rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 1-...!: (1 GPs behind) idle=35a/1/0x4000000000000002 softirq=27099/27142 fqs=19 (t=10500 jiffies g=21001 q=365) rcu: rcu_preempt kthread starved for 10460 jiffies! g21001 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29264 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3386 [inline] __schedule+0x934/0x1f90 kernel/sched/core.c:4082 schedule+0xdc/0x2b0 kernel/sched/core.c:4156 schedule_timeout+0x486/0xc50 kernel/time/timer.c:1895 rcu_gp_fqs_loop kernel/rcu/tree.c:1658 [inline] rcu_gp_kthread+0xa10/0x1940 kernel/rcu/tree.c:1818 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 NMI backtrace for cpu 1 CPU: 1 PID: 13048 Comm: syz-executor.0 Not tainted 5.6.0-rc1-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+0x197/0x210 lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x183/0x1cf 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+0x51a/0xc37 kernel/rcu/tree.c:2276 update_process_times+0x2d/0x70 kernel/time/timer.c:1726 tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:171 tick_sched_timer+0x53/0x140 kernel/time/tick-sched.c:1314 __run_hrtimer kernel/time/hrtimer.c:1517 [inline] __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1579 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1641 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline] smp_apic_timer_interrupt+0x160/0x610 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+0x26/0x50 kernel/kcov.c:187 Code: 00 00 00 00 55 48 89 e5 65 48 8b 04 25 c0 1e 02 00 65 8b 15 64 90 8c 7e 81 e2 00 01 1f 00 48 8b 75 08 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 RSP: 0018:ffffc90004d571b8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: ffff88804a6263c0 RBX: ffffc90004d572a8 RCX: ffffc900028c9000 RDX: 0000000000000002 RSI: ffffffff87eb1dac RDI: ffffc90004d572a8 RBP: ffffc90004d571b8 R08: ffff88804a6263c0 R09: ffffed1015d2707c R10: ffffed1015d2707b R11: ffff8880ae9383db R12: ffff888093879642 R13: ffff888093879640 R14: 0000000000000000 R15: 0000000000000000 xas_descend+0x1c/0x370 lib/xarray.c:203 xas_load+0xef/0x150 lib/xarray.c:240 find_get_entry+0x144/0x7a0 mm/filemap.c:1511 pagecache_get_page+0x4c/0x9f0 mm/filemap.c:1613 grab_cache_page_write_begin+0x75/0xb0 mm/filemap.c:3237 ext4_da_write_begin+0x33b/0xc70 fs/ext4/inode.c:2966 generic_perform_write+0x23b/0x540 mm/filemap.c:3287 ext4_buffered_write_iter+0x1fe/0x460 fs/ext4/file.c:270 ext4_file_write_iter+0x1fe/0x14e0 fs/ext4/file.c:642 call_write_iter include/linux/fs.h:1901 [inline] do_iter_readv_writev+0x5f8/0x8f0 fs/read_write.c:693 do_iter_write fs/read_write.c:998 [inline] do_iter_write+0x184/0x610 fs/read_write.c:979 vfs_iter_write+0x77/0xb0 fs/read_write.c:1039 iter_file_splice_write+0x717/0xc10 fs/splice.c:760 do_splice_from fs/splice.c:863 [inline] direct_splice_actor+0x123/0x190 fs/splice.c:1037 splice_direct_to_actor+0x3b4/0xa30 fs/splice.c:992 do_splice_direct+0x1da/0x2a0 fs/splice.c:1080 do_sendfile+0x597/0xd00 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+0x15a/0x220 fs/read_write.c:1567 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c6c9 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:00007f2fc2051c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f2fc20526d4 RCX: 000000000045c6c9 RDX: 00000000200001c0 RSI: 0000000000000005 RDI: 0000000000000005 RBP: 000000000076c070 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000008cb R14: 00000000004cb58f R15: 000000000076c07c