FYI, we noticed the following commit (built with gcc-7): commit: e1056a25daa6460c95e92d7d6853d05ad62458f7 ("x86/hotplug: Silence APIC and NMI when CPU is dead") https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git WIP.x86/ipi in testcase: locktorture with following parameters: runtime: 300s test: cpuhotplug test-description: This torture test consists of creating a number of kernel threads which acquire the lock and hold it for specific amount of time, thus simulating different critical region behaviors. test-url: https://www.kernel.org/doc/Documentation/locking/locktorture.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): +----------------------------------------------------------+------------+------------+ | | c1257b49b9 | e1056a25da | +----------------------------------------------------------+------------+------------+ | boot_successes | 8 | 6 | | boot_failures | 51 | 48 | | BUG:kernel_reboot-without-warning_in_test_stage | 50 | 22 | | BUG:soft_lockup-CPU##stuck_for#s | 1 | | | RIP:__memcpy | 1 | | | Kernel_panic-not_syncing:softlockup:hung_tasks | 1 | | | WARNING:at_arch/x86/kernel/apic/apic.c:#setup_local_APIC | 0 | 26 | | RIP:setup_local_APIC | 0 | 26 | +----------------------------------------------------------+------------+------------+ If you fix the issue, kindly add following tag Reported-by: kernel test robot <rong.a.chen(a)intel.com&gt; [ 216.682229] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/apic/apic.c:1473 setup_local_APIC+0x250/0x3b0 [ 216.724190] Modules linked in: locktorture torture sr_mod cdrom ata_generic pata_acpi bochs_drm ttm ppdev drm_kms_helper ata_piix syscopyarea snd_pcm sysfillrect sysimgblt libata fb_sys_fops snd_timer snd drm crc32c_intel soundcore joydev serio_raw pcspkr i2c_piix4 parport_pc parport floppy [ 216.771348] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0-rc5-00003-ge1056a2 #1 [ 216.785027] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 216.800351] RIP: 0010:setup_local_APIC+0x250/0x3b0 [ 216.809104] Code: 30 8b 0d eb 78 7d 01 85 c9 74 26 0f 31 c1 e1 0a 48 c1 e2 20 41 89 ce 4c 03 34 24 48 09 d0 49 29 c6 4d 85 f6 0f 8f 74 fe ff ff <0f> 0b e9 22 ff ff ff 49 83 ee 01 eb ea a9 00 00 01 00 8b 15 2c ac [ 216.843098] RSP: 0000:ffffffff89a03ee0 EFLAGS: 00010082 [ 216.852617] RAX: 00000076a573f693 RBX: 0000000000000020 RCX: 0000000089ff6800 [ 216.865848] RDX: 0000007600000000 RSI: 0000000000000020 RDI: ffffffff89a03ef0 [ 216.878971] RBP: 0000000000000000 R08: ffffffff8a348de2 R09: 0000000000000032 [ 216.892080] R10: ffffffff89a03ee8 R11: 0000000000000000 R12: 00000000000000f0 [ 216.905019] R13: 0000000000001000 R14: fffffffffffc1cfb R15: 0000000000000000 [ 216.918205] FS: 0000000000000000(0000) GS:ffff89af74800000(0000) knlGS:0000000000000000 [ 216.941317] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 216.951812] CR2: 0000000057567184 CR3: 000000000ba0a000 CR4: 00000000000006f0 [ 216.964997] Call Trace: [ 216.969667] apic_ap_setup+0xa/0x20 [ 216.976266] start_secondary+0x78/0x1e0 [ 216.983423] secondary_startup_64+0xb6/0xc0 [ 216.991271] ---[ end trace 06172ec0274b1dfa ]--- To reproduce: # build kernel cd linux cp config-5.2.0-rc5-00003-ge1056a2 .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 find lib/ | cpio -o -H newc --quiet | gzip > modules.cgz bin/lkp qemu -k <bzImage> -m modules.cgz job-script # job-script is attached in this email Thanks, Rong Chen