FYI, we noticed the following commit: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/vmap_stack commit 56c8928ebabd0c51b34056128ba686e38c867fe1 ("sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") on test machine: 1 threads qemu-system-x86_64 -enable-kvm -cpu SandyBridge with 320M memory caused below changes: +----------------------------------------------+------------+------------+ | | 09b2041c78 | 56c8928eba | +----------------------------------------------+------------+------------+ | boot_successes | 77 | 25 | | boot_failures | 0 | 53 | | WARNING:at_kernel/fork.c:#free_task | 0 | 2 | | backtrace:_do_fork | 0 | 2 | | backtrace:SyS_clone | 0 | 2 | | INFO:trying_to_register_non-static_key | 0 | 48 | | INFO:rcu_sched_detected_stalls_on_CPUs/tasks | 0 | 1 | | BUG:spinlock_lockup_suspected_on_CPU | 0 | 1 | | BUG:unable_to_handle_kernel | 0 | 49 | | Oops | 0 | 49 | | RIP:spin_dump | 0 | 1 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 49 | | backtrace:do_mount | 0 | 49 | | backtrace:SyS_mount | 0 | 49 | | backtrace:schedule_timeout | 0 | 1 | | RIP:spin_dump/#x8fket | 0 | 1 | | RIP:__list_add | 0 | 47 | | BUG:kernel_boot_hang | 0 | 1 | | RIP:__lock_acquire | 0 | 1 | +----------------------------------------------+------------+------------+ [ 36.834889] UDF-fs: error (device nbd2): udf_read_tagged: read failed, block=256, location=256 [ 36.835698] UDF-fs: error (device nbd2): udf_read_tagged: read failed, block=512, location=512 [ 36.835700] UDF-fs: warning (device nbd2): udf_fill_super: No partition found (1) [ 36.894449] INFO: trying to register non-static key. [ 36.894450] the code is fine but needs lockdep annotation. [ 36.894451] turning off the locking correctness validator. [ 36.894456] CPU: 0 PID: 817 Comm: mount Not tainted 4.7.0-rc4-00255-g56c8928 #1 [ 36.894457] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 36.894462] 0000000000000000 ffff8800299a3a98 ffffffff81776247 0000000000000000 [ 36.894465] 0000000000000001 ffff8800299a3b00 ffffffff8111ebaa ffff8800299a3ab8 [ 36.894469] ffffffff8109b058 00000000299a3ac8 ffffffff81077fe3 ffff8800299a3ad8 [ 36.894469] Call Trace: [ 36.894513] [<ffffffff81776247>] dump_stack+0x82/0xb8 [ 36.894538] [<ffffffff8111ebaa>] register_lock_class+0x142/0x2f1 [ 36.894548] [<ffffffff8109b058>] ? kvm_sched_clock_read+0x9/0x12 [ 36.894562] [<ffffffff81077fe3>] ? paravirt_sched_clock+0x9/0xd [ 36.894565] [<ffffffff81078684>] ? sched_clock+0x9/0xb [ 36.894570] [<ffffffff81121bc7>] __lock_acquire+0x15a/0xe6f [ 36.894594] [<ffffffff82eceecb>] ? _raw_spin_unlock_irq+0x2c/0x3b [ 36.894597] [<ffffffff82ecb9d8>] ? __wait_for_common+0x42/0x148 [ 36.894599] [<ffffffff8112179a>] ? trace_hardirqs_on_caller+0x17c/0x198 [ 36.894601] [<ffffffff811217c3>] ? trace_hardirqs_on+0xd/0xf [ 36.894603] [<ffffffff82eceed0>] ? _raw_spin_unlock_irq+0x31/0x3b [ 