FYI, we noticed the below changes on

commit a18b5d01819235629289212ad428a5ee2b40f0d9 ("sched: Fix missing preemption opportunity")


+------------------------------------------+------------+------------+
|                                          | 80e3d87b2c | a18b5d0181 |
+------------------------------------------+------------+------------+
| boot_successes                           | 75         | 0          |
| boot_failures                            | 0          | 52         |
| BUG:unable_to_handle_kernel              | 0          | 32         |
| Oops                                     | 0          | 32         |
| RIP:rb_reserve_next_event                | 0          | 2          |
| Kernel_panic-not_syncing:Fatal_exception | 0          | 32         |
| RIP:ftrace_push_return_trace             | 0          | 29         |
| BUG:kernel_boot_hang                     | 0          | 17         |
| BUG:Function_graph_tracer_hang           | 0          | 1          |
| PANIC:double_fault                       | 0          | 1          |
| RIP:trace_graph_entry                    | 0          | 1          |
| RIP:show_stack_log_lvl                   | 0          | 1          |
| BUG:kernel_boot_crashed                  | 0          | 3          |
+------------------------------------------+------------+------------+

[    0.572050] Testing tracer wakeup_dl: 
[    0.572050] Testing tracer wakeup_dl: PASSED
PASSED
[    0.636050] Testing tracer function_graph: 
[    0.636050] Testing tracer function_graph: 

[    0.648264] BUG: unable to handle kernel 
[    0.648264] BUG: unable to handle kernel paging requestpaging request at 00000000000013cc
 at 00000000000013cc
[    0.649716] IP:
[    0.649716] IP: [<ffffffff81113a51>] ftrace_push_return_trace+0xa3/0x11b
 [<ffffffff81113a51>] ftrace_push_return_trace+0xa3/0x11b
[    0.651015] PGD 0 
[    0.651015] PGD 0 
Elapsed time: 5
qemu-system-x86_64 -enable-kvm -kernel /kernel/x86_64-randconfig-iv0-02140421/b348a8e194ef549ebc687372e8b6e6cd2894d789/vmlinuz-3.19.0-03529-gb348a8e -append 'user=lkp job=/lkp/scheduled/vm-vp-quantal-x86_64-41/reconfirm_boot-1-quantal-core-x86_64.cgz-x86_64-randconfig-iv0-02140421-b348a8e194ef549ebc687372e8b6e6cd2894d789-20-20150215-42483-1nmui94.yaml ARCH=x86_64 BOOT_IMAGE=/kernel/x86_64-randconfig-iv0-02140421/b348a8e194ef549ebc687372e8b6e6cd2894d789/vmlinuz-3.19.0-03529-gb348a8e kconfig=x86_64-randconfig-iv0-02140421 commit=b348a8e194ef549ebc687372e8b6e6cd2894d789 branch=kvm/merge-resolution-3.20 root=/dev/ram0 max_uptime=3600 RESULT_ROOT=/result/vm-vp-quantal-x86_64/boot/1/quantal-core-x86_64.cgz/x86_64-randconfig-iv0-02140421/b348a8e194ef549ebc687372e8b6e6cd2894d789/22 ip=::::vm-vp-quantal-x86_64-41::dhcp earlyprintk=ttyS0,115200 rd.udev.log-priority=err systemd.log_target=journal systemd.log_level=warning 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 drbd.minor_count=8'  -initrd /fs/sdf1/initrd-vm-vp-quantal-x86_64-41 -m 360 -smp 2 -net nic,vlan=1,model=e1000 -net user,vlan=1 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -pidfile /dev/shm/kboot/pid-vm-vp-quantal-x86_64-41 -serial file:/dev/shm/kboot/serial-vm-vp-quantal-x86_64-41 -daemonize -display none -monitor null


Thanks,
Huang, Ying