Greeting, FYI, we noticed the following commit (built with gcc-9): commit: ea40d7857d5250e5400f38c69ef9e17321e9c4a2 ("drm/vkms: fbdev emulation support") https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master in testcase: boot on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +-------------------------------------------------------------------+------------+------------+ | | 23fae9cf97 | ea40d7857d | +-------------------------------------------------------------------+------------+------------+ | boot_successes | 56 | 40 | | boot_failures | 0 | 20 | | WARNING:at_drivers/gpu/drm/vkms/vkms_crtc.c:#vkms_vblank_simulate | 0 | 20 | | EIP:vkms_vblank_simulate | 0 | 20 | | EIP:e1000_raise_ee_clk | 0 | 1 | | EIP:e1000_lower_ee_clk | 0 | 1 | | EIP:___might_sleep | 0 | 14 | | EIP:lock_acquire | 0 | 4 | | EIP:default_idle | 0 | 13 | | EIP:generic_exec_single | 0 | 4 | | EIP:stutter_wait | 0 | 3 | | EIP:delay_tsc | 0 | 9 | | EIP:_raw_spin_unlock_irqrestore | 0 | 5 | | EIP:torture_random | 0 | 1 | | EIP:console_unlock | 0 | 6 | | EIP:_raw_spin_unlock_irq | 0 | 3 | | EIP:_raw_spin_unlock | 0 | 1 | | EIP:kthread_should_stop | 0 | 1 | | EIP:__do_softirq | 0 | 3 | | INFO:rcu_preempt_self-detected_stall_on_CPU | 0 | 1 | | EIP:exit_to_user_mode_prepare | 0 | 1 | | EIP:acpi_ut_update_object_reference | 0 | 1 | | EIP:queued_spin_lock_slowpath | 0 | 1 | | EIP:check_preemption_disabled | 0 | 1 | | EIP:preempt_schedule_irq | 0 | 1 | | EIP:from_kuid_munged | 0 | 1 | | EIP:lock_release | 0 | 1 | | WARNING:at_net/sched/sch_generic.c:#dev_watchdog | 0 | 1 | | EIP:dev_watchdog | 0 | 1 | +-------------------------------------------------------------------+------------+------------+ If you fix the issue, kindly add following tag Reported-by: kernel test robot [ 71.976352] WARNING: CPU: 0 PID: 0 at drivers/gpu/drm/vkms/vkms_crtc.c:21 vkms_vblank_simulate+0x130/0x140 [ 71.978893] Modules linked in: uvesafb aesni_intel floppy processor evdev input_leds psmouse pcspkr [ 71.981347] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.9.0-rc5-01227-gea40d7857d525 #1 [ 72.006908] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 [ 72.009579] EIP: vkms_vblank_simulate+0x130/0x140 [ 72.010999] Code: 00 00 ff b7 4c 01 00 00 68 04 e2 54 c5 6a 02 89 55 ec 89 4d f0 e8 d0 d8 fe ff 8b 55 ec 8b 4d f0 83 c4 18 eb 80 8d 74 26 00 90 <0f> 0b e9 02 ff ff ff 8d b4 26 00 00 00 00 66 90 55 89 e5 57 56 53 [ 72.015911] EAX: 00000003 EBX: f65df328 ECX: f65df328 EDX: 00000000 [ 72.018281] ESI: 00fe4c00 EDI: 00000000 EBP: c5637e24 ESP: c5637e10 [ 72.020737] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210006 [ 72.023286] CR0: 80050033 CR2: 020cf844 CR3: 0581c000 CR4: 000406d0 [ 72.025641] Call Trace: [ 72.027494] __hrtimer_run_queues+0xb5/0x1a0 [ 72.029556] ? vkms_disable_vblank+0x10/0x10 [ 72.031643] hrtimer_interrupt+0x115/0x260 [ 72.033615] ? sysvec_call_function_single+0x30/0x30 [ 72.035676] __sysvec_apic_timer_interrupt+0x5a/0xa0 [ 72.037664] sysvec_apic_timer_interrupt+0x1a/0x30 [ 72.039653] handle_exception+0x165/0x165 [ 72.041492] EIP: default_idle+0xe/0x10 [ 72.043412] Code: 66 90 0f ae 38 0f ae f0 66 66 90 eb bc 8d b4 26 00 00 00 00 fb eb d9 8d 74 26 00 90 e9 07 00 00 00 0f 00 2d 1a 20 dc c4 fb f4 cc 55 89 e5 56 53 89 c3 e8 04 86 ff ff 89 c2 a1 7c b9 82 c5 03 [ 72.052922] EAX: 0001026e EBX: 00000000 ECX: 00000000 EDX: c55a67ed [ 72.055250] ESI: 00000000 EDI: 00000000 EBP: c5637f2c ESP: c5637f28 [ 72.057416] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00200212 [ 72.059739] ? sysvec_call_function_single+0x30/0x30 [ 72.061810] ? sysvec_call_function_single+0x30/0x30 [ 72.063965] ? default_idle+0xe/0x10 [ 72.065876] ? arch_cpu_idle+0x9/0x10 [ 72.067870] default_idle_call+0x23/0x40 [ 72.069827] do_idle+0x165/0x170 [ 72.071743] cpu_startup_entry+0x1d/0x20 [ 72.073707] rest_init+0xf8/0xfd [ 72.075527] arch_call_rest_init+0x8/0xb [ 72.077422] start_kernel+0x5f9/0x607 [ 72.079414] ? early_idt_handler_common+0x50/0x50 [ 72.081446] i386_start_kernel+0x43/0x45 [ 72.083396] startup_32_smp+0x164/0x170 [ 72.085234] ---[ end trace 9b827069a4cfe883 ]--- To reproduce: # build kernel cd linux cp config-5.9.0-rc5-01227-gea40d7857d525 .config make HOSTCC=gcc-9 CC=gcc-9 ARCH=i386 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 Thanks, Rong Chen