syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 1, t=10502 jiffies, g=7609, q=53 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294954998-4294944495), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10504 jiffies! g7609 f0x2 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:27288 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4291 Comm: syz-executor288 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:__sanitizer_cov_trace_cmp8+0x0/0x80 kernel/kcov.c:293
Code: 28 4d 39 ca 77 22 89 ff 89 f6 49 ff c0 4c 89 01 48 c7 44 11 08 04 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 90 <48> 8b 04 24 65 48 8b 0d 34 f8 7f 7e 65 8b 15 35 f8 7f 7e 81 e2 00
RSP: 0018:ffffc90003d87a80 EFLAGS: 00000046
RAX: dffffc0000000000 RBX: ffff8880272d00d0 RCX: ffff888078675940
RDX: 0000000000000000 RSI: 189658790c22a2f9 RDI: 189658790c22a301
RBP: 7fffffffffffffff R08: ffffffff8e1fcd2f R09: 1ffffffff1c3f9a5
R10: dffffc0000000000 R11: fffffbfff1c3f9a6 R12: 0000000000000008
R13: 189658790c22a301 R14: 189658790c22a2f9 R15: 1ffff11004e5a01a
FS:  000055557d750480(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 0000000079d6f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 hrtimer_forward+0x173/0x290 kernel/time/hrtimer.c:-1
 common_hrtimer_rearm+0x8c/0x110 kernel/time/posix-timers.c:303
 posixtimer_rearm+0x131/0x340 kernel/time/posix-timers.c:329
 dequeue_signal+0x1b6/0x4b0 kernel/signal.c:704
 get_signal+0x547/0x1350 kernel/signal.c:2751
 arch_do_signal_or_restart+0xc4/0x1350 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9e15c80711
Code: 1d 00 eb 99 0f 1f 44 00 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 d0 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f
RSP: 002b:00007ffc36ce9a58 EFLAGS: 00000217
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f9e15c80709
RDX: 000020000006b000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007f9e15cfe0b2 R09: 00007f9e15cfe0b2
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9e15cfe0b2
R13: 00007f9e15cfc12a R14: 00007ffc36ce9aa0 R15: 0000000000000000
 </TASK>