Hello, FYI this happens in mainline kernel 4.17.0-rc1. It at least dates back to v4.8 . [ 25.697463] [ 25.697463] Start testing find_bit() with random-filled bitmap [ 25.736615] find_next_bit: 30203201 ns, 163965 iterations [ 25.783266] find_next_zero_bit: 45554622 ns, 163716 iterations [ 25.832480] find_last_bit: 48003878 ns, 163965 iterations [ 52.050031] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1] [ 52.050031] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.17.0-rc1 #210 [ 52.050031] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 52.050031] RIP: 0010:__sanitizer_cov_trace_pc+0x65/0x66: __sanitizer_cov_trace_pc at kernel/kcov.c:111 [ 52.050031] RSP: 0000:ffff88000fd43e40 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 [ 52.050031] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000017 [ 52.050031] RDX: 0000000000000000 RSI: ffff88000fd3e000 RDI: 0000000000000002 [ 52.050031] RBP: 0000000000050000 R08: 0000000000000008 R09: 0000000000000000 [ 52.050031] R10: ffff88000fd3e000 R11: 00000000222e2c32 R12: ffffffff85565d90 [ 52.050031] R13: 0000000000030f80 R14: 0000000000030f80 R15: 0000000000000000 [ 52.050031] FS: 0000000000000000(0000) GS:ffff88001f600000(0000) knlGS:0000000000000000 [ 52.050031] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 52.050031] CR2: 0000000000000000 CR3: 0000000003c6a000 CR4: 00000000000006b0 [ 52.050031] Call Trace: [ 52.050031] find_first_bit+0x66/0x7c: find_first_bit at lib/find_bit.c:106 (discriminator 1) [ 52.050031] test_find_first_bit+0x3a/0x93 [ 52.050031] find_bit_test+0x84/0x173: find_bit_test at lib/find_bit_benchmark.c:135 [ 52.050031] ? test_find_next_and_bit+0x9b/0x9b [ 52.050031] do_one_initcall+0x18e/0x3df: do_one_initcall at init/main.c:883 [ 52.050031] ? check_kcov_mode+0x5/0x37: check_kcov_mode at kernel/kcov.c:60 [ 52.050031] ? __sanitizer_cov_trace_pc+0x2b/0x66: __sanitizer_cov_trace_pc at kernel/kcov.c:101 [ 52.050031] ? check_kcov_mode+0x5/0x37: check_kcov_mode at kernel/kcov.c:60 [ 52.050031] kernel_init_freeable+0x250/0x3a5: do_initcall_level at init/main.c:951 (inlined by) do_initcalls at init/main.c:959 (inlined by) do_basic_setup at init/main.c:977 (inlined by) kernel_init_freeable at init/main.c:1127 [ 52.050031] ? rest_init+0x13a/0x13a: kernel_init at init/main.c:1050 [ 52.050031] kernel_init+0x17/0x218: kernel_init at init/main.c:1053 [ 52.050031] ? rest_init+0x13a/0x13a: kernel_init at init/main.c:1050 [ 52.050031] ret_from_fork+0x35/0x40: ret_from_fork at arch/x86/entry/entry_64.S:418 [ 52.050031] Code: 1c 00 00 8b 8b 1c 1c 00 00 48 ff 05 d2 2d fd 04 48 8b 02 48 ff c0 48 39 c1 76 0e 48 ff 05 c8 2d fd 04 48 89 2c c2 48 89 02 5b 5d 48 8b 0c 24 40 0f b6 d6 40 0f b6 f7 31 ff 48 ff 05 e9 2d fd [ 52.050031] Kernel panic - not syncing: softlockup: hung tasks [ 52.050031] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G L 4.17.0-rc1 #210 [ 52.050031] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 52.050031] Call Trace: [ 