rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 1-...!: (1 GPs behind) idle=c55c/1/0x4000000000000000 softirq=64674/64675 fqs=0 rcu: (detected by 0, t=10502 jiffies, g=48921, q=26 ncpus=2) Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 16149 Comm: syz.5.2117 Not tainted 6.15.0-rc4-syzkaller-00052-g4f79eaa2ceac #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 RIP: 0010:__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline] RIP: 0010:_raw_spin_lock_irq+0x9d/0xf0 kernel/locking/spinlock.c:170 Code: 02 00 00 74 05 e8 f3 f5 75 f6 bf 01 00 00 00 e8 a9 74 3f f6 48 8d 7b 18 31 f6 31 d2 31 c9 41 b8 01 00 00 00 45 31 c9 ff 75 08 be c3 4c f6 48 83 c4 08 48 89 df e8 e2 67 4d f6 48 c7 04 24 0e RSP: 0018:ffffc90000a08c98 EFLAGS: 00000046 RAX: 0000000000010001 RBX: ffff8880b89276c0 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880b89276d8 RBP: ffffc90000a08d30 R08: 0000000000000001 R09: 0000000000000000 R10: dffffc0000000000 R11: fffffbfff1efb54f R12: ffff8880226dd340 R13: dffffc0000000000 R14: 1ffff92000141194 R15: dffffc0000000000 FS: 00007fc4c82496c0(0000) GS:ffff888126200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fcbdd1b7bac CR3: 0000000030f8e000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __run_hrtimer kernel/time/hrtimer.c:1765 [inline] __hrtimer_run_queues+0x602/0xc60 kernel/time/hrtimer.c:1825 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1887 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline] __sysvec_apic_timer_interrupt+0x108/0x410 arch/x86/kernel/apic/apic.c:1055 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline] sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1049 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:lock_is_held_type+0x5/0x190 kernel/locking/lockdep.c:5923 Code: 0b 90 90 90 eb b5 e8 1a fc ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 10 65 48 8b 05 a6 35 23 07 48 RSP: 0018:ffffc900044af8d0 EFLAGS: 00000202 RAX: 0000000000000001 RBX: 1ffff92000895f24 RCX: ffff888042a35a00 RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffffffff8df3b8c0 RBP: ffffc900044af9f8 R08: ffffc900044afaf7 R09: 0000000000000000 R10: ffffc900044afac0 R11: fffff52000895f5f R12: dffffc0000000000 R13: dffffc0000000000 R14: ffffffff8bc0b120 R15: 0000000000000000 lock_is_held include/linux/lockdep.h:249 [inline] __might_resched+0xa6/0x610 kernel/sched/core.c:8780 __might_fault+0x77/0x130 mm/memory.c:7149 _inline_copy_from_user include/linux/uaccess.h:162 [inline] _copy_from_user+0x28/0xb0 lib/usercopy.c:18 copy_from_user include/linux/uaccess.h:212 [inline] copy_msghdr_from_user net/socket.c:2496 [inline] recvmsg_copy_msghdr net/socket.c:2752 [inline] ___sys_recvmsg+0x12e/0x510 net/socket.c:2824 do_recvmmsg+0x307/0x760 net/socket.c:2923 __sys_recvmmsg net/socket.c:2997 [inline] __do_sys_recvmmsg net/socket.c:3020 [inline] __se_sys_recvmmsg net/socket.c:3013 [inline] __x64_sys_recvmmsg+0x190/0x240 net/socket.c:3013 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fc4c738e969 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc4c8249038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007fc4c75b6080 RCX: 00007fc4c738e969 RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003 RBP: 00007fc4c7410ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007fc4c75b6080 R15: 00007ffc53776238 rcu: rcu_preempt kthread starved for 10502 jiffies! g48921 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:27304 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5382 [inline] __schedule+0x168f/0x4c70 kernel/sched/core.c:6767 __schedule_loop kernel/sched/core.c:6845 [inline] schedule+0x165/0x360 kernel/sched/core.c:6860 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2046 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2248 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153 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: 16170 Comm: syz.6.2125 Not tainted 6.15.0-rc4-syzkaller-00052-g4f79eaa2ceac #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 RIP: 0010:csd_lock_wait kernel/smp.c:340 [inline] RIP: 0010:smp_call_function_many_cond+0xe69/0x11c0 kernel/smp.c:885 Code: 00 45 8b 2f 44 89 ee 83 e6 01 31 ff e8 10 6d 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 bb 68 0b 00 eb 37 f3 90 <43> 0f b6 04 2c 84 c0 75 10 41 f7 07 01 00 00 00 74 1e e8 a0 68 0b RSP: 0018:ffffc9000430f4e0 EFLAGS: 00000293 RAX: ffffffff81b456c0 RBX: ffff8880b883abc0 RCX: ffff8880526d1e00 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffc9000430f640 R08: ffffffff8f7daa77 R09: 1ffffffff1efb54e R10: dffffc0000000000 R11: fffffbfff1efb54f R12: 1ffff11017127e69 R13: dffffc0000000000 R14: 0000000000000001 R15: ffff8880b893f348 FS: 0000000000000000(0000) GS:ffff888126100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c313fd8 CR3: 000000002a6de000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1052 __flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline] flush_tlb_multi arch/x86/mm/tlb.c:1275 [inline] flush_tlb_mm_range+0x6ae/0x12b0 arch/x86/mm/tlb.c:1365 tlb_flush arch/x86/include/asm/tlb.h:23 [inline] tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:480 [inline] tlb_flush_mmu+0x1a7/0x680 mm/mmu_gather.c:403 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:496 exit_mmap+0x474/0xba0 mm/mmap.c:1297 __mmput+0x118/0x410 kernel/fork.c:1379 exit_mm+0x1da/0x2c0 kernel/exit.c:589 do_exit+0x859/0x2550 kernel/exit.c:940 do_group_exit+0x21c/0x2d0 kernel/exit.c:1102 get_signal+0x125e/0x1310 kernel/signal.c:3034 arch_do_signal_or_restart+0x95/0x780 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x8b/0x120 kernel/entry/common.c:218 do_syscall_64+0x103/0x210 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe6b538e969 Code: Unable to access opcode bytes at 0x7fe6b538e93f. RSP: 002b:00007fe6b62a30e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: 0000000000000001 RBX: 00007fe6b55b5fa8 RCX: 00007fe6b538e969 RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007fe6b55b5fac RBP: 00007fe6b55b5fa0 R08: 7fffffffffffffff R09: 0000000000000000 R10: 0000000000000128 R11: 0000000000000246 R12: 00007fe6b55b5fac R13: 0000000000000000 R14: 00007ffed0717c00 R15: 00007ffed0717ce8