On Tue, Dec 12, 2023 at 12:28:05AM -0800, Saurabh Singh Sengar wrote: > 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. Hi Alexander, Have you got time to check this ? Please let me know if you think there is any concern left with this patch. - Saurabh
