Greeting,

FYI, we noticed the following commit (built with gcc-9):

commit: fc8cae04ec02c4be4dfc7f9eb5993dcb173911a5 ("[patch 04/10] sched/hotplug: Consolidate task migration on CPU unplug")
url: https://github.com/0day-ci/linux/commits/Thomas-Gleixner/sched-Migrate-disable-support-for-RT/20200917-185532
base: https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git 848785df48835eefebe0c4eb5da7690690b0a8b7

in testcase: rcutorture
version: 
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 8G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+------------------------------------------+------------+------------+
|                                          | f8ddfce07c | fc8cae04ec |
+------------------------------------------+------------+------------+
| boot_successes                           | 4          | 0          |
| boot_failures                            | 0          | 4          |
| kernel_BUG_at_kernel/sched/core.c        | 0          | 4          |
| invalid_opcode:#[##]                     | 0          | 4          |
| RIP:sched_cpu_dying                      | 0          | 4          |
| Kernel_panic-not_syncing:Fatal_exception | 0          | 4          |
+------------------------------------------+------------+------------+


If you fix the issue, kindly add following tag
Reported-by: kernel test robot <lkp@intel.com>


[   43.499402] kernel BUG at kernel/sched/core.c:7084!
[   43.500122] invalid opcode: 0000 [#1] SMP PTI
[   43.500803] CPU: 1 PID: 15 Comm: migration/1 Not tainted 5.9.0-rc1-00127-gfc8cae04ec02c #1
[   43.501694] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
[   43.502533] RIP: 0010:sched_cpu_dying+0x153/0x160
[   43.503322] Code: 5d 5d c3 80 3d 6b 76 70 01 00 0f 85 0c ff ff ff 48 c7 c7 93 b5 53 b0 c6 05 57 76 70 01 01 e8 f6 20 fc ff 0f 0b e9 f2 fe ff ff <0f> 0b 0f 0b 0f 0b eb 86 0f 1f 44 00 00 66 66 66 66 90 55 48 89 e5
[   43.506520] RSP: 0018:ffffb1f84008bdb8 EFLAGS: 00010002
[   43.507473] RAX: ffff9a91c7c66bf0 RBX: ffff9a92ffd2b380 RCX: 0000000000000001
[   43.508725] RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffff9a92ffd2b400
[   43.509989] RBP: ffffb1f84008bdd0 R08: 0000000000000000 R09: ffff9a91c7c661c4
[   43.511268] R10: 0000000000000006 R11: 0000000000000000 R12: 0000000000000001
[   43.512539] R13: 0000000000000082 R14: ffffffffaf31d840 R15: 0000000000000003
[   43.513804] FS:  0000000000000000(0000) GS:ffff9a92ffd00000(0000) knlGS:0000000000000000
[   43.515154] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   43.516116] CR2: 00007f6bc00bd000 CR3: 0000000123b00000 CR4: 00000000000406e0
[   43.517195] Call Trace:
[   43.517680]  cpuhp_invoke_callback+0x8d/0x5c0
[   43.518471]  take_cpu_down+0x60/0xa0
[   43.519125]  multi_cpu_stop+0x66/0x100
[   43.519823]  ? stop_machine_yield+0x20/0x20
[   43.520585]  cpu_stopper_thread+0x47/0x100
[   43.521329]  ? smpboot_thread_fn+0x26/0x1e0
[   43.522075]  smpboot_thread_fn+0x10b/0x1e0
[   43.522809]  ? sort_range+0x20/0x20
[   43.523454]  kthread+0x114/0x160
[   43.524031]  ? kthread_park+0xa0/0xa0
[   43.524688]  ret_from_fork+0x22/0x30
[   43.525326] Modules linked in: rcutorture torture bochs_drm sr_mod drm_vram_helper drm_ttm_helper ttm cdrom intel_rapl_msr drm_kms_helper sg syscopyarea intel_rapl_common ppdev crct10dif_pclmul sysfillrect crc32_pclmul sysimgblt crc32c_intel ghash_clmulni_intel fb_sys_fops ata_generic joydev ata_piix i2c_piix4 serio_raw drm libata parport_pc ipmi_devintf ipmi_msghandler parport ip_tables
[   43.531206] ---[ end trace fbf810d4e6a3750f ]---


To reproduce:

        # build kernel
	cd linux
	cp config-5.9.0-rc1-00127-gfc8cae04ec02c .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 <bzImage> job-script # job-script is attached in this email



Thanks,
lkp