rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10499 ticks this GP) idle=00e/1/0x4000000000000002 softirq=41916/41916 fqs=21 
	(t=10500 jiffies g=43445 q=328)
rcu: rcu_preempt kthread starved for 10455 jiffies! g43445 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: 15998 Comm: syz-executor.4 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __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
 </IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:180
Code: ff cc cc cc cc cc cc cc cc cc 65 48 8b 04 25 c0 1e 02 00 48 8b 80 98 13 00 00 c3 0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 <55> 48 89 e5 65 48 8b 04 25 c0 1e 02 00 65 8b 15 74 90 8c 7e 81 e2
RSP: 0018:ffffc900020675f0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000002 RBX: ffffea0002218f00 RCX: ffffffff81af721c
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: ffffc90002067610 R08: ffff8880a31b6640 R09: fffff940004431e1
R10: fffff940004431e0 R11: ffffea0002218f07 R12: 0000000000000000
R13: ffffea0002218f08 R14: ffffc900020676e0 R15: 0000000000000000
 find_subpage include/linux/pagemap.h:338 [inline]
 find_get_entry+0x328/0x7a0 mm/filemap.c:1533
 pagecache_get_page+0x4c/0x9f0 mm/filemap.c:1613
 find_get_page include/linux/pagemap.h:260 [inline]
 generic_file_buffered_read mm/filemap.c:2025 [inline]
 generic_file_read_iter+0x722/0x2cf0 mm/filemap.c:2302
 ext4_file_read_iter fs/ext4/file.c:131 [inline]
 ext4_file_read_iter+0x1de/0x620 fs/ext4/file.c:114
 call_read_iter include/linux/fs.h:1895 [inline]
 generic_file_splice_read+0x4af/0x800 fs/splice.c:313
 do_splice_to+0x127/0x180 fs/splice.c:892
 splice_direct_to_actor+0x320/0xa30 fs/splice.c:971
 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: 0033:0x45b3b9
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:00007f5cf7d21c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f5cf7d226d4 RCX: 000000000045b3b9
RDX: 00000000200001c0 RSI: 0000000000000005 RDI: 0000000000000005
RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000
R10: 00008080fffffffe R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000008cb R14: 00000000004ca26f R15: 000000000075c07c