rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 2-...!: (1 GPs behind) idle=174c/1/0x4000000000000000 softirq=60342/60343 fqs=4 rcu: (detected by 0, t=10505 jiffies, g=83225, q=447 ncpus=4) Sending NMI from CPU 0 to CPUs 2: NMI backtrace for cpu 2 CPU: 2 UID: 0 PID: 14984 Comm: syz-executor Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:do_raw_spin_lock+0x1c9/0x260 kernel/locking/spinlock_debug.c:119 Code: 00 00 00 00 fc ff df 49 c7 04 04 00 00 00 00 48 8b 44 24 60 65 48 2b 05 fd d1 25 12 0f 85 99 00 00 00 48 83 c4 68 5b 5d 41 5c <41> 5d 41 5e e9 fe ec a5 09 89 44 24 28 89 c6 48 89 df e8 00 b6 a5 RSP: 0000:ffffc90000538e70 EFLAGS: 00000082 RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff81e42d78 RDX: 1ffff1100568509a RSI: 0000000000000004 RDI: ffffc90000538e18 RBP: ffff88802b428600 R08: 0000000000000001 R09: fffff520000a71c3 R10: 0000000000000003 R11: 0000000000000001 R12: ffff8880248cb300 R13: ffff88802b4284d0 R14: 0000000000000002 R15: ffff88802b428650 FS: 0000000000000000(0000) GS:ffff888097380000(0063) knlGS:0000000056578480 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 00000000ffdecdc0 CR3: 0000000059ad8000 CR4: 0000000000352ef0 Call Trace: __run_hrtimer kernel/time/hrtimer.c:1934 [inline] __hrtimer_run_queues+0x1bd/0xa00 kernel/time/hrtimer.c:1994 hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2113 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline] __sysvec_apic_timer_interrupt+0x10b/0x460 arch/x86/kernel/apic/apic.c:1067 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline] sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1061 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:handle_softirqs+0x1ad/0xa00 kernel/softirq.c:608 Code: 30 44 88 74 24 23 45 89 ee 48 c7 c7 00 67 ad 8b e8 a8 2e bf 09 31 d2 65 66 89 15 f6 35 42 12 e8 d9 4e 48 00 fb bb ff ff ff ff <49> c7 c4 c0 a0 40 8e 41 0f bc de 83 c3 01 0f 85 a4 00 00 00 e9 47 RSP: 0000:ffffc90002e6fe58 EFLAGS: 00000206 RAX: 00000000000cd8be RBX: 00000000ffffffff RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff8df19b3c RDI: ffffffff8c1c2380 RBP: 000000010000c2f5 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 000000000000000a R13: 0000000000000004 R14: 0000000000000004 R15: 1ffff920005cdfd3 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0x162/0x210 kernel/softirq.c:735 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline] sysvec_apic_timer_interrupt+0x56/0xc0 arch/x86/kernel/apic/apic.c:1061 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0023:0xf7047aa5 Code: 44 24 28 89 6c 24 30 83 ec 0c 68 10 27 00 00 e8 01 17 13 00 83 c4 0c 68 01 00 00 40 ff 74 24 30 6a ff e8 0e df 12 00 83 c4 10 <39> 44 24 30 0f 84 69 02 00 00 8b bb a4 05 b6 00 8b 83 ac 05 b6 00 RSP: 002b:00000000ffafdbe0 EFLAGS: 00000282 RAX: 0000000000000000 RBX: 00000000f73d4ff4 RCX: 00000000ffafdc48 RDX: 0000000000000000 RSI: 0000000000003a98 RDI: 0000000000000143 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 rcu: rcu_preempt kthread starved for 10485 jiffies! g83225 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 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:28216 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5387 [inline] __schedule+0x10e9/0x6820 kernel/sched/core.c:7188 __schedule_loop kernel/sched/core.c:7267 [inline] schedule+0xdd/0x390 kernel/sched/core.c:7282 schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2095 rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2297 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 rcu: Stack dump where RCU GP kthread last ran: CPU: 0 UID: 0 PID: 18 Comm: rcu_exp_gp_kthr Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline] RIP: 0010:csd_lock kernel/smp.c:357 [inline] RIP: 0010:smp_call_function_single+0x451/0x710 kernel/smp.c:689 Code: 00 fc ff df 48 8b 4c 24 38 48 89 ca 48 c1 ea 03 4c 8d 2c 02 48 89 c8 83 e0 07 44 8d 70 03 e8 d6 4f 0c 00 f3 90 41 0f b6 45 00 <41> 38 c6 7c 08 84 c0 0f 85 23 02 00 00 8b 43 08 31 ff 83 e0 01 41 RSP: 0018:ffffc9000044fb80 EFLAGS: 00000293 RAX: 0000000000000000 RBX: ffff88802b23c680 RCX: ffffffff81fb8810 RDX: ffff88801c370000 RSI: ffffffff81fb87ea RDI: ffff88801c370000 RBP: ffffc9000044fcd0 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: ffff88802b533da0 R12: 0000000000000000 R13: ffffed10056478d1 R14: 0000000000000003 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff888097180000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000f53eaff4 CR3: 000000004e875000 CR4: 0000000000352ef0 Call Trace: __sync_rcu_exp_select_node_cpus+0x4ec/0x9e0 kernel/rcu/tree_exp.h:420 sync_rcu_exp_select_node_cpus kernel/rcu/tree_exp.h:455 [inline] sync_rcu_exp_select_cpus+0x3ca/0xac0 kernel/rcu/tree_exp.h:522 rcu_exp_sel_wait_wake kernel/rcu/tree_exp.h:723 [inline] wait_rcu_exp_gp+0x2c/0x40 kernel/rcu/tree_exp.h:492 kthread_worker_fn+0x2fa/0xc00 kernel/kthread.c:1025 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245