> -----Original Message----- > From: Dexuan Cui > Sent: Tuesday, September 13, 2016 2:51 AM > To: Long Li <longli@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; > Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Bjorn Helgaas > <bhelgaas@xxxxxxxxxx> > Cc: devel@xxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux- > pci@xxxxxxxxxxxxxxx > Subject: RE: [PATCH 2/2] pci-hyperv: properly handle device eject > > > From: devel [mailto:driverdev-devel-bounces@xxxxxxxxxxxxxxxxxxxxxx] On > > Behalf Of Long Li > > Sent: Tuesday, September 13, 2016 7:54 ... > > A PCI_EJECT message can arrive at the same time we are calling > > pci_scan_child_bus in the workqueue for the previous > PCI_BUS_RELATIONS > > message, in this case we could potentailly modify the bus from two places. > > Properly lock the bus access. > > > > --- a/drivers/pci/host/pci-hyperv.c > > +++ b/drivers/pci/host/pci-hyperv.c > > @@ -1587,7 +1587,7 @@ static void hv_eject_device_work(struct > > work_struct > > *work) > > pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain, > 0, > > wslot); > > if (pdev) { > > - pci_stop_and_remove_bus_device(pdev); > > + pci_stop_and_remove_bus_device_locked(pdev); > > pci_dev_put(pdev); > > } > > The _locked version tries to get the mutex pci_rescan_remove_lock. > > But it looks pci_scan_child_bus() doesn't try to get the mutex(?), so how can > this patch make sure the 2 code paths are not running simultaneously? Thanks for the review. The lock is to protect the following call to pci_scan_child_bus() in pci_devices_present_work(): /* * Tell the core to rescan bus * because there may have been changes. */ pci_lock_rescan_remove(); pci_scan_child_bus(hbus->pci_bus); pci_unlock_rescan_remove(); This race condition has shown up in the tests. You raised a valid concern in create_root_hv_pci_bus(). There might be another race condition there. I'll look into this. > > Thanks, > -- Dexuan -- 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
