syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P18102/1:b..l
	(detected by 0, t=10502 jiffies, g=97461, q=15)
task:syz.3.4298      state:R  running task     stack:27840 pid:18102 ppid:  4184 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:copy_creds+0x414/0xd00 kernel/cred.c:361
Code: 21 58 08 89 c5 31 ff 89 c6 e8 98 b5 27 00 85 ed 74 1f e8 9f ea 12 00 89 c5 31 ff 89 c6 e8 84 b5 27 00 85 ed 0f 84 8e 00 00 00 <e8> 17 b2 27 00 eb 05 e8 10 b2 27 00 49 be 00 00 00 00 00 fc ff df
RSP: 0018:ffffc9000310f9b0 EFLAGS: 00000202
RAX: ffffffff815011fc RBX: ffff88801fbc4b40 RCX: ffff88807772bb80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: dffffc0000000000 R09: fffffbfff1ff6e19
R10: fffffbfff1ff6e19 R11: 1ffffffff1ff6e18 R12: ffff88807d5a08b0
R13: 1ffff1100fab4115 R14: dffffc0000000000 R15: ffff88801fbc4b58
 copy_process+0x87a/0x3e00 kernel/fork.c:2153
 kernel_clone+0x219/0x930 kernel/fork.c:2679
 __do_sys_clone3 kernel/fork.c:2954 [inline]
 __se_sys_clone3+0x2d5/0x360 kernel/fork.c:2938
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f95a5ff8449
RSP: 002b:00007ffcfe3f2f68 EFLAGS: 00000206 ORIG_RAX: 00000000000001b3
RAX: ffffffffffffffda RBX: 00007f95a5f7a830 RCX: 00007f95a5ff8449
RDX: 00007f95a5f7a830 RSI: 0000000000000058 RDI: 00007ffcfe3f2fb0
RBP: 00007f95a3e0a6c0 R08: 00007f95a3e0a6c0 R09: 00007ffcfe3f3097
R10: 0000000000000008 R11: 0000000000000206 R12: ffffffffffffffa8
R13: 000000000000006e R14: 00007ffcfe3f2fb0 R15: 00007ffcfe3f3098
 </TASK>
rcu: rcu_preempt kthread starved for 10330 jiffies! g97461 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:28032 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1e0 kernel/sched/core.c:6459
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:728