linux-kernel - Re: [PATCH] pci: Make pci

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Message-ID: <20091205043635.GA10777@ldl.fc.hp.com>
Date:	Fri, 4 Dec 2009 21:36:35 -0700
From:	Alex Chiang <achiang@...com>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>, linux-pci@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] pci: Make pci_dev struct point to NULL.

* Rakib Mullick <rakib.mullick@...il.com>:
> On 12/5/09, Alex Chiang <achiang@...com> wrote:
> > * Rakib Mullick <rakib.mullick@...il.com>:
> >
> > This is from Linus's latest tree:
> >
> >   974
> >   975         if (slot->flags & SLOT_ENABLED)
> >   976                 goto err_exit;
> 
> I'm talking about this line. From here we can hit 'goto err_exit' without
> using pci_get_slot.

Right, so what's the problem? If the slot is not enabled, we goto
err_exit and return, never touching dev.

> >   977
> >   978         /* sanity check: dev should be NULL when hot-plugged in */
> >   979         dev = pci_get_slot(bus, PCI_DEVFN(slot->device, 0));
> >   980         if (dev) {
> >
> >  I assume your line 975 is my line 980.
> 
> Nope, my line 975 is also yours.
> >
> >  pci_get_slot() returns NULL if it doesn't find the devfn, so as
> >  far as I can tell, there's no need to initialize dev to NULL.
> >
> >  Were you fixing a real bug with this patch? Did you actually get
> >  the "pci_dev structure already exists.\n" error message?
> >
> No - i'm trying to make sure that we're not referencing into a trash.

I must be slow, because I don't understand how we might reference
trash.

Care to explain it to me?

Thanks,
/ac

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