
while hot-unplugging cpu1:

 [<c011733e>] msr_read+0x6e/0xa0
 [<c01a87b4>] vfs_read+0x94/0x130

I wasn't using oprofile when this happened. So I think it should also
be considered a separate issue. Though yes -- CPU hotplug in general
tends to break a lot of things.


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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