The pci_find_next_bus() is not hotplug safe, so introduce PCI hotplug safe interfaces to walk PCI buses. To avoid some deadlock scenarios, two interfaces are introduced. The first one is pci_for_each_bus(), which walks all PCI buses holding read lock on the pci_bus_sem. The second one is pci_for_each_started_bus(), which walks all started PCI buses without holding any global locks. Started PCI buses are those which have been added to the device tree by calling device_add(). --- Hi Bjorn, How about this PCI bus iterator design? It's a little ugly that we need to two interfaces to work around some deadlock scenarios. And I plan to split the task into two parts: 1) a hotplug safe PCI bus iteraror to replace pci_find_next_bus 2) handle hotplug notifications to update bus related states. My patchset at http://www.spinics.net/lists/linux-pci/msg17515.html has patially solved issue 2 above for x86/ACPI, and will add more supports for other platforms. Thanks! Gerry --- drivers/pci/bus.c | 42 ++++++++++++++++++++++++++++++++++++++++++ include/linux/pci.h | 1 + 2 files changed, 43 insertions(+) diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c index e16a8f0f..21b0ade 100644 --- a/drivers/pci/bus.c +++ b/drivers/pci/bus.c @@ -327,6 +327,48 @@ void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), } EXPORT_SYMBOL_GPL(pci_walk_bus); +static int pci_bus_iter(struct pci_bus *bus, + int (* cb)(struct pci_bus *, void *), void *data) +{ + int rc; + + rc = cb(bus, data); + if (rc == 0) + list_for_each_entry(bus, &bus->children, node) { + rc = pci_bus_iter(bus, cb, data); + if (rc) + break; + } + + return rc; +} + +/** pci_for_each_bus - walk all PCI buses and call the provided callback. + * @cb callback to be called for each bus found + * @data arbitrary pointer to be passed to callback. + * + * Walk all PCI buses and call the provided callback with pci_bus_sem held. + * + * We check the return of @cb each time. If it returns anything + * other than 0, we break out. + */ +int pci_for_each_bus(int (* cb)(struct pci_bus *, void *), void *data) +{ + int rc = 0; + struct pci_bus *bus; + + down_read(&pci_bus_sem); + list_for_each_entry(bus, &pci_root_buses, node) { + rc = pci_bus_iter(bus, cb, data); + if (rc) + break; + } + up_read(&pci_bus_sem); + + return rc; +} +EXPORT_SYMBOL(pci_for_each_bus); + struct pci_bus *pci_bus_get(struct pci_bus *bus) { if (bus) diff --git a/include/linux/pci.h b/include/linux/pci.h index 3c5017d..1423a24 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1060,6 +1060,7 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), void *userdata); +int pci_for_each_bus(int (* cb)(struct pci_bus *, void *), void *data); int pci_cfg_space_size_ext(struct pci_dev *dev); int pci_cfg_space_size(struct pci_dev *dev); unsigned char pci_bus_max_busnr(struct pci_bus *bus); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
