FYI, we noticed the following commit: git://internal_merge_and_test_tree devel-catchup-201606211544 commit ea32de70041a0f9b8dbb8208a22badb73e40a8ce ("drm: Revamp connector_list protection") on test machine: vm-kbuild-1G: 2 threads qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap with 1G memory caused below changes: +------------------------------------------------------------------+------------+------------+ | | 760f1ee5ad | ea32de7004 | +------------------------------------------------------------------+------------+------------+ | boot_successes | 0 | 0 | | boot_failures | 6 | 8 | | genirq:Flags_mismatch_irq##(serial)vs.#(goldfish_pdev_bus) | 6 | 5 | | backtrace:do_sys_open | 6 | 5 | | backtrace:SyS_open | 6 | 5 | | BUG:lock_held_when_returning_to_user_space | 0 | 6 | | is_leaving_the_kernel_with_locks_still_held | 0 | 6 | | invoked_oom-killer:gfp_mask=0x | 0 | 2 | | Mem-Info | 0 | 2 | | Kernel_panic-not_syncing:Out_of_memory_and_no_killable_processes | 0 | 2 | | backtrace:btrfs_test_extent_io | 0 | 2 | | backtrace:init_btrfs_fs | 0 | 2 | | backtrace:kernel_init_freeable | 0 | 2 | +------------------------------------------------------------------+------------+------------+ [ 26.517205] Freeing unused kernel memory: 992K (ffff880003908000 - ffff880003a00000) [ 26.523433] [ 26.527208] ================================================ [ 26.532106] [ BUG: lock held when returning to user space! ] [ 26.537158] 4.7.0-rc2-00776-gea32de7 #1 Not tainted [ 26.543816] ------------------------------------------------ [ 26.548589] init/1 is leaving the kernel with locks still held! [ 26.551801] 4 locks held by init/1: [ 26.554672] #0: (drm_connector_list_srcu){......}, at: [<ffffffff81aa88c5>] drm_helper_encoder_in_use+0xa5/0x1f0 [ 26.558882] #1: (drm_connector_list_srcu){......}, at: [<ffffffff81aa88c5>] drm_helper_encoder_in_use+0xa5/0x1f0 [ 26.562997] #2: (drm_connector_list_srcu){......}, at: [<ffffffff81aa88c5>] drm_helper_encoder_in_use+0xa5/0x1f0 [ 26.567048] #3: (drm_connector_list_srcu){......}, at: [<ffffffff81aa88c5>] drm_helper_encoder_in_use+0xa5/0x1f0 [ 26.573936] systemd[1]: RTC configured in localtime, applying delta of 480 minutes to system time. [ 26.578847] random: systemd urandom read with 21 bits of entropy available [ 26.669696] systemd-default-display-manager-generator[314]: No /etc/X11/default-display-manager file, nothing to generate FYI, raw QEMU command line is: qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap -kernel /pkg/linux/x86_64-randconfig-s0-06212222/gcc-6/ea32de70041a0f9b8dbb8208a22badb73e40a8ce/vmlinuz-4.7.0-rc2-00776-gea32de7 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-kbuild-1G-11/bisect_boot-1-debian-x86_64-2015-02-07.cgz-x86_64-randconfig-s0-06212222-ea32de70041a0f9b8dbb8208a22badb73e40a8ce-20160622-129410-1s349pe-1.yaml ARCH=x86_64 kconfig=x86_64-randconfig-s0-06212222 branch=linux-devel/devel-hourly-2016062118 commit=ea32de70041a0f9b8dbb8208a22badb73e40a8ce BOOT_IMAGE=/pkg/linux/x86_64-randconfig-s0-06212222/gcc-6/ea32de70041a0f9b8dbb8208a22badb73e40a8ce/vmlinuz-4.7.0-rc2-00776-gea32de7 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-kbuild-1G/debian-x86_64-2015-02-07.cgz/x86_64-randconfig-s0-06212222/gcc-6/ea32de70041a0f9b8dbb8208a22badb73e40a8ce/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-1G-11::dhcp' -initrd /fs/sdf1/initrd-vm-kbuild-1G-11 -m 1024 -smp 2 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::23010-:22 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -device virtio-scsi-pci,id=scsi0 -drive file=/fs/sdf1/disk0-vm-kbuild-1G-11,if=none,id=hd0,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd0,scsi-id=1,lun=0 -drive file=/fs/sdf1/disk1-vm-kbuild-1G-11,if=none,id=hd1,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd1,scsi-id=1,lun=1 -drive file=/fs/sdf1/disk2-vm-kbuild-1G-11,if=none,id=hd2,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd2,scsi-id=1,lun=2 -drive file=/fs/sdf1/disk3-vm-kbuild-1G-11,if=none,id=hd3,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd3,scsi-id=1,lun=3 -drive file=/fs/sdf1/disk4-vm-kbuild-1G-11,if=none,id=hd4,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd4,scsi-id=1,lun=4 -pidfile /dev/shm/kboot/pid-vm-kbuild-1G-11 -serial file:/dev/shm/kboot/serial-vm-kbuild-1G-11 -daemonize -display none -monitor null Thanks, Xiaolong