Greeting, FYI, we noticed the following commit (built with gcc-11): commit: 0494d3eb4bb52f12bae92e54c714df2b37305626 ("sched,ptrace: Fix ptrace_check_attach() vs PREEMPT_RT") https://git.kernel.org/cgit/linux/kernel/git/peterz/queue.git sched/wip.freezer in testcase: boot on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +--------------------------------------------------+------------+------------+ | | 7dc1bdf5f1 | 0494d3eb4b | +--------------------------------------------------+------------+------------+ | INFO:rcu_sched_self-detected_stall_on_CPU | 0 | 54 | | EIP:_raw_spin_unlock_irqrestore | 0 | 50 | | BUG:workqueue_lockup-pool | 0 | 42 | +--------------------------------------------------+------------+------------+ If you fix the issue, kindly add following tag Reported-by: kernel test robot [ 62.996971][ C0] BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 55s! [ 62.998858][ C0] Showing busy workqueues and worker pools: [ 63.000041][ C0] workqueue events: flags=0x0 [ 63.001074][ C0] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 refcnt=3 [ 63.001082][ C0] pending: release_one_tty, release_one_tty [ 63.001091][ C0] workqueue events_power_efficient: flags=0x80 [ 63.005005][ C0] pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256 refcnt=2 [ 63.005013][ C0] pending: do_cache_clean [ 63.005020][ C0] workqueue mm_percpu_wq: flags=0x8 [ 63.008694][ C0] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 refcnt=4 [ 63.008703][ C0] pending: lru_add_drain_per_cpu BAR(30), vmstat_update [ 63.008720][ C0] workqueue mld: flags=0x40008 [ 63.012969][ C0] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 refcnt=2 [ 63.012978][ C0] pending: mld_dad_work [ 93.716958][ C0] BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 86s! [ 93.718659][ C0] Showing busy workqueues and worker pools: [ 93.719675][ C0] workqueue events: flags=0x0 [ 93.720525][ C0] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 refcnt=3 [ 93.720532][ C0] pending: release_one_tty, release_one_tty [ 93.720541][ C0] workqueue events_power_efficient: flags=0x80 [ 93.724167][ C0] pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256 refcnt=2 [ 93.724173][ C0] pending: do_cache_clean [ 93.724180][ C0] workqueue mm_percpu_wq: flags=0x8 [ 93.727411][ C0] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 refcnt=4 [ 93.727417][ C0] pending: lru_add_drain_per_cpu BAR(30), vmstat_update [ 93.727431][ C0] workqueue mld: flags=0x40008 [ 93.730941][ C0] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 refcnt=2 [ 93.730947][ C0] pending: mld_dad_work [ 107.652927][ C1] rcu: INFO: rcu_sched self-detected stall on CPU [ 107.654368][ C1] rcu: 1-....: (24967 ticks this GP) idle=617/1/0x40000000 softirq=2264/2266 fqs=12390 [ 107.656312][ C1] (t=25001 jiffies g=-555 q=10932) [ 107.657436][ C1] NMI backtrace for cpu 1 [ 107.658320][ C1] CPU: 1 PID: 1 Comm: init Not tainted 5.18.0-rc2-00235-g0494d3eb4bb5 #1 [ 107.659993][ C1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 [ 107.661709][ C1] Call Trace: [ 107.662288][ C1] ? show_stack+0x3d/0x45 [ 107.663004][ C1] dump_stack_lvl+0x34/0x44 [ 107.663741][ C1] dump_stack+0xd/0x10 [ 107.664418][ C1] nmi_cpu_backtrace.cold+0x16/0x66 [ 107.665263][ C1] ? lapic_can_unplug_cpu+0x80/0x80 [ 107.666092][ C1] nmi_trigger_cpumask_backtrace+0x9f/0xc0 [ 107.667007][ C1] arch_trigger_cpumask_backtrace+0x15/0x40 [ 107.667934][ C1] trigger_single_cpu_backtrace+0x1b/0x1f [ 107.668835][ C1] rcu_dump_cpu_stacks+0x8b/0xc2 [ 107.669650][ C1] print_cpu_stall.cold+0x3f/0x145 [ 107.670461][ C1] check_cpu_stall+0xd5/0x240 [ 107.671217][ C1] rcu_sched_clock_irq+0xb9/0x280 [ 107.672023][ C1] update_process_times+0x77/0xc0 [ 107.672825][ C1] tick_sched_handle+0x28/0x80 [ 107.673824][ C1] tick_sched_timer+0x7a/0xc0 [ 107.674851][ C1] __hrtimer_run_queues+0x13a/0x280 [ 107.675984][ C1] ? tick_sched_do_timer+0xc0/0xc0 [ 107.677043][ C1] hrtimer_interrupt+0x113/0x280 [ 107.677842][ C1] ? sysvec_call_function_single+0x40/0x40 [ 107.678748][ C1] __sysvec_apic_timer_interrupt+0x55/0x100 [ 107.679666][ C1] sysvec_apic_timer_interrupt+0x22/0x40 [ 107.680553][ C1] handle_exception+0x133/0x133 [ 107.681353][ C1] EIP: __ia32_sys_ptrace+0x29f/0x340 [ 107.682195][ C1] Code: 01 00 00 e9 73 ff ff ff 8d 76 00 be ff ff ff ff e9 0e ff ff ff bf 02 00 00 00 90 8d 4d e4 ba c0 e5 07 c7 89 d8 e8 a1 f3 02 00 <89> c6 83 f8 f5 74 29 83 f8 fd 0f 84 41 fe ff ff 83 f8 8d 75 dc eb [ 107.685098][ C1] EAX: 00000000 EBX: c1ba0000 ECX: 00000246 EDX: 00000246 [ 107.686185][ C1] ESI: 00000000 EDI: 00000002 EBP: c1139f84 ESP: c1139f5c [ 107.687261][ C1] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 EFLAGS: 00000286 [ 107.688473][ C1] ? copy_process+0x13bb/0x1400 [ 107.689269][ C1] ? sysvec_call_function_single+0x40/0x40 [ 107.690203][ C1] ? sysvec_call_function_single+0x40/0x40 [ 107.691107][ C1] ? __ia32_sys_ptrace+0x29f/0x340 [ 107.691923][ C1] __do_fast_syscall_32+0x5b/0x100 [ 107.692735][ C1] do_fast_syscall_32+0x29/0x80 [ 107.693530][ C1] do_SYSENTER_32+0x15/0x40 [ 107.694259][ C1] entry_SYSENTER_32+0x98/0xf1 [ 107.695027][ C1] EIP: 0xb7f6b589 [ 107.695660][ C1] Code: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d 76 00 58 b8 77 00 00 00 cd 80 90 8d 76 [ 107.698569][ C1] EAX: ffffffda EBX: 00004200 ECX: 00000057 EDX: 00000000 [ 107.699653][ C1] ESI: 00000012 EDI: b7ee8ff4 EBP: bfbff0f8 ESP: bfbff090 [ 107.700733][ C1] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000202 To reproduce: # build kernel cd linux cp config-5.18.0-rc2-00235-g0494d3eb4bb5 .config make HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 olddefconfig prepare modules_prepare bzImage modules make HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 INSTALL_MOD_PATH= modules_install cd find lib/ | cpio -o -H newc --quiet | gzip > modules.cgz git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k -m modules.cgz job-script # job-script is attached in this email # if come across any failure that blocks the test, # please remove ~/.lkp and /lkp dir to run from a clean state. -- 0-DAY CI Kernel Test Service https://01.org/lkp