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ACPI / hotplug / PCI: Avoid doing too much for spurious notifies

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Sometimes we may get a spurious device check or bus check notify for
a hotplug device and in those cases we should avoid doing all of the
configuration work needed when something actually changes.  To that
end, check the return value of pci_scan_slot() in enable_slot() and
bail out early if it is 0.

This turns out to help reduce the amount of diagnostic output from
the ACPIPHP subsystem and speed up boot on at least one system that
generates multiple device check notifies for PCIe devices on the root
bus during boot.

Reported-and-tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2013-09-06 15:41:32 +02:00
parent 89ec2f2ee1
commit 2dc41281b1
1 changed files with 6 additions and 3 deletions
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9
drivers/pci/hotplug/acpiphp_glue.c
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@ -542,12 +542,12 @@ static void __ref enable_slot(struct acpiphp_slot *slot)
struct acpiphp_func *func;
int max, pass;
LIST_HEAD(add_list);
int nr_found;
list_for_each_entry(func, &slot->funcs, sibling)
acpiphp_bus_add(func_to_handle(func));
pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
nr_found = pci_scan_slot(bus, PCI_DEVFN(slot->device, 0));
max = acpiphp_max_busnr(bus);
for (pass = 0; pass < 2; pass++) {
list_for_each_entry(dev, &bus->devices, bus_list) {
@ -566,8 +566,11 @@ static void __ref enable_slot(struct acpiphp_slot *slot)
}
}
}
__pci_bus_assign_resources(bus, &add_list, NULL);
/* Nothing more to do here if there are no new devices on this bus. */
if (!nr_found && (slot->flags & SLOT_ENABLED))
return;
acpiphp_sanitize_bus(bus);
acpiphp_set_hpp_values(bus);
acpiphp_set_acpi_region(slot);