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. Best regards, Alexander [1] https://lore.kernel.org/lkml/a1cca367-52b6-a6b1-fb01-890cad39fd29@xxxxxxxx/ > > [ 3.376688] sysfs: cannot create duplicate filename > '/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBUS:01/47505500-00 > 01-0000-3130-444531454238/pci0001:00/0001:00:00.0/resource0' [ 3.385103] > CPU: 3 PID: 9 Comm: kworker/u8:0 Not tainted 5.15.0-1046-azure > #53~20.04.1-Ubuntu [ 3.389585] Hardware name: Microsoft Corporation > Virtual Machine/Virtual Machine, BIOS 090008 12/07/2018 [ 3.394663] > Workqueue: events_unbound async_run_entry_fn > [ 3.397687] Call Trace: > [ 3.399312] <TASK> > [ 3.400780] dump_stack_lvl+0x38/0x4d > [ 3.402998] dump_stack+0x10/0x16 > [ 3.406050] sysfs_warn_dup.cold+0x17/0x2b > [ 3.408476] sysfs_add_file_mode_ns+0x17b/0x190 > [ 3.411072] sysfs_create_bin_file+0x64/0x90 > [ 3.413514] pci_create_attr+0xc7/0x260 > [ 3.415827] pci_create_resource_files+0x6f/0x150 > [ 3.418455] pci_create_sysfs_dev_files+0x18/0x30 > [ 3.421136] pci_bus_add_device+0x30/0x70 > [ 3.423512] pci_bus_add_devices+0x31/0x70 > [ 3.425958] hv_pci_probe+0x4ce/0x640 > [ 3.428106] vmbus_probe+0x67/0x90 > [ 3.430121] really_probe.part.0+0xcb/0x380 > [ 3.432516] really_probe+0x40/0x80 > [ 3.434581] __driver_probe_device+0xe8/0x140 > [ 3.437119] driver_probe_device+0x23/0xb0 > [ 3.439504] __driver_attach_async_helper+0x31/0x90 > [ 3.442296] async_run_entry_fn+0x33/0x120 > [ 3.444666] process_one_work+0x225/0x3d0 > [ 3.447043] worker_thread+0x4d/0x3e0 > [ 3.449233] ? process_one_work+0x3d0/0x3d0 > [ 3.451632] kthread+0x12a/0x150 > [ 3.453583] ? set_kthread_struct+0x50/0x50 > [ 3.456103] ret_from_fork+0x22/0x30 > > Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> > --- > There has been earlier attempts to fix this problem, below are the patches > for reference of these attempts. > 1. > https://lore.kernel.org/linux-pci/20230316103036.1837869-1-alexander.stein@ > ew.tq-group.com/T/#u 2. > https://lwn.net/ml/linux-kernel/20230316091540.494366-1-alexander.stein@ew. > tq-group.com/ > > Bug details: https://bugzilla.kernel.org/show_bug.cgi?id=215515 > > drivers/pci/pci-sysfs.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > index f2909ae93f2f..a31f6f2cf309 100644 > --- a/drivers/pci/pci-sysfs.c > +++ b/drivers/pci/pci-sysfs.c > @@ -1230,6 +1230,10 @@ static int pci_create_resource_files(struct pci_dev > *pdev) if (!pci_resource_len(pdev, i)) > continue; > > + /* Check if resource already allocated and proceed no further */ > + if (pdev->res_attr[i] || pdev->res_attr_wc[i]) > + return 0; > + > retval = pci_create_attr(pdev, i, 0); > /* for prefetchable resources, create a WC mappable file */ > if (!retval && arch_can_pci_mmap_wc() && > @@ -1411,9 +1415,8 @@ static int __init pci_sysfs_init(void) > struct pci_bus *pbus = NULL; > int retval; > > - sysfs_initialized = 1; > for_each_pci_dev(pdev) { > - retval = pci_create_sysfs_dev_files(pdev); > + retval = pci_create_resource_files(pdev); > if (retval) { > pci_dev_put(pdev); > return retval; > @@ -1423,6 +1426,8 @@ static int __init pci_sysfs_init(void) > while ((pbus = pci_find_next_bus(pbus))) > pci_create_legacy_files(pbus); > > + sysfs_initialized = 1; > + > return 0; > } > late_initcall(pci_sysfs_init); -- TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht München, HRB 105018 Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider http://www.tq-group.com/
