FYI, we noticed the following commit (built with gcc-7): commit: 0a9efc8e562f66f927876db2effcbd6b80191476 ("sched: Basic tracking of matching tasks") https://github.com/digitalocean/linux-coresched coresched in testcase: rcutorture with following parameters: runtime: 300s test: cpuhotplug 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 2G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +-------------------------------------------------------+------------+------------+ | | 6395f75d43 | 0a9efc8e56 | +-------------------------------------------------------+------------+------------+ | boot_successes | 2 | 4 | | boot_failures | 112 | 115 | | BUG:kernel_hang_in_boot-around-mounting-root_stage | 112 | 113 | | WARNING:at_kernel/sched/sched.h:#migrate_tasks | 0 | 2 | | RIP:migrate_tasks | 0 | 2 | | WARNING:possible_circular_locking_dependency_detected | 0 | 2 | +-------------------------------------------------------+------------+------------+ If you fix the issue, kindly add following tag Reported-by: kernel test robot <rong.a.chen(a)intel.com&gt; [ 133.050138] WARNING: CPU: 1 PID: 14 at kernel/sched/sched.h:1763 migrate_tasks+0x24f/0x7a9 [ 133.060259] Modules linked in: rcutorture torture crct10dif_pclmul crc32c_intel input_leds pcspkr i2c_piix4 evdev [ 133.062468] CPU: 1 PID: 14 Comm: migration/1 Tainted: G T 5.2.0-rc1-00109-g0a9efc8 #1 [ 133.064365] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 133.066105] RIP: 0010:migrate_tasks+0x24f/0x7a9 [ 133.067087] Code: 48 ff 05 72 25 a8 05 48 8d bb f8 09 00 00 48 ff 05 4c 25 a8 05 e8 cb 5d 2c 00 4c 39 ab f8 09 00 00 74 17 48 ff 05 57 25 a8 05 <0f> 0b 48 ff 05 56 25 a8 05 48 ff 05 57 25 a8 05 49 8d bd 88 03 00 [ 133.083817] RSP: 0018:ffff8880595cfc08 EFLAGS: 00010002 [ 133.084869] RAX: ffffed100b426800 RBX: ffff88805a133c80 RCX: ffffffff81181019 [ 133.086227] RDX: ffff88805a133c80 RSI: 2000040000000000 RDI: ffff88805a134678 [ 133.087637] RBP: ffff8880595cfc60 R08: 0000000000000007 R09: 0000000000000007 [ 133.089093] R10: ffffed100b42694f R11: 0000000000000000 R12: ffff88805a133c80 [ 133.090560] R13: ffff88803ce7a100 R14: ffff8880595cfc98 R15: ffffffff83471e60 [ 133.091940] FS: 0000000000000000(0000) GS:ffff88805a100000(0000) knlGS:0000000000000000 [ 133.106073] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 133.107285] CR2: 00000000004216d0 CR3: 0000000044ec4000 CR4: 00000000000406a0 [ 133.108742] Call Trace: [ 133.109350] sched_cpu_dying+0x205/0x3d1 [ 133.110239] ? sched_cpu_starting+0x233/0x233 [ 133.111198] ? irq_work_run+0x4d/0x56 [ 133.112011] ? flush_smp_call_function_queue+0x356/0x369 [ 133.113166] ? sched_cpu_starting+0x233/0x233 [ 133.114111] cpuhp_invoke_callback+0x401/0x1675 [ 133.115082] ? _raw_spin_unlock+0x37/0x70 [ 133.115996] ? unlock_vector_lock+0x17/0x20 [ 133.116929] ? lapic_offline+0x2f/0x38 [ 133.117745] take_cpu_down+0xdb/0x180 [ 133.131667] ? multi_cpu_stop+0x14f/0x25a [ 133.132589] ? cpuhp_invoke_callback+0x1675/0x1675 [ 133.133655] multi_cpu_stop+0x156/0x25a [ 133.134507] ? cpu_stop_queue_work+0x1d4/0x1d4 [ 133.135494] cpu_stopper_thread+0x160/0x23d [ 133.136382] ? cpu_stop_create+0x55/0x55 [ 133.137182] smpboot_thread_fn+0x605/0x651 [ 133.138027] ? sort_range+0x3e/0x3e [ 133.138704] ? __kthread_parkme+0x27/0x10f [ 133.139480] ? __kthread_parkme+0xfa/0x10f [ 133.140303] kthread+0x254/0x270 [ 133.141003] ? sort_range+0x3e/0x3e [ 133.141793] ? kthread_stop+0x566/0x566 [ 133.142643] ret_from_fork+0x24/0x30 [ 133.143436] irq event stamp: 2278 [ 133.144202] hardirqs last enabled at (2277): [<ffffffff82eeeb43>] _raw_spin_unlock_irq+0x43/0x8a [ 133.151128] hardirqs last disabled at (2278): [<ffffffff812b9e48>] multi_cpu_stop+0x115/0x25a [ 133.152925] softirqs last enabled at (2114): [<ffffffff832006fa>] __do_softirq+0x6fa/0x774 [ 133.154642] softirqs last disabled at (2025): [<ffffffff81122f4b>] irq_exit+0xaf/0x161 [ 133.156292] ---[ end trace b03815f8d0d80b05 ]--- To reproduce: # build kernel cd linux cp config-5.2.0-rc1-00109-g0a9efc8 .config make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 olddefconfig make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 prepare make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 modules_prepare make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 SHELL=/bin/bash make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 bzImage git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email Thanks, Rong Chen