Greetings, 0day kernel testing robot got the below dmesg and the first bad commit is https://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/topic/i2c_alias_device commit f6b4b47366048404b15cf71fe86e9705fd573e53 Author: Wolfram Sang <wsa+renesas(a)sang-engineering.com&gt; AuthorDate: Mon Dec 30 19:54:42 2019 +0100 Commit: Wolfram Sang <wsa(a)the-dreams.de&gt; CommitDate: Mon Dec 30 20:37:03 2019 +0100 i2c: core: add simple caching to the 'alias' scanning Add some simple caching of the last used alias to skip some unneeded scanning of the I2C bus. When freeing the device, the cache will be set back. Signed-off-by: Wolfram Sang <wsa+renesas(a)sang-engineering.com&gt; c4ebd7f2c9 i2c: core: add function to request an alias f6b4b47366 i2c: core: add simple caching to the 'alias' scanning 6b7d264865 simple test case for the I2C alias functionality +---------------------------------------------+------------+------------+------------+ | | c4ebd7f2c9 | f6b4b47366 | 6b7d264865 | +---------------------------------------------+------------+------------+------------+ | boot_successes | 31 | 0 | 0 | | boot_failures | 0 | 11 | 13 | | BUG:kernel_NULL_pointer_dereference,address | 0 | 11 | 13 | | Oops:#[##] | 0 | 11 | 13 | | EIP:i2c_unregister_device | 0 | 11 | 13 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 11 | 13 | +---------------------------------------------+------------+------------+------------+ If you fix the issue, kindly add following tag Reported-by: kernel test robot <lkp(a)intel.com&gt; [ 10.377659] OF: overlay: overlay #6 is not topmost [ 10.391238] i2c i2c-0: Added multiplexed i2c bus 1 [ 10.392328] OF: overlay: WARNING: memory leak will occur if overlay removed, property: /testcase-data/overlay-node/test-bus/i2c-test-bus/test-unittest12/status [ 10.398830] OF: overlay: WARNING: memory leak will occur if overlay removed, property: /testcase-data/overlay-node/test-bus/i2c-test-bus/test-unittest13/status [ 10.406707] i2c i2c-0: Added multiplexed i2c bus 2 [ 10.408132] BUG: kernel NULL pointer dereference, address: 00000018 [ 10.409170] #PF: supervisor read access in kernel mode [ 10.410017] #PF: error_code(0x0000) - not-present page [ 10.410897] *pdpt = 0000000000000000 *pde = f000ff53f000ff53 [ 10.411905] Oops: 0000 [#1] PREEMPT SMP PTI [ 10.412627] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G T 5.5.0-rc2-00008-gf6b4b47366048 #1 [ 10.414190] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 10.415607] EIP: i2c_unregister_device+0xf/0xf0 [ 10.416410] Code: 68 48 49 91 db 68 ac 6a c9 db e8 2c e6 6f ff 0f 0b 83 c4 0c eb c5 8d 74 26 00 90 3e 8d 74 26 00 55 31 d2 89 e5 57 56 53 85 c0 <8b> 70 18 0f 94 c2 31 c9 89 c3 b8 e8 28 02 dc 6a 00 e8 0b 12 80 ff [ 10.419548] EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000 [ 10.420597] ESI: daf7af50 EDI: 00000000 EBP: f22afd80 ESP: f22afd74 [ 10.421644] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246 [ 10.422739] CR0: 80050033 CR2: 00000018 CR3: 1c1ee000 CR4: 000406f0 [ 10.423775] Call Trace: [ 10.424223] ? devm_i2c_release_dummy+0x20/0x20 [ 10.424987] __unregister_dummy+0x18/0x30 [ 10.425655] device_for_each_child+0x57/0x90 [ 10.426367] i2c_del_adapter+0x121/0x240 [ 10.427031] i2c_mux_del_adapters+0xa0/0xe0 [ 10.430050] unittest_i2c_mux_remove+0x10/0x20 [ 10.430812] i2c_device_remove+0x3b/0x90 [ 10.431491] device_release_driver_internal+0xc6/0x180 [ 10.432443] driver_detach+0x3c/0x70 [ 10.433072] bus_remove_driver+0x40/0x90 [ 10.433739] driver_unregister+0x25/0x70 [ 10.434434] i2c_del_driver+0x1d/0x20 [ 10.435092] of_unittest+0x254e/0x2c3c [ 10.435766] ? of_unittest_dma_ranges_one+0x1e2/0x1e2 [ 10.436818] do_one_initcall+0x7a/0x3b0 [ 10.437465] ? parse_args+0x129/0x320 [ 10.438100] kernel_init_freeable+0x147/0x1d1 [ 10.438863] ? rest_init+0x110/0x110 [ 10.439494] kernel_init+0xd/0x100 [ 10.440105] ret_from_fork+0x19/0x30 [ 10.440727] Modules linked in: [ 10.441294] CR2: 0000000000000018 [ 10.441886] ---[ end trace 6dd1f183fca2df9d ]--- [ 10.442712] EIP: i2c_unregister_device+0xf/0xf0 # HH:MM RESULT GOOD BAD GOOD_BUT_DIRTY DIRTY_NOT_BAD git bisect start 6b7d26486568249ff9de6d909f27954161861c58 d1eef1c619749b2a57e514a3fa67d9a516ffa919 -- git bisect good 15c0677162b77636899ac668f3bc2055c941b9b7 # 07:26 G 10 0 0 0 dt-bindings: i2c: sh_mobile: Document r8a77961 support git bisect good da711ea086d33707190edc1f41311e55c01a7c9d # 08:04 G 10 0 0 0 i2c: core: add new variant to check for a client git bisect good c4ebd7f2c9b2ab1a75b1c48ab57081acf7b885aa # 08:27 G 10 0 0 0 i2c: core: add function to request an alias git bisect bad f6b4b47366048404b15cf71fe86e9705fd573e53 # 08:52 B 0 1 17 0 i2c: core: add simple caching to the 'alias' scanning # first bad commit: [f6b4b47366048404b15cf71fe86e9705fd573e53] i2c: core: add simple caching to the 'alias' scanning git bisect good c4ebd7f2c9b2ab1a75b1c48ab57081acf7b885aa # 09:15 G 30 0 0 0 i2c: core: add function to request an alias # extra tests with debug options # extra tests on head commit of wsa/renesas/topic/i2c_alias_device git bisect bad 6b7d26486568249ff9de6d909f27954161861c58 # 09:36 B 0 13 32 0 simple test case for the I2C alias functionality # bad: [6b7d26486568249ff9de6d909f27954161861c58] simple test case for the I2C alias functionality --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/hyperkitty/list/lkp@lists.01.org Intel Corporation