FYI, we noticed the following commit: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master commit df1e2f56632ddf17186f7036a3bd809d3aed8fd8 ("oom_reaper: close race with exiting task") on test machine: vm-lkp-wsx03-openwrt-i386: 1 threads qemu-system-i386 -enable-kvm with 192M memory caused below changes: +------------------------------------------------+------------+------------+ | | dea6c8c672 | df1e2f5663 | +------------------------------------------------+------------+------------+ | boot_successes | 23 | 18 | | boot_failures | 3 | 8 | | invoked_oom-killer:gfp_mask=0x | 3 | 6 | | Mem-Info | 3 | 6 | | Out_of_memory:Kill_process | 3 | 6 | | backtrace:_do_fork | 1 | | | backtrace:SyS_clone | 1 | | | backtrace:process_vm_rw | 1 | | | backtrace:SyS_process_vm_readv | 1 | | | backtrace:do_execve | 2 | | | backtrace:SyS_execve | 2 | | | backtrace:pgd_alloc | 1 | | | backtrace:mm_init | 1 | | | backtrace:vfs_write | 1 | | | backtrace:SyS_write | 1 | | | BUG:unable_to_handle_kernel | 0 | 5 | | Oops | 0 | 5 | | EIP_is_at_mmput_async | 0 | 5 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 5 | | backtrace:oom_reaper | 0 | 5 | | backtrace:do_sys_open | 0 | 1 | | backtrace:SyS_open | 0 | 1 | | IP-Config:Auto-configuration_of_network_failed | 0 | 2 | +------------------------------------------------+------------+------------+ [ 82.815896] BUG: unable to handle kernel NULL pointer dereference at 00000025 [ 82.816733] IP: [<81e30134>] mmput_async+0x9/0x6b [ 82.817281] *pde = 00000000 [ 82.817628] Oops: 0002 [#1] PREEMPT DEBUG_PAGEALLOC [ 82.818169] CPU: 0 PID: 13 Comm: oom_reaper Not tainted 4.6.0-10870-gdf1e2f5 #1 [ 82.818973] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 82.819867] task: 819a2340 ti: 819a4000 task.ti: 819a4000 [ 82.820419] EIP: 0060:[<81e30134>] EFLAGS: 00010246 CPU: 0 [ 82.820988] EIP is at mmput_async+0x9/0x6b [ 82.821413] EAX: 00000001 EBX: 00000001 ECX: 00000000 EDX: 00000000 [ 82.822040] ESI: 00000000 EDI: 819a5e9c EBP: 819a5e7c ESP: 819a5e78 [ 82.822683] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 [ 82.823226] CR0: 80050033 CR2: 00000025 CR3: 00740000 CR4: 00000690 [ 82.823864] DR0: 6cd78000 DR1: 00000000 DR2: 00000000 DR3: 00000000 [ 82.824511] DR6: ffff0ff0 DR7: 00000600 [ 82.824918] Stack: [ 82.825131] 00000001 819a5eec 81ed1467 819a5e94 7de80301 00000000 00000000 00000000 [ 82.826043] 00000101 819a5edc 00000246 00000246 819a5eb0 81e5ca86 819a5edc 819a27e8 [ 82.826968] 819a27e8 00000000 000000c2 00000000 819a5edc 819a5edc 81e50726 00000000 [ 82.827881] Call Trace: [ 82.828147] [<81ed1467>] __oom_reap_task+0x178/0x185 [ 82.828676] [<81e5ca86>] ? put_lock_stats+0xd/0x1d [ 82.829234] [<81e50726>] ? preempt_count_sub+0x8b/0xce [ 82.829771] [<81ed18c6>] oom_reaper+0x159/0x190 [ 82.830249] [<81e57fcf>] ? __wake_up_common+0x5f/0x5f [ 82.830776] [<81ed176d>] ? exit_oom_victim+0x40/0x40 [ 82.831286] [<81e496f1>] kthread+0xad/0xb2 [ 82.831722] [<8231e6a0>] ? _raw_spin_unlock_irq+0x61/0x6e [ 82.832273] [<8231eec2>] ret_from_kernel_thread+0xe/0x24 [ 82.832824] [<81e49644>] ? __kthread_parkme+0x6e/0x6e [ 82.833339] Code: 2c 50 68 a5 31 62 82 e8 9b af 09 00 58 5a a1 c4 85 9e 82 89 da e8 33 49 0d 00 8d 65 f4 5b 5e 5f 5d c3 55 89 e5 53 e8 cc f7 4e 00 48 24 74 02 eb 56 89 c3 b9 ac 85 9e 82 c7 80 4c 02 00 00 e0 [ 82.836292] EIP: [<81e30134>] mmput_async+0x9/0x6b SS:ESP 0068:819a5e78 [ 82.837000] CR2: 0000000000000025 [ 82.837342] ---[ end trace e937cb7742e041b3 ]--- [ 82.837834] Kernel panic - not syncing: Fatal exception [ 82.838374] Kernel Offset: 0x8e00000 from 0x79000000 (relocation range: 0x78000000-0x847dffff) FYI, raw QEMU command line is: qemu-system-i386 -enable-kvm -kernel /pkg/linux/i386-randconfig-x0-05271601/gcc-6/df1e2f56632ddf17186f7036a3bd809d3aed8fd8/vmlinuz-4.6.0-10870-gdf1e2f5 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-lkp-wsx03-openwrt-i386-6/rand_boot-1-openwrt-i386.cgz-i386-randconfig-x0-05271601-df1e2f56632ddf17186f7036a3bd809d3aed8fd8-20160527-94565-1mp99it-1.yaml ARCH=i386 kconfig=i386-randconfig-x0-05271601 branch=linux-next/master commit=df1e2f56632ddf17186f7036a3bd809d3aed8fd8 BOOT_IMAGE=/pkg/linux/i386-randconfig-x0-05271601/gcc-6/df1e2f56632ddf17186f7036a3bd809d3aed8fd8/vmlinuz-4.6.0-10870-gdf1e2f5 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-lkp-wsx03-openwrt-i386/openwrt-i386.cgz/i386-randconfig-x0-05271601/gcc-6/df1e2f56632ddf17186f7036a3bd809d3aed8fd8/0 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-lkp-wsx03-openwrt-i386-6::dhcp drbd.minor_count=8' -initrd /fs/sdc1/initrd-vm-lkp-wsx03-openwrt-i386-6 -m 192 -smp 1 -device e1000,netdev=net0 -netdev user,id=net0 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -drive file=/fs/sdc1/disk0-vm-lkp-wsx03-openwrt-i386-6,media=disk,if=virtio -drive file=/fs/sdc1/disk1-vm-lkp-wsx03-openwrt-i386-6,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-lkp-wsx03-openwrt-i386-6 -serial file:/dev/shm/kboot/serial-vm-lkp-wsx03-openwrt-i386-6 -daemonize -display none -monitor null Thanks, Xiaolong