rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-...!: (1 GPs behind) idle=5fa/1/0x4000000000000002 softirq=27499/27513 fqs=11 (t=10500 jiffies g=22025 q=212) rcu: rcu_preempt kthread starved for 10478 jiffies! g22025 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29384 10 2 0x80004000 Call Trace: schedule+0xd0/0x2a0 kernel/sched/core.c:4154 schedule_timeout+0x474/0xba0 kernel/time/timer.c:1895 rcu_gp_fqs_loop kernel/rcu/tree.c:1658 [inline] rcu_gp_kthread+0x9d9/0x17d0 kernel/rcu/tree.c:1818 kthread+0x357/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 NMI backtrace for cpu 0 CPU: 0 PID: 12673 Comm: syz-executor.4 Not tainted 5.6.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x231/0x27e lib/nmi_backtrace.c:62 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x169/0x1b3 kernel/rcu/tree_stall.h:254 print_cpu_stall kernel/rcu/tree_stall.h:475 [inline] check_cpu_stall kernel/rcu/tree_stall.h:549 [inline] rcu_pending kernel/rcu/tree.c:3030 [inline] rcu_sched_clock_irq.cold+0x518/0xc55 kernel/rcu/tree.c:2276 update_process_times+0x25/0x60 kernel/time/timer.c:1726 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:171 tick_sched_timer+0x4e/0x140 kernel/time/tick-sched.c:1314 __run_hrtimer kernel/time/hrtimer.c:1517 [inline] __hrtimer_run_queues+0x32c/0xdd0 kernel/time/hrtimer.c:1579 hrtimer_interrupt+0x312/0x770 kernel/time/hrtimer.c:1641 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline] smp_apic_timer_interrupt+0x15b/0x600 arch/x86/kernel/apic/apic.c:1144 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 RIP: 0010:__sanitizer_cov_trace_pc+0x37/0x50 kernel/kcov.c:192 Code: f9 8f 7e 81 e2 00 01 1f 00 48 8b 34 24 75 2b 8b 90 80 13 00 00 83 fa 02 75 20 48 8b 88 88 13 00 00 8b 80 84 13 00 00 48 8b 11 <48> 83 c2 01 48 39 d0 76 07 48 89 34 d1 48 89 11 c3 0f 1f 84 00 00 RSP: 0018:ffffc90001d972d8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: 0000000000040000 RBX: 0000000000000004 RCX: ffffc90013394000 RDX: 000000000003ffff RSI: ffffffff818f92fb RDI: 0000000000000001 RBP: ffffea000226f700 R08: ffff8880923704c0 R09: fffff520003b2e64 R10: fffff520003b2e63 R11: 0000000000000003 R12: ffffea000226f734 R13: 0000000000000001 R14: dffffc0000000000 R15: ffffc90001d97318 atomic_fetch_add_unless include/linux/atomic-fallback.h:1093 [inline] atomic_add_unless include/linux/atomic-fallback.h:1111 [inline] page_ref_add_unless include/linux/page_ref.h:157 [inline] __page_cache_add_speculative include/linux/pagemap.h:186 [inline] page_cache_get_speculative include/linux/pagemap.h:202 [inline] find_get_entry+0x21b/0x770 mm/filemap.c:1521 pagecache_get_page+0x47/0xa10 mm/filemap.c:1613 grab_cache_page_write_begin+0x6d/0xa0 mm/filemap.c:3237 ext4_da_write_begin+0x314/0xbc0 fs/ext4/inode.c:2966 generic_perform_write+0x20a/0x4e0 mm/filemap.c:3287 ext4_buffered_write_iter+0x1f7/0x450 fs/ext4/file.c:270 ext4_file_write_iter+0x1ec/0x13f0 fs/ext4/file.c:642 call_write_iter include/linux/fs.h:1902 [inline] do_iter_readv_writev+0x59c/0x840 fs/read_write.c:693 do_iter_write fs/read_write.c:998 [inline] do_iter_write+0x185/0x600 fs/read_write.c:979 vfs_iter_write+0x70/0xa0 fs/read_write.c:1039 iter_file_splice_write+0x684/0xb00 fs/splice.c:760 do_splice_from fs/splice.c:863 [inline] direct_splice_actor+0x115/0x160 fs/splice.c:1037 splice_direct_to_actor+0x38c/0x980 fs/splice.c:992 do_splice_direct+0x1a8/0x270 fs/splice.c:1080 do_sendfile+0x549/0xc40 fs/read_write.c:1520 __do_sys_sendfile64 fs/read_write.c:1575 [inline] __se_sys_sendfile64 fs/read_write.c:1567 [inline] __x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1567 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c849 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f5eb1a46c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f5eb1a476d4 RCX: 000000000045c849 RDX: 00000000200001c0 RSI: 0000000000000007 RDI: 0000000000000007 RBP: 000000000076c0e0 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000008d0 R14: 00000000004cb74a R15: 000000000076c0ec