FYI, we noticed the following commit (built with gcc-7): commit: 0b4f83d510f6fef6bb9da25f122c8d733d50516f ("[PATCH 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()") url: https://github.com/0day-ci/linux/commits/Dmitry-Safonov/tty-Hold-write-ld... base: https://git.kernel.org/cgit/linux/kernel/git/gregkh/tty.git tty-testing in testcase: trinity with following parameters: runtime: 300s test-description: Trinity is a linux system call fuzz tester. test-url: http://codemonkey.org.uk/projects/trinity/ on test machine: qemu-system-x86_64 -enable-kvm -m 256M caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +--------------------------------------------------+------------+------------+ | | 58dd163974 | 0b4f83d510 | +--------------------------------------------------+------------+------------+ | boot_successes | 14 | 4 | | boot_failures | 0 | 6 | | INFO:task_blocked_for_more_than#seconds | 0 | 6 | | Kernel_panic-not_syncing:hung_task:blocked_tasks | 0 | 6 | +--------------------------------------------------+------------+------------+ [ 244.816801] INFO: task validate_data:655 blocked for more than 120 seconds. [ 244.818833] Not tainted 4.18.0-11684-g0b4f83d #1 [ 244.820028] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 244.826965] validate_data D 0 655 623 0x20020000 [ 244.828279] Call Trace: [ 244.828958] ? __schedule+0x843/0x950 [ 244.830173] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.834903] schedule+0x31/0x70 [ 244.835665] schedule_timeout+0x34/0x760 [ 244.836613] ? ftrace_likely_update+0x35/0x60 [ 244.837683] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.838818] ? ftrace_likely_update+0x35/0x60 [ 244.840127] ? ftrace_likely_update+0x35/0x60 [ 244.845947] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.847882] __ldsem_down_read_nested+0x23a/0x3b0 [ 244.849886] ? tty_ldisc_ref_wait+0x25/0x50 [ 244.853807] tty_ldisc_ref_wait+0x25/0x50 [ 244.854946] tty_compat_ioctl+0x8a/0x120 [ 244.855928] ? this_tty+0x80/0x80 [ 244.856742] __ia32_compat_sys_ioctl+0xc28/0x1ce0 [ 244.857981] do_int80_syscall_32+0x1d2/0x5f0 [ 244.859003] entry_INT80_compat+0x88/0xa0 [ 244.859972] INFO: task dnsmasq:668 blocked for more than 120 seconds. [ 244.868315] Not tainted 4.18.0-11684-g0b4f83d #1 [ 244.869583] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 244.871744] dnsmasq D 0 668 1 0x20020000 [ 244.873063] Call Trace: [ 244.873697] ? __schedule+0x843/0x950 [ 244.874572] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.875725] schedule+0x31/0x70 [ 244.876576] schedule_timeout+0x34/0x760 [ 244.877573] ? ftrace_likely_update+0x35/0x60 [ 244.878660] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.879872] ? ftrace_likely_update+0x35/0x60 [ 244.890522] ? ftrace_likely_update+0x35/0x60 [ 244.891572] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.892746] __ldsem_down_read_nested+0x23a/0x3b0 [ 244.893861] ? tty_ldisc_ref_wait+0x25/0x50 [ 244.894841] tty_ldisc_ref_wait+0x25/0x50 [ 244.895911] tty_compat_ioctl+0x8a/0x120 [ 244.896916] ? this_tty+0x80/0x80 [ 244.897717] __ia32_compat_sys_ioctl+0xc28/0x1ce0 [ 244.898821] do_int80_syscall_32+0x1d2/0x5f0 [ 244.899830] entry_INT80_compat+0x88/0xa0 [ 244.909466] INFO: task dropbear:734 blocked for more than 120 seconds. [ 244.911173] Not tainted 4.18.0-11684-g0b4f83d #1 [ 244.912394] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 244.914176] dropbear D 0 734 1 0x20020000 [ 244.915446] Call Trace: [ 244.916068] ? __schedule+0x843/0x950 [ 244.916945] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.918076] schedule+0x31/0x70 [ 244.918832] schedule_timeout+0x34/0x760 [ 244.919781] ? ftrace_likely_update+0x35/0x60 [ 244.921104] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.922304] ? ftrace_likely_update+0x35/0x60 [ 244.923347] ? ftrace_likely_update+0x35/0x60 [ 244.924369] ? __ldsem_down_read_nested+0x1c4/0x3b0 [ 244.925496] __ldsem_down_read_nested+0x23a/0x3b0 [ 244.926598] ? tty_ldisc_ref_wait+0x25/0x50 [ 244.927578] tty_ldisc_ref_wait+0x25/0x50 [ 244.928526] tty_compat_ioctl+0x8a/0x120 [ 244.929449] ? this_tty+0x80/0x80 [ 244.930240] __ia32_compat_sys_ioctl+0xc28/0x1ce0 [ 244.940083] do_int80_syscall_32+0x1d2/0x5f0 [ 244.941310] entry_INT80_compat+0x88/0xa0 [ 244.944070] [ 244.944070] Showing all locks held in the system: [ 244.945558] 1 lock held by khungtaskd/18: [ 244.946495] #0: (____ptrval____) (rcu_read_lock){....}, at: debug_show_all_locks+0x16/0x190 [ 244.948503] 2 locks held by askfirst/235: [ 244.949439] #0: (____ptrval____) (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x50 [ 244.951762] #1: (____ptrval____) (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x13d/0xa00 [ 244.953799] 1 lock held by validate_data/655: [ 244.954814] #0: (____ptrval____) (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x50 [ 244.956764] 1 lock held by dnsmasq/668: [ 244.957649] #0: (____ptrval____) (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x50 [ 244.959598] 1 lock held by dropbear/734: [ 244.967564] #0: (____ptrval____) (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x50 [ 244.969581] [ 244.969975] ============================================= [ 244.969975] [ 244.971833] NMI backtrace for cpu 0 [ 244.972696] CPU: 0 PID: 18 Comm: khungtaskd Not tainted 4.18.0-11684-g0b4f83d #1 [ 244.974371] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 244.976260] Call Trace: [ 244.976895] dump_stack+0xb9/0x10e [ 244.977723] ? lapic_can_unplug_cpu+0xa0/0xa0 [ 244.978735] nmi_cpu_backtrace+0x13a/0x150 [ 244.979697] ? lapic_can_unplug_cpu+0xa0/0xa0 [ 244.980713] nmi_trigger_cpumask_backtrace+0x188/0x280 [ 244.981899] watchdog+0x83b/0x880 [ 244.982683] ? reset_hung_task_detector+0x20/0x20 [ 244.983762] kthread+0x170/0x180 [ 244.984509] ? kthread_create_worker_on_cpu+0x70/0x70 [ 244.985659] ret_from_fork+0x24/0x30 [ 244.990807] Kernel panic - not syncing: hung_task: blocked tasks [ 244.992205] CPU: 0 PID: 18 Comm: khungtaskd Not tainted 4.18.0-11684-g0b4f83d #1 [ 244.993881] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 244.995769] Call Trace: [ 244.996362] dump_stack+0xb9/0x10e [ 244.997166] panic+0xfd/0x2bb [ 244.997878] ? nmi_trigger_cpumask_backtrace+0x269/0x280 [ 244.999097] ? watchdog+0x83b/0x880 [ 244.999982] watchdog+0x847/0x880 [ 245.000782] ? reset_hung_task_detector+0x20/0x20 [ 245.001862] kthread+0x170/0x180 [ 245.002613] ? kthread_create_worker_on_cpu+0x70/0x70 [ 245.003785] ret_from_fork+0x24/0x30 [ 245.004646] Kernel Offset: 0x10800000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 245.007065] Rebooting in 3 seconds.. Elapsed time: 250 #!/bin/bash # To reproduce, # 1) save job-script and this script (both are attached in 0day report email) # 2) run this script with your compiled kernel and optional env $INSTALL_MOD_PATH kernel=$1 initrds=( /osimage/openwrt/openwrt-i386-2016-03-16.cgz /lkp/lkp/lkp-i386.cgz /osimage/pkg/debian-x86_64-2016-08-31.cgz/trinity-static-i386-x86_64-6ddabfd2_2017-11-10.cgz ) HTTP_PREFIX=https://download.01.org/0day-ci/lkp-qemu wget --timestamping "${initrds[@]/#/$HTTP_PREFIX}" { cat "${initrds[@]//*\//}" [[ $INSTALL_MOD_PATH ]] && ( cd "$INSTALL_MOD_PATH" find lib | cpio -o -H newc --quiet | gzip ) echo job-script | cpio -o -H newc --quiet | gzip } > initrd.img qemu-img create -f qcow2 disk-vm-lkp-hsw-4ep1-openwrt-ia32-13-0 256G qemu-img create -f qcow2 disk-vm-lkp-hsw-4ep1-openwrt-ia32-13-1 256G kvm=( qemu-system-x86_64 To reproduce: git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email Thanks, Rong, Chen