On Mon, Sep 27, 2021 at 07:00:23PM +0300, Leon Romanovsky wrote: > On Mon, Sep 27, 2021 at 12:01:19PM -0300, Jason Gunthorpe wrote: > > On Mon, Sep 27, 2021 at 01:46:31PM +0000, Shameerali Kolothum Thodi wrote: > > > > > > > > Nope, this is locked wrong and has no lifetime management. > > > > > > > > > > Ok. Holding the device_lock() sufficient here? > > > > > > > > You can't hold a hisi_qm pointer with some kind of lifecycle > > > > management of that pointer. device_lock/etc is necessary to call > > > > pci_get_drvdata() > > > > > > Since this migration driver only supports VF devices and the PF > > > driver will not be removed until all the VF devices gets removed, > > > is the locking necessary here? > > > > Oh.. That is really busted up. pci_sriov_disable() is called under the > > device_lock(pf) and obtains the device_lock(vf). > > Yes, indirectly, but yes. > > > > > This means a VF driver can never use the device_lock(pf), otherwise it > > can deadlock itself if PF removal triggers VF removal. > > VF can use pci_dev_trylock() on PF to prevent PF removal. no, no here, the device_lock is used in too many places for a trylock to be appropriate > > > > But you can't access these members without using the device_lock(), as > > there really are no safety guarentees.. > > > > The mlx5 patches have this same sketchy problem. > > > > We may need a new special function 'pci_get_sriov_pf_devdata()' that > > confirms the vf/pf relationship and explicitly interlocks with the > > pci_sriov_enable/disable instead of using device_lock() > > > > Leon, what do you think? > > I see pci_dev_lock() and similar functions, they are easier to > understand that specific pci_get_sriov_pf_devdata(). That is just a wrapper for device_lock - it doesnt help anything The point is to all out a different locking regime that relies on the sriov enable/disable removing the VF struct devices Jason
