On Friday, October 11, 2013 11:58:48 PM Rafael J. Wysocki wrote: > On Friday, October 11, 2013 10:21:35 AM Linus Torvalds wrote: > > On Fri, Oct 11, 2013 at 4:13 AM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: [...] > > Or am I misreading the code? It's more readable, and no longer makes > > me homicidal, but I don't actually know the code itself. > > I think you're reading it correctly, it really makes acpiphp see all slots > even if pciehp sees them too. So the change is somewhat risky. > > That said the risk doesn't seem to be huge and there seem to be cases in > which it actually would be useful to have both acpiphp and pciehp signaling > available for the same device. For example, even if the BIOS told us that > we could use the native mechanism (pciehp), it may not actually work. That is, > we may not get any hotplug interrupts from PCIe ports due to platform bugs of > some sort and we may get ACPI notifications instead (because the platform > designer knew about those bugs and thought it would be smart to use ACPI to > work around them). > > There are bug reports indicating thinks like that, so we were going to allow > acpiphp and pciehp to handle the same devices anyway at one point. I thought > we might as well try to do it now and see how it goes. Still, if you think > it's too risky for this stage of the cycle, I'll just send a patch removing > the WARN_ON() and we'll revisit that thing in 3.13. Having reconsidered this I think it's best to just drop the WARN_ON() for now after all and sort out the coexistence between acpiphp and pciehp later, so that we don't run into a weird corner case late in the cycle. So the one below is what I'm going to do for 3.12. Rafael --- From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Subject: ACPI / hotplug / PCI: Drop WARN_ON() from acpiphp_enumerate_slots() The WARN_ON() in acpiphp_enumerate_slots() triggers unnecessarily for devices whose bridges are going to be handled by native PCIe hotplug (pciehp) and the simplest way to prevent that from happening is to drop the WARN_ON(). References: https://bugzilla.kernel.org/show_bug.cgi?id=62831 Reported-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> --- drivers/pci/hotplug/acpiphp_glue.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c =================================================================== --- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c +++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c @@ -999,12 +999,13 @@ void acpiphp_enumerate_slots(struct pci_ /* * This bridge should have been registered as a hotplug function - * under its parent, so the context has to be there. If not, we - * are in deep goo. + * under its parent, so the context should be there, unless the + * parent is going to be handled by pciehp, in which case this + * bridge is not interesting to us either. */ mutex_lock(&acpiphp_context_lock); context = acpiphp_get_context(handle); - if (WARN_ON(!context)) { + if (!context) { mutex_unlock(&acpiphp_context_lock); put_device(&bus->dev); kfree(bridge); -- 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
