Greeting, FYI, we noticed the following commit (built with gcc-9): commit: 24438d18caa5149853df7da385d61747d0de7cff ("drm_print: add tracefs initialization and callback RFC") https://github.com/jimc/linux.git dd-drm-rfc in testcase: rcutorture version: with following parameters: runtime: 300s test: default torture_type: srcud test-description: rcutorture is rcutorture kernel module load/unload test. test-url: https://www.kernel.org/doc/Documentation/RCU/torture.txt on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +--------------------------------------------------------------------------+------------+------------+ | | 88cff5dfdc | 24438d18ca | +--------------------------------------------------------------------------+------------+------------+ | BUG:kernel_NULL_pointer_dereference,address | 0 | 28 | | Oops:#[##] | 0 | 28 | | RIP:strcmp | 0 | 28 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 28 | +--------------------------------------------------------------------------+------------+------------+ If you fix the issue, kindly add following tag Reported-by: kernel test robot [ 38.637741][ T1] BUG: kernel NULL pointer dereference, address: 0000000000000018 [ 38.638501][ T1] #PF: supervisor read access in kernel mode [ 38.639038][ T1] #PF: error_code(0x0000) - not-present page [ 38.639329][ T1] PGD 0 P4D 0 [ 38.639329][ T1] Oops: 0000 [#1] SMP [ 38.639329][ T1] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 5.15.0-rc3-g24438d18caa5 #1 [ 38.639329][ T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 [ 38.639329][ T1] RIP: 0010:strcmp+0xc/0x20 [ 38.639329][ T1] Code: 06 49 89 f8 48 83 c6 01 48 83 c7 01 88 47 ff 84 c0 75 eb 4c 89 c0 c3 0f 1f 80 00 00 00 00 31 c0 eb 08 48 83 c0 01 84 d2 74 0f <0f> b6 14 07 3a 14 06 74 ef 19 c0 83 c8 01 c3 31 c0 c3 66 90 48 85 [ 38.639329][ T1] RSP: 0018:ffff9ab600013e20 EFLAGS: 00010246 [ 38.639329][ T1] RAX: 0000000000000000 RBX: 0000000000000018 RCX: ffff8f0bc0168000 [ 38.639329][ T1] RDX: ffff8f0bc0168000 RSI: ffffffffbdfd2631 RDI: 0000000000000018 [ 38.639329][ T1] RBP: ffff9ab600013e50 R08: 0000000000000001 R09: 0000000000000000 [ 38.639329][ T1] R10: ffff9ab600013e18 R11: 0000000000000000 R12: ffff8f0bc02d7240 [ 38.639329][ T1] R13: 0000000000000000 R14: ffffffffba47cfa0 R15: ffffffffba74f2b0 [ 38.639329][ T1] FS: 0000000000000000(0000) GS:ffff8f0eefc00000(0000) knlGS:0000000000000000 [ 38.639329][ T1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 38.639329][ T1] CR2: 0000000000000018 CR3: 0000000213a2a000 CR4: 00000000000406b0 [ 38.639329][ T1] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 38.639329][ T1] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 38.639329][ T1] Call Trace: [ 38.639329][ T1] ? __dynamic_debug_tracer_action+0x54/0x80 [ 38.639329][ T1] ? __drm_dev_dbg+0x90/0x90 [ 38.639329][ T1] dynamic_debug_register_tracer+0x2e/0x40 [ 38.639329][ T1] ? test_drm_cmdline_init+0xb8/0xb8 [ 38.639329][ T1] drm_trace_init+0x2a/0x60 [ 38.639329][ T1] drm_core_init+0xb/0xd4 [ 38.639329][ T1] ? test_drm_cmdline_init+0xb8/0xb8 [ 38.639329][ T1] do_one_initcall+0x62/0x300 [ 38.639329][ T1] ? rcu_read_lock_sched_held+0x2c/0x60 [ 38.639329][ T1] kernel_init_freeable+0x1f2/0x24c [ 38.639329][ T1] ? rest_init+0x2a0/0x2a0 [ 38.639329][ T1] kernel_init+0x15/0x110 [ 38.639329][ T1] ret_from_fork+0x22/0x30 [ 38.639329][ T1] Modules linked in: [ 38.639329][ T1] CR2: 0000000000000018 [ 38.639329][ T1] ---[ end trace 670bae0a6915d564 ]--- [ 38.639329][ T1] RIP: 0010:strcmp+0xc/0x20 [ 38.639329][ T1] Code: 06 49 89 f8 48 83 c6 01 48 83 c7 01 88 47 ff 84 c0 75 eb 4c 89 c0 c3 0f 1f 80 00 00 00 00 31 c0 eb 08 48 83 c0 01 84 d2 74 0f <0f> b6 14 07 3a 14 06 74 ef 19 c0 83 c8 01 c3 31 c0 c3 66 90 48 85 [ 38.639329][ T1] RSP: 0018:ffff9ab600013e20 EFLAGS: 00010246 [ 38.639329][ T1] RAX: 0000000000000000 RBX: 0000000000000018 RCX: ffff8f0bc0168000 [ 38.639329][ T1] RDX: ffff8f0bc0168000 RSI: ffffffffbdfd2631 RDI: 0000000000000018 [ 38.639329][ T1] RBP: ffff9ab600013e50 R08: 0000000000000001 R09: 0000000000000000 [ 38.639329][ T1] R10: ffff9ab600013e18 R11: 0000000000000000 R12: ffff8f0bc02d7240 [ 38.639329][ T1] R13: 0000000000000000 R14: ffffffffba47cfa0 R15: ffffffffba74f2b0 [ 38.639329][ T1] FS: 0000000000000000(0000) GS:ffff8f0eefc00000(0000) knlGS:0000000000000000 [ 38.639329][ T1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 38.639329][ T1] CR2: 0000000000000018 CR3: 0000000213a2a000 CR4: 00000000000406b0 [ 38.639329][ T1] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 38.639329][ T1] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 38.639329][ T1] Kernel panic - not syncing: Fatal exception [ 38.639329][ T1] Kernel Offset: 0x38a00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) To reproduce: # build kernel cd linux cp config-5.15.0-rc3-g24438d18caa5 .config make HOSTCC=gcc-9 CC=gcc-9 ARCH=x86_64 olddefconfig prepare modules_prepare bzImage git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k job-script # job-script is attached in this email # if come across any failure that blocks the test, # please remove ~/.lkp and /lkp dir to run from a clean state. --- 0DAY/LKP+ Test Infrastructure Open Source Technology Center https://lists.01.org/hyperkitty/list/lkp(a)lists.01.org Intel Corporation Thanks, Oliver Sang