Re: [PATCH] pci: Fixing drivers/pci/search.c compilation warning.

From: Matthew Wilcox
Date: Mon Oct 27 2008 - 03:45:49 EST


On Mon, Oct 27, 2008 at 03:34:14PM +0800, Zhao, Yu wrote:
> >Erm, no, the 'dev' cannot be destroyed because the caller has a refcount
> >on it. The physical device backing it might have gone away. The dev
>
> Why does the caller have a reference count? I don't see we increase the
> reference count after the 'dev' is returned by following in
> pci_get_dev_by_id():
>
> dev = bus_find_device(&pci_bus_type, dev_start, (void *)id,
> match_pci_dev_by_id);
>
> And this 'dev' becomes the 'from' in the next loop, but it may be
> destroyed before the 'pci_dev_get(from)', isn't it?

Either you've gone back to talking about pci_find_device() [which, yes, is
vulnerable to race conditions, we know that, it's not interesting to talk
about it], or you're refusing to take it on faith that pci_get_dev_by_id()
returns a device with an increased refcount. And if you don't believe
that is true, please follow the code in bus_find_device() to prove it.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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