FYI, we noticed the following commit:

https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/vmap_stack
commit 817b8ebf33c489948ee5db93ab7ed483619a53a5 ("sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK")

in testcase: boot

on test machine: 1 threads qemu-system-i386 -enable-kvm with 192M memory

caused below changes:


+-------------------------------------------------------+------------+------------+
|                                                       | 2059c482ae | 817b8ebf33 |
+-------------------------------------------------------+------------+------------+
| boot_successes                                        | 49         | 42         |
| boot_failures                                         | 3          | 8          |
| invoked_oom-killer:gfp_mask=0x                        | 1          | 5          |
| Mem-Info                                              | 1          | 5          |
| Out_of_memory:Kill_process                            | 1          | 5          |
| backtrace:do_execve                                   | 1          | 1          |
| backtrace:SyS_execve                                  | 1          | 1          |
| BUG:unable_to_handle_kernel                           | 2          |            |
| Oops:#[##]                                            | 2          |            |
| EIP_is_at_perf_prepare_sample                         | 2          |            |
| Kernel_panic-not_syncing:Fatal_exception_in_interrupt | 2          |            |
| backtrace:vfs_fstatat                                 | 1          |            |
| backtrace:SyS_fstatat64                               | 1          |            |
| backtrace:do_sys_open                                 | 1          |            |
| backtrace:SyS_open                                    | 1          |            |
| WARNING:at_kernel/fork.c:#free_task                   | 0          | 7          |
| backtrace:_do_fork                                    | 0          | 7          |
| backtrace:SyS_clone                                   | 0          | 7          |
| backtrace:path_listxattr                              | 0          | 1          |
| backtrace:SyS_llistxattr                              | 0          | 1          |
| backtrace:do_writev                                   | 0          | 1          |
| backtrace:SyS_writev                                  | 0          | 1          |
| backtrace:process_vm_rw                               | 0          | 1          |
| backtrace:SyS_process_vm_writev                       | 0          | 1          |
+-------------------------------------------------------+------------+------------+

[   45.554450] ------------[ cut here ]------------
[   45.555623] WARNING: CPU: 0 PID: 2307 at kernel/fork.c:304 free_task+0x2f/0x4c
[   45.557815] CPU: 0 PID: 2307 Comm: trinity-main Not tainted 4.7.0-rc4-00257-g817b8eb #1
[   45.577616] oom_reaper: reaped process 2307 (trinity-main), now anon-rss:0kB, file-rss:0kB, shmem-rss:72kB
[   45.618976] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[   45.621176]  00000000 00000000 c8391e94 c138a35f c8391eb0 c103100c 00000130 c102f285
[   45.624018]  c83e2d40 c7c7ae80 fffffdff c8391ec4 c103108f 00000009 00000000 00000000
[   45.626839]  c8391ed0 c102f285 c83e2d40 c8391f2c c102fb34 00000000 00000000 00000000
[   45.646202] Call Trace:
[   45.667102]  [<c138a35f>] dump_stack+0x16/0x18
[   45.668288]  [<c103100c>] __warn+0xa0/0xb7
[   45.679428]  [<c102f285>] ? free_task+0x2f/0x4c
[   45.680594]  [<c103108f>] warn_slowpath_null+0x11/0x16
[   45.681864]  [<c102f285>] free_task+0x2f/0x4c
[   45.683030]  [<c102fb34>] copy_process+0x476/0x1095
[   45.684442]  [<c10308a8>] _do_fork+0xa1/0x1dc
[   45.685586]  [<c1046882>] ? ___might_sleep+0x2b/0xe6
[   45.686831]  [<c1030a4f>] SyS_clone+0x19/0x1b
[   45.688032]  [<c1000e3c>] do_int80_syscall_32+0x44/0x56
[   45.697264]  [<c1c7f202>] entry_INT80_32+0x2a/0x2a


FYI, raw QEMU command line is:

	qemu-system-i386 -enable-kvm -kernel /pkg/linux/i386-randconfig-b0-07070632/gcc-6/817b8ebf33c489948ee5db93ab7ed483619a53a5/vmlinuz-4.7.0-rc4-00257-g817b8eb -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-intel12-openwrt-i386-15/validate_boot-1-openwrt-i386.cgz-i386-randconfig-b0-07070632-817b8ebf33c489948ee5db93ab7ed483619a53a5-20160707-101992-1a0dh5i-10.yaml ARCH=i386 kconfig=i386-randconfig-b0-07070632 branch=linux-devel/devel-hourly-2016070702 commit=817b8ebf33c489948ee5db93ab7ed483619a53a5 BOOT_IMAGE=/pkg/linux/i386-randconfig-b0-07070632/gcc-6/817b8ebf33c489948ee5db93ab7ed483619a53a5/vmlinuz-4.7.0-rc4-00257-g817b8eb max_uptime=600 RESULT_ROOT=/result/boot/1/vm-intel12-openwrt-i386/openwrt-i386.cgz/i386-randconfig-b0-07070632/gcc-6/817b8ebf33c489948ee5db93ab7ed483619a53a5/10 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-intel12-openwrt-i386-15::dhcp drbd.minor_count=8'  -initrd /fs/KVM/initrd-vm-intel12-openwrt-i386-15 -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/KVM/disk0-vm-intel12-openwrt-i386-15,media=disk,if=virtio -drive file=/fs/KVM/disk1-vm-intel12-openwrt-i386-15,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-intel12-openwrt-i386-15 -serial file:/dev/shm/kboot/serial-vm-intel12-openwrt-i386-15 -daemonize -display none -monitor null 





Thanks,
Xiaolong