FYI, we noticed the following commit (built with gcc-6): commit: b151f93a71fc9fecb560e823a92402d882516483 ("torture: Eliminate torture_runnable") https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2017.11.21a in testcase: boot on test machine: qemu-system-i386 -enable-kvm -smp 2 -m 320M caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +------------------------------------------------+------------+------------+ | | 3d9d746535 | b151f93a71 | +------------------------------------------------+------------+------------+ | boot_successes | 0 | 0 | | boot_failures | 76 | 88 | | genirq:Flags_mismatch_irq##(ttyS0)vs.#(sir_ir) | 76 | 88 | | INFO:rcu_preempt_self-detected_stall_on_CPU | 67 | 38 | | EIP:__do_softirq | 67 | 38 | | EIP:_raw_spin_unlock_irqrestore | 67 | 38 | | INFO:rcu_preempt_detected_stalls_on_CPUs/tasks | 0 | 35 | | EIP:preempt_count_sub | 0 | 1 | | EIP:delay_tsc | 0 | 5 | | EIP:preempt_count_add | 0 | 1 | +------------------------------------------------+------------+------------+ [ 116.310716] INFO: rcu_preempt detected stalls on CPUs/tasks: [ 116.311764] Tasks blocked on level-0 rcu_node (CPUs 0-0): P31 [ 116.312856] (detected by 0, t=10002 jiffies, g=-88, c=-89, q=352) [ 116.314001] rcu_torture_rea R running task 7168 31 2 0x80000000 [ 116.315329] Call Trace: [ 116.315801] __schedule+0x493/0x620 [ 116.316450] ? __softirqentry_text_start+0x8/0x8 [ 116.317306] preempt_schedule_irq+0x4a/0x70 [ 116.318083] resume_kernel+0x27/0x29 [ 116.318753] EIP: preempt_count_sub+0x130/0x140 [ 116.319579] EFLAGS: 00200297 CPU: 0 [ 116.320241] EAX: 47bd1665 EBX: 00000000 ECX: 00000000 EDX: 47bd1665 [ 116.321574] ESI: 7a647087 EDI: 0000000b EBP: 504e7ec4 ESP: 504e7ec4 [ 116.322821] DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068 [ 116.323808] ? delay_tsc+0x65/0xd0 [ 116.324463] ? delay_tsc+0x65/0xd0 [ 116.325095] ? __queue_work+0x300/0x370 [ 116.325810] delay_tsc+0x65/0xd0 [ 116.326440] __delay+0xe/0x10 [ 116.327007] __const_udelay+0x25/0x30 [ 116.327675] rcu_read_delay+0x8a/0x110 [ 116.328414] ? kvm_sched_clock_read+0x8/0x20 [ 116.329242] rcu_torture_reader+0x189/0x320 [ 116.330019] ? rcu_torture_reader+0x320/0x320 [ 116.330833] kthread+0x103/0x110 [ 116.331513] ? rcu_torture_timer_cb+0x10/0x10 [ 116.332331] ? __kthread_create_on_node+0x140/0x140 [ 116.333247] ret_from_fork+0x19/0x24 [ 116.333938] rcu_torture_rea R running task 7168 31 2 0x80000000 [ 116.335236] Call Trace: [ 116.335712] __schedule+0x493/0x620 [ 116.336367] ? __softirqentry_text_start+0x8/0x8 [ 116.337217] preempt_schedule_irq+0x4a/0x70 [ 116.338003] resume_kernel+0x27/0x29 [ 116.338674] EIP: preempt_count_sub+0x130/0x140 [ 116.339490] EFLAGS: 00200297 CPU: 0 [ 116.340162] EAX: 47bd1665 EBX: 00000000 ECX: 00000000 EDX: 47bd1665 [ 116.341300] ESI: 7a647087 EDI: 0000000b EBP: 504e7ec4 ESP: 504e7ec4 [ 116.342470] DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068 [ 116.343449] ? delay_tsc+0x65/0xd0 [ 116.344080] ? delay_tsc+0x65/0xd0 [ 116.344762] ? __queue_work+0x300/0x370 [ 