On Sun, Oct 26, 2008 at 08:51:25PM +0800, Yu Zhao wrote:This reminds me of other problems of PCI search functions.
The 'dev_start' is passed to bus_find_device(), and its 'knode_bus' reference count is decreased by klist_iter_init_node() in that function. The problem is the reference count may be already decrease to 0 because the PCI device 'from' is hot-plugged off (e.g., pci_remove_bus) when the search goes. A warning is fired when klist_iter_init_node() detects the reference count becomes 0.
Some code uses pci_find_device() in a way that is not safe with the hotplug, because a device may be destroyed after bus_find_device() returns it and before it's held by pci_dev_get() in the next round. Following is an example from a random grep:
Yes, that's why pci_find_device() is deprecated. But it doesn't also
need to be buggy ;-)