On Tue, Dec 12, 2023 at 08:19:11AM +0100, Alexander Stein wrote: > Hi Saurabh, > > thanks for the patch. > > Am Samstag, 9. Dezember 2023, 04:46:16 CET schrieb Saurabh Sengar: > > Currently there is a race in calling pci_create_resource_files function > > from two different therads, first therad is triggered by pci_sysfs_init > > from the late initcall where as the second thread is initiated by > > pci_bus_add_devices from the respective PCI drivers probe. > > > > The synchronization between these threads relies on the sysfs_initialized > > flag. However, in pci_sysfs_init, sysfs_initialized is set right before > > calling pci_create_resource_files which is wrong as it can create race > > condition with pci_bus_add_devices threads. Fix this by setting > > sysfs_initialized flag at the end of pci_sysfs_init and direecly call the > > Small typo here: direecly -> directly > > > pci_create_resource_files function from it. > > > > There can be an additional case where driver probe is so delayed that > > pci_bus_add_devices is called after the sysfs is created by pci_sysfs_init. > > In such cases, attempting to access already existing sysfs resources is > > unnecessary. Fix this by adding a check for sysfs attributes and return > > if they are already allocated. > > > > In both cases, the consequence will be the removal of sysfs resources that > > were appropriately allocated by pci_sysfs_init following the warning below. > > I'm not sure if this is the way to go. Unfortunately I can't trigger this > error on my imx6 platform at the moment (apparently timing is off). > But reading [1] again, the most expressive way is that pci_bus_add_devices() > needs to wait until pci_sysfs_init() has passed. (I correct my self a bit in my earlier reply) The problem with waiting is that sysfs entries will be created by pci_sysfs_init already and when pci_bus_add_devices try to create it will observe that the entries are already existing and in such case PCI code will remove the sysfs entries created by pci_sysfs_init. Resulting system will be having no sysfs entries. - Saurabh
