rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: (detected by 1, t=10502 jiffies, g=3729, q=260) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294951951-4294941448), jiffies_till_next_fqs=1, root ->qsmask 0x0 rcu: rcu_preempt kthread starved for 10505 jiffies! g3729 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:14248 pid: 12 ppid: 2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:4327 [inline] __schedule+0x420/0x900 kernel/sched/core.c:5078 schedule+0x3e/0xf0 kernel/sched/core.c:5157 schedule_timeout+0x1bd/0x2e0 kernel/time/timer.c:1878 rcu_gp_fqs_loop kernel/rcu/tree.c:1940 [inline] rcu_gp_kthread+0x753/0xcd0 kernel/rcu/tree.c:2113 kthread+0x15a/0x180 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 ================================ WARNING: inconsistent lock state 5.11.0-rc5-syzkaller #0 Not tainted -------------------------------- inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage. syz-executor.2/6947 [HC0[0]:SC1[1]:HE0:SE0] takes: ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: rcu_sched_clock_irq.cold.96+0x119/0x64b kernel/rcu/tree.c:2580 {IN-HARDIRQ-W} state was registered at: lock_acquire+0xf9/0x410 kernel/locking/lockdep.c:5442 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x5d/0x80 kernel/locking/spinlock.c:159 rcu_exp_handler+0xa1/0xf0 kernel/rcu/tree_exp.h:678 flush_smp_call_function_queue+0xe2/0x1d0 kernel/smp.c:425 generic_smp_call_function_single_interrupt+0xe/0x10 kernel/smp.c:316 __sysvec_call_function_single+0x45/0x1f0 arch/x86/kernel/smp.c:248 asm_call_irq_on_stack+0xf/0x20 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline] run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline] sysvec_call_function_single+0xd5/0xf0 arch/x86/kernel/smp.c:243 asm_sysvec_call_function_single+0x12/0x20 arch/x86/include/asm/idtentry.h:637 arch_local_irq_restore arch/x86/include/asm/paravirt.h:653 [inline] seqcount_lockdep_reader_access include/linux/seqlock.h:105 [inline] set_root+0xb1/0x1c0 fs/namei.c:852 nd_jump_root+0xb0/0xe0 fs/namei.c:873 path_init+0x4e3/0x650 fs/namei.c:2246 path_openat+0x7e/0xa90 fs/namei.c:3366 do_filp_open+0x8e/0x100 fs/namei.c:3398 do_open_execat+0x73/0x1b0 fs/exec.c:913 bprm_execve+0x17e/0x830 fs/exec.c:1801 kernel_execve+0x13f/0x1c0 fs/exec.c:1969 call_usermodehelper_exec_async+0xc7/0x130 kernel/umh.c:110 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 irq event stamp: 152044159 hardirqs last enabled at (152044157): [] irqentry_exit+0x6c/0xa0 kernel/entry/common.c:403 hardirqs last disabled at (152044158): [] irqentry_enter+0x49/0x50 kernel/entry/common.c:327 softirqs last enabled at (152044154): [] copy_init_fpstate_to_fpregs arch/x86/kernel/fpu/core.c:352 [inline] softirqs last enabled at (152044154): [] fpu__clear+0xa9/0x110 arch/x86/kernel/fpu/core.c:379 softirqs last disabled at (152044159): [] asm_call_irq_on_stack+0xf/0x20 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(rcu_node_0); lock(rcu_node_0); *** DEADLOCK *** 1 lock held by syz-executor.2/6947: #0: ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: print_other_cpu_stall kernel/rcu/tree_stall.h:493 [inline] #0: ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: check_cpu_stall kernel/rcu/tree_stall.h:652 [inline] #0: ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: rcu_pending kernel/rcu/tree.c:3751 [inline] #0: ffffffff843c6e18 (rcu_node_0){?.-.}-{2:2}, at: rcu_sched_clock_irq.cold.96+0x119/0x64b kernel/rcu/tree.c:2580 stack backtrace: CPU: 1 PID: 6947 Comm: syz-executor.2 Not tainted 5.11.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0xa9/0xd1 lib/dump_stack.c:120 print_usage_bug.cold.72+0x195/0x19e kernel/locking/lockdep.c:3740 valid_state kernel/locking/lockdep.c:3751 [inline] mark_lock_irq kernel/locking/lockdep.c:3954 [inline] mark_lock.part.49+0x500/0x550 kernel/locking/lockdep.c:4411 mark_lock kernel/locking/lockdep.c:4375 [inline] mark_held_locks+0x4e/0x80 kernel/locking/lockdep.c:4012 __trace_hardirqs_on_caller kernel/locking/lockdep.c:4030 [inline] lockdep_hardirqs_on_prepare+0x84/0x1d0 kernel/locking/lockdep.c:4098 trace_hardirqs_on+0x20/0x100 kernel/trace/trace_preemptirq.c:49 __do_softirq+0xb2/0x528 kernel/softirq.c:327 asm_call_irq_on_stack+0xf/0x20 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline] do_softirq_own_stack+0x82/0xa0 arch/x86/kernel/irq_64.c:77 invoke_softirq kernel/softirq.c:226 [inline] __irq_exit_rcu kernel/softirq.c:420 [inline] irq_exit_rcu+0xf1/0x120 kernel/softirq.c:432 sysvec_apic_timer_interrupt+0x5d/0xf0 arch/x86/kernel/apic/apic.c:1096 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:629 RIP: 0033:0x402b00 Code: 01 49 83 c5 09 45 39 67 1c 7f ce 48 69 db e8 04 00 00 44 89 b3 04 05 a7 00 48 83 c4 08 5b 5d 41 5c 41 5d 41 5e 41 5f c3 66 90 <53> 48 8b 76 10 89 fb 64 8b 04 25 d0 ff ff ff 85 c0 74 3d 48 8d 86 RSP: 002b:00007f90a58634b8 EFLAGS: 00000206 RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000414717 RDX: 00007f90a58634c0 RSI: 00007f90a58635f0 RDI: 000000000000000b RBP: 000000000075bf20 R08: 00007f90a5863a70 R09: 000000000075bf20 R10: 0000000000000000 R11: 0000000000000000 R12: 00007f90a58646d4 R13: 00000000004caed8 R14: 00000000004e44f8 R15: 00000000ffffffff