FYI, we noticed the following commit: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/vmap_stack commit ec58e505925c46bd43f9c4275c78292d4483af16 ("sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") in testcase: trinity with following parameters: runtime=300s on test machine: vm-kbuild-2G: 2 threads qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap with 2G memory caused below changes: +-------------------------------------+------------+------------+ | | ddf4847e6f | ec58e50592 | +-------------------------------------+------------+------------+ | boot_successes | 8 | 4 | | boot_failures | 0 | 4 | | WARNING:at_kernel/fork.c:#free_task | 0 | 4 | | backtrace:_do_fork | 0 | 4 | | backtrace:SyS_clone | 0 | 4 | +-------------------------------------+------------+------------+ [ 29.950472] sock: process `trinity-main' is using obsolete setsockopt SO_BSDCOMPAT [ 39.309659] VFS: Warning: trinity-c0 using old stat() call. Recompile your binary. [ 40.512647] ------------[ cut here ]------------ [ 40.514588] WARNING: CPU: 0 PID: 5132 at kernel/fork.c:296 free_task+0x35/0x5f [ 40.523082] Modules linked in: acpi_cpufreq [ 40.525310] CPU: 0 PID: 5132 Comm: trinity-c0 Not tainted 4.7.0-rc4-00255-gec58e50 #1 [ 40.530022] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 40.546800] 0000000000000000 ffff88007e90fd50 ffffffff814e4776 0000000000000000 [ 40.559103] 0000000000000000 ffff88007e90fd90 ffffffff8110267c 000001287e90fda0 [ 40.572406] ffff88007e84d280 ffff8800751b2800 00000000fffffff4 ffff88007e42f0b8 [ 40.584404] Call Trace: [ 40.586590] [<ffffffff814e4776>] dump_stack+0x85/0xbe [ 40.588487] [<ffffffff8110267c>] __warn+0xca/0xe5 [ 40.600659] [<ffffffff81102753>] warn_slowpath_null+0x1d/0x1f [ 40.607024] [<ffffffff810ffcc8>] free_task+0x35/0x5f [ 40.610301] [<ffffffff81100a03>] copy_process+0x710/0x1717 [ 40.612306] [<ffffffff81101bb6>] _do_fork+0xbe/0x358 [ 40.623198] [<ffffffff81101ed6>] SyS_clone+0x19/0x1b [ 40.628181] [<ffffffff810019c6>] do_syscall_64+0x69/0xc6 [ 40.634729] [<ffffffff81a9ae44>] entry_SYSCALL64_slow_path+0x25/0x25 [ 40.650469] ---[ end trace 942898900a0dd524 ]--- [ 222.049702] random: nonblocking pool is initialized FYI, raw QEMU command line is: qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap -kernel /pkg/linux/x86_64-lkp/gcc-4.9/ec58e505925c46bd43f9c4275c78292d4483af16/vmlinuz-4.7.0-rc4-00255-gec58e50 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-kbuild-2G-11/bisect_trinity-300s-debian-x86_64-2015-02-07.cgz-x86_64-lkp-ec58e505925c46bd43f9c4275c78292d4483af16-20160627-111363-1oj47zp-0.yaml ARCH=x86_64 kconfig=x86_64-lkp branch=luto/x86/vmap_stack commit=ec58e505925c46bd43f9c4275c78292d4483af16 BOOT_IMAGE=/pkg/linux/x86_64-lkp/gcc-4.9/ec58e505925c46bd43f9c4275c78292d4483af16/vmlinuz-4.7.0-rc4-00255-gec58e50 max_uptime=1500 RESULT_ROOT=/result/trinity/300s/vm-kbuild-2G/debian-x86_64-2015-02-07.cgz/x86_64-lkp/gcc-4.9/ec58e505925c46bd43f9c4275c78292d4483af16/0 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-2G-11::dhcp' -initrd /fs/sdd1/initrd-vm-kbuild-2G-11 -m 2048 -smp 2 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::23026-:22 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -drive file=/fs/sdd1/disk0-vm-kbuild-2G-11,media=disk,if=virtio -drive file=/fs/sdd1/disk1-vm-kbuild-2G-11,media=disk,if=virtio -drive file=/fs/sdd1/disk2-vm-kbuild-2G-11,media=disk,if=virtio -drive file=/fs/sdd1/disk3-vm-kbuild-2G-11,media=disk,if=virtio -drive file=/fs/sdd1/disk4-vm-kbuild-2G-11,media=disk,if=virtio -drive file=/fs/sdd1/disk5-vm-kbuild-2G-11,media=disk,if=virtio -drive file=/fs/sdd1/disk6-vm-kbuild-2G-11,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-kbuild-2G-11 -serial file:/dev/shm/kboot/serial-vm-kbuild-2G-11 -daemonize -display none -monitor null To reproduce: git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git cd lkp-tests bin/lkp install job.yaml # job file is attached in this email bin/lkp run job.yaml Thanks, Xiaolong