52.050031] [ 52.050031] dump_stack+0xf3/0x135: __dump_stack at lib/dump_stack.c:77 (inlined by) dump_stack at lib/dump_stack.c:113 [ 52.050031] panic+0x173/0x440: panic at kernel/panic.c:195 [ 52.050031] watchdog_timer_fn+0x343/0x382: watchdog_timer_fn at kernel/watchdog.c:444 [ 52.050031] __hrtimer_run_queues+0x2a0/0x4c3: __run_hrtimer at kernel/time/hrtimer.c:1386 (inlined by) __hrtimer_run_queues at kernel/time/hrtimer.c:1448 [ 52.050031] hrtimer_run_queues+0xcb/0xed: hrtimer_run_queues at kernel/time/hrtimer.c:1621 [ 52.050031] run_local_timers+0x2d/0x85: run_local_timers at kernel/time/timer.c:1704 [ 52.050031] update_process_times+0x30/0x7e: update_process_times at kernel/time/timer.c:1636 [ 52.050031] tick_nohz_handler+0x141/0x19a: tick_sched_handle at kernel/time/tick-sched.c:173 (inlined by) tick_nohz_handler at kernel/time/tick-sched.c:1182 [ 52.050031] smp_apic_timer_interrupt+0x1a5/0x2c4: local_apic_timer_interrupt at arch/x86/kernel/apic/apic.c:1025 (inlined by) smp_apic_timer_interrupt at arch/x86/kernel/apic/apic.c:1050 [ 52.050031] apic_timer_interrupt+0xf/0x20: apic_timer_interrupt at arch/x86/entry/entry_64.S:863 [ 52.050031] [ 52.050031] RIP: 0010:__sanitizer_cov_trace_pc+0x65/0x66: __sanitizer_cov_trace_pc at kernel/kcov.c:111 [ 52.050031] RSP: 0000:ffff88000fd43e40 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 [ 52.050031] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000017 [ 52.050031] RDX: 0000000000000000 RSI: ffff88000fd3e000 RDI: 0000000000000002 [ 52.050031] RBP: 0000000000050000 R08: 0000000000000008 R09: 0000000000000000 [ 52.050031] R10: ffff88000fd3e000 R11: 00000000222e2c32 R12: ffffffff85565d90 [ 52.050031] R13: 0000000000030f80 R14: 0000000000030f80 R15: 0000000000000000 [ 52.050031] find_first_bit+0x66/0x7c: find_first_bit at lib/find_bit.c:106 (discriminator 1) [ 52.050031] test_find_first_bit+0x3a/0x93 [ 52.050031] find_bit_test+0x84/0x173: find_bit_test at lib/find_bit_benchmark.c:135 [ 52.050031] ? test_find_next_and_bit+0x9b/0x9b [ 52.050031] do_one_initcall+0x18e/0x3df: do_one_initcall at init/main.c:883 [ 52.050031] ? check_kcov_mode+0x5/0x37: check_kcov_mode at kernel/kcov.c:60 [ 52.050031] ? __sanitizer_cov_trace_pc+0x2b/0x66: __sanitizer_cov_trace_pc at kernel/kcov.c:101 [ 52.050031] ? check_kcov_mode+0x5/0x37: check_kcov_mode at kernel/kcov.c:60 [ 52.050031] kernel_init_freeable+0x250/0x3a5: do_initcall_level at init/main.c:951 (inlined by) do_initcalls at init/main.c:959 (inlined by) do_basic_setup at init/main.c:977 (inlined by) kernel_init_freeable at init/main.c:1127 [ 52.050031] ? rest_init+0x13a/0x13a: kernel_init at init/main.c:1050 [ 52.050031] kernel_init+0x17/0x218: kernel_init at init/main.c:1053 [ 52.050031] ? rest_init+0x13a/0x13a: kernel_init at init/main.c:1050 [ 52.050031] ret_from_fork+0x35/0x40: ret_from_fork at arch/x86/entry/entry_64.S:418 [ 52.050031] Kernel Offset: disabled Attached the full dmesg, kconfig and reproduce scripts. Thanks, Fengguang