Matthew Wilcox wrote:
On Mon, Oct 27, 2008 at 03:13:51PM +0800, Zhao, Yu wrote:
Matthew Wilcox wrote:
On Mon, Oct 27, 2008 at 11:18:43AM +0800, Zhao, Yu wrote:
Matthew Wilcox wrote:
Yes, that's why pci_find_device() is deprecated. But it doesn't also
need to be buggy ;-)
How about pci_get_bus_and_slot()? People would meet the problem with it
anyway.
What problem with it? It's documented to return the device with an
increased refcount, and the implementation appears to do exactly that:
The 'dev' returned by pci_get_device() may be destroyed by PCI hotplug.
I suppose that passing this 'dev' to pci_get_device() in the next loop
would crash the system, right?
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?
won't be destroyed until its reference count reaches zero, which could
be any time someone calls pci_dev_put() on it. In the scenario you're
postulating, it would happen in pci_get_dev_by_id():
if (from)
pci_dev_put(from);
which is the last time that 'from' is referred to in that callchain.
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