On Fri, May 26, 2017 at 04:58:20PM -0700, Jakub Kicinski wrote: > On Fri, 26 May 2017 18:47:26 -0500, Bjorn Helgaas wrote: > > On Mon, May 22, 2017 at 03:50:23PM -0700, Jakub Kicinski wrote: > > > PCI core sets the driver pointer before calling ->probe() and only > > > clears it after ->remove(). This means driver's ->sriov_configure() > > > callback will happily race with probe() and remove(), most likely > > > leading to BUGs, since drivers don't expect this. > > > > I guess you're referring to the pci_dev->driver pointer set by > > local_pci_probe(), and this is important because sriov_numvfs_store() > > checks that pointer, right? > > Yes, exactly. I initially thought this is how the safety of sriov > callback may have been ensured, but since the order of > local_pci_probe() and the assignment is what it is, it can't.
Right. I was hoping other subsystems would establish a convention about whether we set the ->driver pointer before or after calling the driver probe() method, but if there is one, I don't see it. local_pci_probe() and really_probe() set ->driver first, but pnp_device_probe() calls the probe() method first. Can you expand on how you reproduce this problem? The only real way I see to call ->sriov_configure() is via the sysfs entry point, and I would think user-space code would typically not touch that until after it knows the driver has claimed a device. But I can certainly imagine targeted test code that could hit this problem. Bjorn
