On Mon, 2013-04-22 at 11:35 -0600, Bjorn Helgaas wrote: > On Mon, Apr 22, 2013 at 3:44 AM, Mike Qiu <qiudayu@xxxxxxxxxxxxxxxxxx> wrote: > > 于 2013/4/22 16:04, Benjamin Herrenschmidt 写道: > > > >> On Mon, 2013-04-22 at 15:41 +0800, Mike Qiu wrote: > >>> > >>> Anyway, I think it's better to remove the check code as it is useless, > >>> as it > >>> will shows that this "NULL" pci_controller pointer may happen... > >> > >> Ok. It *might* still be worth adding a BUG_ON then in pci_bus_to_host() > >> itself ... no big deal either way. > > > > OK, you mean the code will remain the same and my patch is worthless? > > > > Anyway, it will be OK for me. But I hope it can be accept for more stable > > reason. > > This is powerpc code, so I'm kibitzing here, but it was cc'd to linux-pci :) > > There should be no way to get a struct pci_bus * where bus->sysdata > (== "hose") is NULL. The sysdata pointer is always supplied to > pci_create_root_bus() (or a similar interface that calls > pci_create_root_bus()), so every root bus has a valid sysdata pointer. > And every child bus inherits the sysdata pointer of its parent (in > pci_alloc_child_bus()). Therefore, every pci_bus should have a valid > sysdata pointer. And the kernel has checked whether if sysdata is NULL after call pci_create_root_bus(). > > So I think you should just remove even the existing "if (hose == > NULL)" check. That way, if bus->sysdata actually *does* turn out to > be NULL, we'll oops on the null pointer dereference, get a nice > backtrace, and have a chance to fix the problem. Testing and > returning an error means whatever bug or memory corruption caused the > null pointer will most likely be ignored. > Yes, I agree with you, because it is useless, and meaningless. Also it never achieve its goals even if the "hose==NULL". So I suggest either use my patch or remove that check code. If the second case, I will write v2 patch to remove that check code. I don't know what's to go for next step, it depends on the maintainer :) Thanks Mike > Bjorn > -- > 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 > -- 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
