linux-kernel - Re: [PATCH] pci: fix no_pci

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Message-ID: <19f34abd0901161121j2f5a21b5g2a73036dc20766ad@mail.gmail.com>
Date:	Fri, 16 Jan 2009 20:21:47 +0100
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Jesse Barnes" <jbarnes@...tuousgeek.org>
Cc:	"Greg KH" <gregkh@...e.de>,
	"Pekka Enberg" <penberg@...helsinki.fi>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pci: fix no_pci_devices() #2

On Fri, Jan 16, 2009 at 7:41 PM, Jesse Barnes <jbarnes@...tuousgeek.org> wrote:
>> > Assuming Greg already took the generic part, can you resend the PCI part
>> > to the linux-pci@...r.kernel.org list for review just in case anyone has
>> > a better idea of how to do it?
>>
>> Did I take the generic part?  I can't remember...
>
> Doesn't look like it.  Vergard can you send out an updated patch set?

Actually, my patch is still just a hack, since pci_bus_type.p is still
set before the pci_bus_type is really usable. So if the kernel crashes
(or, in general, no_pci_devices() is called) at some point between the
pci_bus_type.p = <something> and pci_bus_type.p = NULL (which I
inserted), we will still see the same type of fault.

So I would prefer to solve this in a different way, like a dedicated
flag which is only set after we know that pci_bus_type initialisation
succeeded. I think that was the approach of my first patch? I don't
remember. In any case, such a patch could not be split in generic/pci
parts, I think. Also, should we anticipate concurrent access to
pci_bus_type.p or such a dedicated "no_pci_devices" flag?

Here is the first patch, but I wonder if it should be turned into
atomic_t instead: http://lkml.org/lkml/2008/12/20/33

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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