FYI, we noticed the below changes on

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/apic
commit f5d6a52f511157c7476590532a23b5664b1ed877 ("x86/smpboot: Skip delays during SMP initialization similar to Xen")


+------------------------------------------------+------------+------------+
|                                                | 19e3d60d49 | f5d6a52f51 |
+------------------------------------------------+------------+------------+
| boot_successes                                 | 20         | 10         |
| boot_failures                                  | 2          | 12         |
| IP-Config:Auto-configuration_of_network_failed | 2          | 2          |
| BUG:kernel_boot_hang                           | 0          | 10         |
+------------------------------------------------+------------+------------+


[    0.000000] Initializing CPU#1
[    1.586595] kvm-clock: cpu 1, msr 0:13fdf041, secondary cpu clock

BUG: kernel boot hang
Elapsed time: 305
qemu-system-i386 -enable-kvm -kernel /pkg/linux/i386-randconfig-c0-05111038/gcc-4.9/be67584d15684730aeed88cab355c5de8b0491fe/vmlinuz-4.1.0-rc3-01147-gbe67584 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-kbuild-yocto-i386-3/rand_boot-1-yocto-minimal-i386.cgz-i386-randconfig-c0-05111038-be67584d15684730aeed88cab355c5de8b0491fe-1-20150512-31766-1fzr1qi.yaml ARCH=i386 kconfig=i386-randconfig-c0-05111038 branch=linux-devel/devel-cairo-smoke-201505120219 commit=be67584d15684730aeed88cab355c5de8b0491fe BOOT_IMAGE=/pkg/linux/i386-randconfig-c0-05111038/gcc-4.9/be67584d15684730aeed88cab355c5de8b0491fe/vmlinuz-4.1.0-rc3-01147-gbe67584 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-kbuild-yocto-i386/yocto-minimal-i386.cgz/i386-randconfig-c0-05111038/gcc-4.9/be67584d15684730aeed88cab355c5de8b0491fe/0 LKP_SERVER=inn earlyprintk=ttyS0,115200 systemd.log_level=err debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 console=ttyS0,115200 console=tty0 vga=normal rw ip=::::vm-kbuild-yocto-i386-3::dhcp drbd.minor_count=8'  -initrd /fs/sdc1/initrd-vm-kbuild-yocto-i386-3 -m 320 -smp 2 -device e1000,netdev=net0 -netdev user,id=net0 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -drive file=/fs/sdc1/disk0-vm-kbuild-yocto-i386-3,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-kbuild-yocto-i386-3 -serial file:/dev/shm/kboot/serial-vm-kbuild-yocto-i386-3 -daemonize -display none -monitor null 



Thanks,
Ying Huang


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