> Subject: RE: [Patch v2 1/2] PCI: hv: Fix a race condition when removing the > device > > > From: Long Li <longli@xxxxxxxxxxxxx> > > Sent: Friday, April 23, 2021 11:49 AM > > To: Dexuan Cui <decui@xxxxxxxxxxxxx>; longli@xxxxxxxxxxxxxxxxx; KY > > > > > Subject: RE: [Patch v2 1/2] PCI: hv: Fix a race condition when > > > removing the device > > > > > > > From: Long Li <longli@xxxxxxxxxxxxx> > > > > Sent: Friday, April 23, 2021 11:32 AM > > > > > ... > > > > > If we test "rmmod pci-hyperv", I suspect the warning will be printed: > > > > > hv_pci_remove() -> hv_pci_bus_exit() -> > hv_pci_start_relations_work(): > > > > > > > > In most case, it will not print anything. > > > > > > If I read the code correctly, I think the warning is printed _every > > > time_ we unload pci-hyperv. > > > > Okay I see what you mean. I'll remove this message. > > Here we just want to avoid the message every time the pci-hyperv driver is > unloaded. We might want to see the possible message when the PCI device > is removed, but it's ok to me if the message is unconditionally removed. > > The real issus with the patch is that the 'hpdev' struct is never freed when > the driver is unloaded: if we print out the value of the ref counter in > put_pcichild(), we would notice that the ref counter is still two when the > driver is unloaded, i.e. memory leak occurs. > > Before the patch, hv_pci_remove() calls hv_pci_bus_exit() -> > hv_pci_start_relations_work(), and the ref counter drops to zero in > pci_devices_present_work() due to the two calls of put_pcichild(). > > With the patch, when the driver is unloaded, pci_devices_present_work() is > not scheduled, hence the ref counter doesn't drop to zero. Yes, I also see the leak, thanks to this warning message. Those will get fixed in v3.