116.345471] delay_tsc+0x65/0xd0 [ 116.346062] __delay+0xe/0x10 [ 116.346642] __const_udelay+0x25/0x30 [ 116.347339] rcu_read_delay+0x8a/0x110 [ 116.348027] ? kvm_sched_clock_read+0x8/0x20 [ 116.348829] rcu_torture_reader+0x189/0x320 [ 116.349621] ? rcu_torture_reader+0x320/0x320 [ 116.350421] kthread+0x103/0x110 [ 116.351038] ? rcu_torture_timer_cb+0x10/0x10 [ 116.351853] ? __kthread_create_on_node+0x140/0x140 [ 116.352742] ret_from_fork+0x19/0x24 [ 116.353432] rcu_preempt kthread starved for 9974 jiffies! g4294967208 c4294967207 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=0 [ 116.355517] rcu_preempt I 7464 8 2 0x80000000 [ 116.356543] Call Trace: [ 116.357008] __schedule+0x493/0x620 [ 116.357682] schedule+0x24/0x40 [ 116.358291] schedule_timeout+0x330/0x3b0 [ 116.359024] ? preempt_count_sub+0xea/0x140 [ 116.359806] ? collect_expired_timers+0xb0/0xb0 [ 116.360660] rcu_gp_kthread+0x6bf/0xef0 [ 116.361364] ? _raw_spin_unlock_irq+0x32/0x50 [ 116.362178] ? __schedule+0x4cd/0x620 [ 116.362874] kthread+0x103/0x110 [ 116.363476] ? rcu_implicit_dynticks_qs+0x3b0/0x3b0 [ 116.364377] ? __kthread_create_on_node+0x140/0x140 [ 116.365290] ret_from_fork+0x19/0x24 [ 116.367322] sir_ir sir_ir.0: Trapped in interrupt [ 116.369468] sir_ir sir_ir.0: Trapped in interrupt [ 116.371646] sir_ir sir_ir.0: Trapped in interrupt [ 116.373797] sir_ir sir_ir.0: Trapped in interrupt [ 116.375953] sir_ir sir_ir.0: Trapped in interrupt [ 116.378112] sir_ir sir_ir.0: Trapped in interrupt [ 116.380277] sir_ir sir_ir.0: Trapped in interrupt [ 116.382452] sir_ir sir_ir.0: Trapped in interrupt [ 116.384602] sir_ir sir_ir.0: Trapped in interrupt [ 116.386762] sir_ir sir_ir.0: Trapped in interrupt [ 116.388917] sir_ir sir_ir.0: Trapped in interrupt [ 116.391059] sir_ir sir_ir.0: Trapped in interrupt [ 116.393248] sir_ir sir_ir.0: Trapped in interrupt [ 116.395407] sir_ir sir_ir.0: Trapped in interrupt [ 116.397562] sir_ir sir_ir.0: Trapped in interrupt [ 116.399723] sir_ir sir_ir.0: Trapped in interrupt [ 116.401899] sir_ir sir_ir.0: Trapped in interrupt [ 116.404055] sir_ir sir_ir.0: Trapped in interrupt [ 116.406212] sir_ir sir_ir.0: Trapped in interrupt [ 116.408371] sir_ir sir_ir.0: Trapped in interrupt [ 116.410528] sir_ir sir_ir.0: Trapped in interrupt [ 116.412710] sir_ir sir_ir.0: Trapped in interrupt [ 116.414859] sir_ir sir_ir.0: Trapped in interrupt [ 116.417008] sir_ir sir_ir.0: Trapped in interrupt [ 116.419165] sir_ir sir_ir.0: Trapped in interrupt [ 116.421342] sir_ir sir_ir.0: Trapped in interrupt [ 116.424341] sir_ir sir_ir.0: Trapped in interrupt [ 116.426505] sir_ir sir_ir.0: Trapped in interrupt [ 116.428662] sir_ir sir_ir.0: Trapped in interrupt [ 116.430817] sir_ir sir_ir.0: Trapped in interrupt [ 116.432982] sir_ir sir_ir.0: Trapped in interrupt [ 116.435134] sir_ir sir_ir.0: Trapped in interrupt [ 116.437290] sir_ir sir_ir.0: Trapped in interrupt To reproduce: git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k job-script # job-script is attached in this email Thanks, Xiaolong