Greeting,

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

commit: 52d6b926aabc47643cd910c85edb262b7f44c168 ("x86/hotplug: Silence APIC only after all interrupts are migrated")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master


in testcase: rcutorture
version: 
with following parameters:

	runtime: 300s
	test: cpuhotplug
	torture_type: rcu

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):


+------------------------------------------------------------------------------+------------+------------+
|                                                                              | d4f07268d0 | 52d6b926aa |
+------------------------------------------------------------------------------+------------+------------+
| boot_successes                                                               | 143        | 117        |
| boot_failures                                                                | 0          | 22         |
| WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_stats_print.cold[rcutorture] | 0          | 22         |
| RIP:rcu_torture_stats_print.cold[rcutorture]                                 | 0          | 22         |
+------------------------------------------------------------------------------+------------+------------+


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


[   70.096042] WARNING: CPU: 0 PID: 498 at kernel/rcu/rcutorture.c:1563 rcu_torture_stats_print.cold+0x342/0x4c0 [rcutorture]
[   70.098814] Modules linked in: rcutorture torture bochs_drm drm_vram_helper drm_ttm_helper ttm drm_kms_helper sr_mod syscopyarea sysfillrect sysimgblt cdrom fb_sys_fops drm intel_rapl_msr sg ppdev intel_rapl_common crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel ata_generic joydev serio_raw parport_pc parport ata_piix libata ipmi_devintf ipmi_msghandler i2c_piix4 ip_tables
[   70.108257] CPU: 0 PID: 498 Comm: rcu_torture_sta Not tainted 5.8.0-13576-g52d6b926aabc47 #1
[   70.110451] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
[   70.112642] RIP: 0010:rcu_torture_stats_print.cold+0x342/0x4c0 [rcutorture]
[   70.114605] Code: 00 48 0b 05 29 ff 01 00 48 0b 05 1a ff 01 00 48 0b 05 0b ff 01 00 0f 85 20 fe ff ff 83 fd 01 0f 8e 76 fe ff ff e9 12 fe ff ff <0f> 0b e9 6a fe ff ff e8 d3 dd fc f4 83 3d fc e9 c5 f5 00 0f 85 78
[   70.119208] RSP: 0018:ffffa24a005d7e00 EFLAGS: 00010202
[   70.120939] RAX: 0000000000000000 RBX: ffffa24a005d7e20 RCX: 0000000000000000
[   70.122968] RDX: 0000000000000000 RSI: ffffffffb69beca6 RDI: ffffffffb69bc86c
[   70.125010] RBP: 0000000000000001 R08: ffffffffb69beca2 R09: 0000000000000004
[   70.127046] R10: ffffffffb69bf080 R11: 00000000b69beca1 R12: ffffa24a005d7e78
[   70.129059] R13: ffffffffc0630130 R14: 0000000000000000 R15: 0000000000001997
[   70.131066] FS:  0000000000000000(0000) GS:ffff8c73ffc00000(0000) knlGS:0000000000000000
[   70.133255] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   70.135081] CR2: 00007fcdcf159000 CR3: 00000001eca8e000 CR4: 00000000000406f0
[   70.137126] Call Trace:
[   70.138410]  ? __schedule+0x34b/0x860
[   70.139514]  ? rcu_torture_stats_print+0xe0/0xe0 [rcutorture]
[   70.141272]  rcu_torture_stats+0x2a/0x60 [rcutorture]
[   70.142961]  kthread+0x114/0x160
[   70.144382]  ? kthread_park+0xa0/0xa0
[   70.145486]  ret_from_fork+0x22/0x30
[   70.146750] ---[ end trace db6662cc642dd991 ]---


To reproduce:

        # build kernel
	cd linux
	cp config-5.8.0-13576-g52d6b926aabc47 .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,
Rong Chen