On 27.06.2024 at 04:29, Krzysztof Olędzki wrote: > On 24.06.2024 at 20:45, Guenter Roeck wrote: >> On 6/24/24 13:58, Heiner Kallweit wrote: >> [ ... ] >>> >>> Too me the issue also looks like a race. According to the OP's logs: >>> - jc42 at 0x18 is instantiated successfully >>> - jc42 at 0x19 returns -EBUSY. This is what is expected if the device >>> has been instantiated otherwise already. >>> - jc42 at 0x1a returns -EEXIST. Here two instantiations of the the same >>> device seem to collide. >>> - jc42 at 0x1b returns -EBUSY, like at 0x19. >>> >>> So it looks like referenced change isn't wrong, but reveals an >>> underlying issue with device instantiation races. >> >> It isn't just a race, though. Try to unload the at24 (or ee1004 driver >> for DDR4) and load it again, and you'll see the -EBUSY errors. Problem >> is that instantiating those drivers _always_ triggers the call to >> i2c_new_client_device() even if the jc42 device is already instantiated. >> Unloading the spd/eeprom driver doesn't unload the jc42 driver, >> so -EBUSY will be seen if the spd/eeprom driver is loaded again. >> >> I have not been able to reproduce the backtrace with my systems, but those >> are all with AMD CPUs using the piix4 driver, so timing is likely different. >> Another difference is that my systems (with DDR4) use the ee1004 driver. >> That driver instantiates the jc42 devices under a driver lock, so it is >> guaranteed that a single instantiation doesn't interfere with other >> instantiations running in parallel. > > Right, sorry for not mentioning this in the original report: > > [ 0.269013] pci 0000:00:1f.3: [8086:1c22] type 00 class 0x0c0500 > [ 0.269098] pci 0000:00:1f.3: reg 0x10: [mem 0xc3a02000-0xc3a020ff 64bit] > [ 0.269186] pci 0000:00:1f.3: reg 0x20: [io 0x3000-0x301f] > [ 0.334962] pci 0000:00:1f.3: Adding to iommu group 7 > [ 7.874736] i801_smbus 0000:00:1f.3: SMBus using PCI interrupt > > $ lspci -s 0000:00:1f.3 -vvnn > 00:1f.3 SMBus [0c05]: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller [8086:1c22] (rev 04) > Subsystem: Dell Device [1028:04de] > Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- > Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- > Interrupt: pin C routed to IRQ 19 > IOMMU group: 7 > Region 0: Memory at c3a02000 (64-bit, non-prefetchable) [size=256] > Region 4: I/O ports at 3000 [size=32] > Kernel driver in use: i801_smbus Also, here is a different trace showing a different code path, which even more suggest a race: [ 7.871973] i2c_dev: i2c /dev entries driver [ 7.878215] i2c i2c-12: 4/4 memory slots populated (from DMI) [ 7.881116] at24 12-0050: 256 byte spd EEPROM, read-only [ 7.881887] i2c i2c-12: Successfully instantiated SPD at 0x50 [ 7.894183] at24 12-0051: 256 byte spd EEPROM, read-only [ 7.895910] i2c i2c-12: Failed to register i2c client jc42 at 0x19 (-16) [ 7.896039] i2c i2c-12: Successfully instantiated SPD at 0x51 [ 7.896850] i2c i2c-12: Failed creating jc42 at 0x19 [ 7.903444] sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:1f.3/i2c-12/12-001a' [ 7.904085] at24 12-0052: 256 byte spd EEPROM, read-only [ 7.905284] Hardware name: Dell Inc. PowerEdge T110 II/0PM2CW, BIOS 2.10.0 05/24/2018 [ 7.905284] Call Trace: [ 7.905284] <TASK> [ 7.909238] dump_stack_lvl+0x37/0x4a [ 7.910488] at24 12-0053: 256 byte spd EEPROM, read-only [ 7.909855] sysfs_warn_dup+0x55/0x61 [ 7.911456] i2c i2c-12: Successfully instantiated SPD at 0x53 [ 7.911597] sysfs_create_dir_ns+0xa6/0xd2 [ 7.911597] kobject_add_internal+0xc3/0x1c0 [ 7.914606] kobject_add+0xba/0xe4 [ 7.915595] ? device_add+0x53/0x726 [ 7.915595] device_add+0x132/0x726 [ 7.916622] i2c_new_client_device+0x1ee/0x246 [ 7.916622] i2c_detect.isra.0+0x17c/0x223 [ 7.918603] ? __pfx___process_new_driver+0x10/0x10 [ 7.919603] __process_new_driver+0x17/0x1e [ 7.919603] bus_for_each_dev+0x8b/0xcf [ 7.920595] ? __pfx___process_new_driver+0x10/0x10 [ 7.920595] i2c_for_each_dev+0x2d/0x49 [ 7.922608] i2c_register_driver+0x51/0x63 [ 7.922608] ? __pfx_jc42_driver_init+0x10/0x10 [ 7.923595] do_one_initcall+0x93/0x182 [ 7.924601] kernel_init_freeable+0x1be/0x204 [ 7.924601] ? __pfx_kernel_init+0x10/0x10 [ 7.924601] kernel_init+0x15/0x110 [ 7.926609] ret_from_fork+0x23/0x35 [ 7.927602] ? __pfx_kernel_init+0x10/0x10 [ 7.927602] ret_from_fork_asm+0x1b/0x30 [ 7.927602] </TASK> [ 7.929937] kobject: kobject_add_internal failed for 12-001a with -EEXIST, don't try to register things with the same name in the same directory. [ 7.932129] i2c i2c-12: Failed to register i2c client jc42 at 0x1a (-17) [ 7.933257] i2c i2c-12: Failed creating jc42 at 0x1a Note there is no warning for 0x18 and 0x1b. # sensors|grep jc42-i2c|sort jc42-i2c-12-18 jc42-i2c-12-19 jc42-i2c-12-1a jc42-i2c-12-1b Krzysztof