36.894606] [<ffffffff81122ca5>] lock_acquire+0x13d/0x1d6 [ 36.894607] [<ffffffff81122ca5>] ? lock_acquire+0x13d/0x1d6 [ 36.894609] [<ffffffff82ecb9d8>] ? __wait_for_common+0x42/0x148 [ 36.894612] [<ffffffff82eced97>] _raw_spin_lock_irq+0x3f/0x75 [ 36.894614] [<ffffffff82ecb9d8>] ? __wait_for_common+0x42/0x148 [ 36.894616] [<ffffffff82ecb9d8>] __wait_for_common+0x42/0x148 [ 36.894618] [<ffffffff82ece3be>] ? usleep_range+0x4b/0x4b [ 36.894620] [<ffffffff82ecbb02>] wait_for_completion+0x24/0x26 [ 36.894626] [<ffffffff810ff577>] kthread_stop+0x107/0x2a2 [ 36.894632] [<ffffffff810f972e>] destroy_workqueue+0x14d/0x201 [ 36.894649] [<ffffffff814fbb84>] xfs_destroy_mount_workqueues+0x19/0x64 [ 36.894652] [<ffffffff814fc687>] xfs_fs_fill_super+0x2b1/0x4cb [ 36.894668] [<ffffffff8121ca45>] mount_bdev+0x144/0x197 [ 36.894671] [<ffffffff814fc3d6>] ? xfs_test_remount_options+0x5d/0x5d [ 36.894673] [<ffffffff814fb11a>] xfs_fs_mount+0x15/0x17 [ 36.894676] [<ffffffff8121d477>] mount_fs+0x67/0x131 [ 36.894682] [<ffffffff81235179>] vfs_kern_mount+0x6b/0xdb [ 36.894687] [<ffffffff81237c67>] do_mount+0x8da/0x9e0 [ 36.894699] [<ffffffff811d4036>] ? strndup_user+0x3f/0x53 [ 36.894702] [<ffffffff81237f8d>] SyS_mount+0x77/0x9f [ 36.894704] [<ffffffff82ecf741>] entry_SYSCALL_64_fastpath+0x1f/0xc2 [ 36.894711] [<ffffffff8111e4d3>] ? trace_hardirqs_off_caller+0x3f/0xab [ 36.894728] BUG: unable to handle kernel NULL pointer dereference at (null) [ 36.894735] IP: [<ffffffff8179b0a8>] __list_add+0x39/0xa1 [ 36.894738] PGD 2a2f6067 PUD 29bb5067 PMD 0 [ 36.894739] Oops: 0000 [#1] SMP [ 36.894742] Modules linked in: [ 36.894744] CPU: 0 PID: 817 Comm: mount Not tainted 4.7.0-rc4-00255-g56c8928 #1 [ 36.894745] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 36.894747] task: ffff880029bf4dc0 ti: ffff880029bf4dc0 task.ti: ffff880029bf4dc0 [ 36.894750] RIP: 0010:[<ffffffff8179b0a8>] [<ffffffff8179b0a8>] __list_add+0x39/0xa1 [ 36.894752] RSP: 0000:ffff8800299a3c50 EFLAGS: 00010046 [ 36.894753] RAX: ffff8800299a3c98 RBX: 0000000000000000 RCX: 0000000000000000 [ 36.894754] RDX: ffff88002a607f18 RSI: 0000000000000000 RDI: ffff8800299a3cb0 [ 36.894755] RBP: ffff8800299a3c68 R08: 0000000000000000 R09: 0000000000000000 [ 36.894756] R10: ffff8800299a3be0 R11: ffff8800299a3652 R12: ffff88002a607f18 [ 36.894758] R13: ffff8800299a3cb0 R14: ffff88002a607ec8 R15: ffff880029bf4dc0 [ 36.894760] FS: 00007fa64919f700(0000) GS:ffff880033600000(0000) knlGS:0000000000000000 [ 36.894761] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 36.894762] CR2: 0000000000000000 CR3: 0000000029b4b000 CR4: 00000000000406f0 [ 36.894766] Stack: [ 36.894770] 7fffffffffffffff ffff88002a607ed0 0000000000000002 ffff8800299a3ce8 [ 36.894772] ffffffff82ecba20 ffff880029d0d580 0000000000000000 ffff8800299a3ce8 [ 36.894775] ffffffff82ece3be 0000000000000001 ffff880029bf4dc0 