FYI, we noticed the following commit: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/vmap_stack commit a550c94136a5253a727e3af39f306b8c55b1721e ("sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") on test machine: vm-lkp-wsx03-quantal-x86_64: 2 threads qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap with 360M memory caused below changes: +------------------------------------------+------------+------------+ | | 87194cac13 | a550c94136 | +------------------------------------------+------------+------------+ | boot_successes | 47 | 0 | | boot_failures | 0 | 45 | | BUG:unable_to_handle_kernel | 0 | 39 | | Oops | 0 | 16 | | RIP:__schedule | 0 | 10 | | RIP:number | 0 | 5 | | backtrace:do_wait | 0 | 9 | | backtrace:SyS_wait4 | 0 | 9 | | PANIC:double_fault | 0 | 28 | | RIP:symbol_string | 0 | 11 | | Kernel_panic-not_syncing:Machine_halted | 0 | 28 | | WARNING:at_mm/vmalloc.c:#__vunmap | 0 | 2 | | RIP:io_serial_out | 0 | 8 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 13 | | RIP:queued_spin_lock_slowpath | 0 | 1 | | RIP:io_serial_in | 0 | 4 | | RIP:vmalloc_fault | 0 | 2 | | backtrace:smpboot_thread_fn | 0 | 2 | | RIP:__lock_acquire | 0 | 3 | | backtrace:async_run_entry_fn | 0 | 3 | | BUG:kernel_test_hang | 0 | 1 | | backtrace:compat_SyS_wait4 | 0 | 2 | | RIP:cont_add | 0 | 1 | | backtrace:core_sys_select | 0 | 1 | | backtrace:SyS_select | 0 | 1 | | backtrace:vfs_read | 0 | 1 | | backtrace:SyS_read | 0 | 1 | | RIP:no_context | 0 | 1 | | invoked_oom-killer:gfp_mask=0x | 0 | 1 | | Mem-Info | 0 | 1 | | Out_of_memory:Kill_process | 0 | 1 | | BUG:Bad_page_map_in_process | 0 | 1 | | backtrace:oom_reaper | 0 | 1 | +------------------------------------------+------------+------------+ [ 14.266586] Freeing unused kernel memory: 384K (ffff8800023a0000 - ffff880002400000) [ 14.329680] random: init urandom read with 6 bits of entropy available [ 14.417506] hwclock [ 14.420263] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420267] IP: [< (null)>] (null) [ 14.420292] PGD 0 [ 14.420321] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420357] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420359] PGD 0 [ 14.420387] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420394] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420397] PGD 0 [ 14.420424] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420451] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420454] PGD 0 [ 14.420460] BUG: unable to handle kernel NULL p [ 14.420487] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420490] PGD 0 [ 14.420517] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420524] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420526] PGD 0 [ 14.420552] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420559] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420582] PGD 0 [ 14.420588] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420615] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420618] PGD 0 [ 14.420645] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420651] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420654] PGD 0 [ 14.420681] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420687] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420710] PGD 0 [ 14.420716] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420744] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420746] PGD 0 [ 14.420752] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420779] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420782] PGD 0 [ 14.420809] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420815] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420818] PGD 0 [ 14.420845] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420872] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420875] PGD 0 [ 14.420881] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420908] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420910] PGD 0 [ 14.420938] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420944] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.420946] PGD 0 [ 14.420973] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.420980] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.421003] PGD 0 [ 14.421009] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.421036] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.421039] PGD 0 [ 14.421045] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.421110] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.421134] PGD 0 [ 14.421140] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.421168] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.421170] PGD 0 [ 14.421197] BUG: unable to handle kernel NULL pointer dereference at (null) [ 14.421204] IP: [<ffffffff8103d7fd>] no_context+0x2c5/0x382 [ 14.421206] PGD 0 [ 14.421234] BUG: unable to handle kernel [ 14.454361] BUG: unable to handle kernel [ 14.454362] PANIC: double fault, error_code: 0x0 [ 14.454370] CPU: 0 PID: 158 Comm: hwclock Not tainted 4.7.0-rc4-00259-ga550c94 #334 [ 14.454393] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 14.454397] task: ffff88000cbe4440 ti: ffff88000cbe4440 task.ti: ffff88000cbe4440 [ 14.454432] RIP: 0010:[<ffffffff815117c8>] [<ffffffff815117c8>] io_serial_out+0x15/0x17 [ 14.454435] RSP: 0018:ffffc90000150ad0 EFLAGS: 00010002 [ 14.454459] RAX: 0000000000000070 RBX: ffffffff83448380 RCX: 0000000000000000 [ 14.454462] RDX: 00000000000003f8 RSI: 0000000000000000 RDI: ffffffff83448380 [ 14.454465] RBP: ffffc90000150ad0 R08: 0000000000000002 R09: 0000000000000000 [ 14.454489] R10: ffffc90000150d18 R11: ffffffff832c5d67 R12: 0000000000000070 [ 14.454492] R13: ffffffff83448380 R14: ffffffff8151213a R15: 0000000000000059 [ 14.454496] FS: 0000000000000000(0000) GS:ffff880013c00000(0000) knlGS:0000000000000000 [ 14.454499] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 14.454522] CR2: ffffc90000150ac8 CR3: 000000000240b000 CR4: 00000000000006f0 [ 14.454531] Stack: [ 14.454560] [ 14.454561] Call Trace: [ 14.454586] <UNK> [ 14.454749] Code: 8f d9 00 00 00 8b 57 48 55 48 89 e5 d3 e6 01 f2 ec 0f b6 c0 5d c3 0f b6 8f d9 00 00 00 89 d0 8b 57 48 55 48 89 e5 d3 e6 01 f2 ee <5d> c3 8a 97 da 00 00 00 55 48 c7 87 58 02 00 00 64 16 51 81 48 [ 14.454752] Kernel panic - not syncing: Machine halted. [ 16.562053] Shutting down cpus with NMI [ 16.562640] Kernel Offset: disabled FYI, raw QEMU command line is: qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap -kernel /pkg/linux/x86_64-acpi-redef/gcc-6/a550c94136a5253a727e3af39f306b8c55b1721e/vmlinuz-4.7.0-rc4-00259-ga550c94 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-lkp-wsx03-quantal-x86_64-2/bisect_boot-1-quantal-core-x86_64.cgz-x86_64-acpi-redef-a550c94136a5253a727e3af39f306b8c55b1721e-20160626-107935-1evi98y-0.yaml ARCH=x86_64 kconfig=x86_64-acpi-redef branch=linux-devel/devel-catchup-201606260900 commit=a550c94136a5253a727e3af39f306b8c55b1721e BOOT_IMAGE=/pkg/linux/x86_64-acpi-redef/gcc-6/a550c94136a5253a727e3af39f306b8c55b1721e/vmlinuz-4.7.0-rc4-00259-ga550c94 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-lkp-wsx03-quantal-x86_64/quantal-core-x86_64.cgz/x86_64-acpi-redef/gcc-6/a550c94136a5253a727e3af39f306b8c55b1721e/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-quantal-x86_64-2::dhcp drbd.minor_count=8' -initrd /fs/sdc1/initrd-vm-lkp-wsx03-quantal-x86_64-2 -m 360 -smp 2 -device e1000,netdev=net0 -netdev user,id=net0 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -pidfile /dev/shm/kboot/pid-vm-lkp-wsx03-quantal-x86_64-2 -serial file:/dev/shm/kboot/serial-vm-lkp-wsx03-quantal-x86_64-2 -daemonize -display none -monitor null Thanks, Kernel Test Robot