On Fri, 2018-08-17 at 11:25 -0500, Bjorn Helgaas wrote: > On Fri, Aug 17, 2018 at 02:48:58PM +1000, Benjamin Herrenschmidt wrote: > > This re-fixes the bug reported by Hari Vyas <hari.vyas@xxxxxxxxxxxx> > > after my revert of his commit but in a much simpler way. > > > > The main issues is that is_added was being set after the driver > > got bound and started, and thus setting it could race with other > > changes to struct pci_dev. > > The "bind driver, then set dev->added = 1" order seems to have been > there since the beginning of dev->is_added: > > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8a1bc9013a03 > > This patch seems reasonable, but I'm a little dubious about the > existence of "is_added" in the first place. As far as I can tell, the > only other buses with something similar are the MEN Chameleon bus and > the Intel Management Engine Interface. > > The PCI uses of "is_added" don't seem *that* critical or unique to > PCI, so I'm not 100% convinced we need it at all. But I haven't > looked into it enough to be able to propose an alternative. This is a whole different conversation you are taking us into :-) is_added is currently needed for a number of reasons, mostly relating to partial hotplug, and historically comes from the fact that we separated the PCI probing & tree construction from the registration with the device-model. This of course comes from the fact that the device model didn't actually exist yet when the PCI code was created :-) So let's keep things separate shall we ? I'd rather fix this correctly now, and get rid of that pesky atomic priv_flags which I think is just going to be a long term add to the mess rather than an improvement, and separately we can discuss whether is_added is something that can go away, but I suspect this will come in the form of either a deeper rework of how we do PCI probing, or simply finding a struct device/kobj field we can use as a hint that we've added the device already for hotplug. > > This fixes it by setting the flag first, which also has the > > advantage of matching the fact that we are clearing it *after* > > unbinding in the remove path, thus the flag is now symtetric > > and always set while the driver code is running. > > > > Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > > --- > > drivers/pci/bus.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c > > index 35b7fc87eac5..48ae63673aa8 100644 > > --- a/drivers/pci/bus.c > > +++ b/drivers/pci/bus.c > > @@ -321,16 +321,16 @@ void pci_bus_add_device(struct pci_dev *dev) > > pci_proc_attach_device(dev); > > pci_bridge_d3_update(dev); > > > > + dev->is_added = 1; > > dev->match_driver = true; > > retval = device_attach(&dev->dev); > > if (retval < 0 && retval != -EPROBE_DEFER) { > > + dev->is_added = 0; > > pci_warn(dev, "device attach failed (%d)\n", retval); > > pci_proc_detach_device(dev); > > pci_remove_sysfs_dev_files(dev); > > return; > > } > > - > > - dev->is_added = 1; > > } > > EXPORT_SYMBOL_GPL(pci_bus_add_device); > > > > -- > > 2.17.1 > >