ffffffff81108749 [ 36.894776] Call Trace: [ 36.894778] [<ffffffff82ecba20>] __wait_for_common+0x8a/0x148 [ 36.894781] [<ffffffff82ece3be>] ? usleep_range+0x4b/0x4b [ 36.894788] [<ffffffff81108749>] ? wake_up_q+0x4c/0x4c [ 36.894790] [<ffffffff82ecbb02>] wait_for_completion+0x24/0x26 [ 36.894792] [<ffffffff810ff577>] kthread_stop+0x107/0x2a2 [ 36.894795] [<ffffffff810f972e>] destroy_workqueue+0x14d/0x201 [ 36.894797] [<ffffffff814fbb84>] xfs_destroy_mount_workqueues+0x19/0x64 [ 36.894800] [<ffffffff814fc687>] xfs_fs_fill_super+0x2b1/0x4cb [ 36.894802] [<ffffffff8121ca45>] mount_bdev+0x144/0x197 [ 36.894805] [<ffffffff814fc3d6>] ? xfs_test_remount_options+0x5d/0x5d [ 36.894807] [<ffffffff814fb11a>] xfs_fs_mount+0x15/0x17 [ 36.894809] [<ffffffff8121d477>] mount_fs+0x67/0x131 [ 36.894812] [<ffffffff81235179>] vfs_kern_mount+0x6b/0xdb [ 36.894814] [<ffffffff81237c67>] do_mount+0x8da/0x9e0 [ 36.894816] [<ffffffff811d4036>] ? strndup_user+0x3f/0x53 [ 36.894819] [<ffffffff81237f8d>] SyS_mount+0x77/0x9f [ 36.894821] [<ffffffff82ecf741>] entry_SYSCALL_64_fastpath+0x1f/0xc2 [ 36.894824] [<ffffffff8111e4d3>] ? trace_hardirqs_off_caller+0x3f/0xab [ 36.894853] Code: 89 fd 48 89 f3 49 89 d4 49 39 f0 74 1e 49 89 d1 48 89 f1 48 c7 c2 64 3a a7 83 be 1d 00 00 00 48 c7 c7 b1 3a a7 83 e8 61 7d 94 ff <4c> 8b 03 4d 39 c4 74 1e 49 89 d9 4c 89 e1 48 c7 c2 d7 3a a7 83 [ 36.894856] RIP [<ffffffff8179b0a8>] __list_add+0x39/0xa1 [ 36.894856] RSP <ffff8800299a3c50> [ 36.894857] CR2: 0000000000000000 [ 36.894865] ---[ end trace 982a86dd6aa6612a ]--- [ 36.894867] Kernel panic - not syncing: Fatal exception FYI, raw QEMU command line is: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -kernel /pkg/linux/x86_64-allyesdebian/gcc-6/56c8928ebabd0c51b34056128ba686e38c867fe1/vmlinuz-4.7.0-rc4-00255-g56c8928 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-kbuild-yocto-x86_64-62/bisect_boot-1-yocto-minimal-x86_64.cgz-x86_64-allyesdebian-56c8928ebabd0c51b34056128ba686e38c867fe1-20160627-93988-zdpc44-0.yaml ARCH=x86_64 kconfig=x86_64-allyesdebian branch=linux-devel/devel-catchup-201606271239 commit=56c8928ebabd0c51b34056128ba686e38c867fe1 BOOT_IMAGE=/pkg/linux/x86_64-allyesdebian/gcc-6/56c8928ebabd0c51b34056128ba686e38c867fe1/vmlinuz-4.7.0-rc4-00255-g56c8928 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-kbuild-yocto-x86_64/yocto-minimal-x86_64.cgz/x86_64-allyesdebian/gcc-6/56c8928ebabd0c51b34056128ba686e38c867fe1/0 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-x86_64-62::dhcp drbd.minor_count=8' -initrd /fs/sdc1/initrd-vm-kbuild-yocto-x86_64-62 -m 832 -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-kbuild-yocto-x86_64-62,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-kbuild-yocto-x86_64-62 -serial file:/dev/shm/kboot/serial-vm-kbuild-yocto-x86_64-62 -daemonize -display none -monitor null Thanks, Kernel Test Robot