syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 1, t=10502 jiffies, g=9913, q=306 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10498 (4294956628-4294946130), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10499 jiffies! g9913 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:27088 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </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: 5861 Comm: syz-executor303 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:lockdep_softirqs_off+0x1dd/0x430 kernel/locking/lockdep.c:4537
Code: 84 c0 0f 85 da 01 00 00 44 89 3b 48 c7 c0 80 a4 ea 96 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 dc 01 00 00 83 3d 13 c5 83 15 00 <75> 0e 65 8b 05 92 da 9c 7e a9 00 ff 00 00 74 75 48 c7 44 24 20 0e
RSP: 0018:ffffc90004b2f9c0 EFLAGS: 00000046
RAX: 0000000000000004 RBX: ffff88807ba7e4a8 RCX: ffffffff96eaa403
RDX: ffff88807ba7da00 RSI: 0000000000000200 RDI: ffffffff813147de
RBP: ffffc90004b2fa70 R08: ffffc90004b2fc7f R09: 1ffff92000965f8f
R10: dffffc0000000000 R11: fffff52000965f90 R12: ffff88807ba7e498
R13: dffffc0000000000 R14: 1ffff92000965f3c R15: 0000000003a3f9ee
FS:  00005555929c73c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 0000000031dcb000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 __local_bh_disable_ip+0xb3/0x190 kernel/softirq.c:346
 local_bh_disable include/linux/bottom_half.h:20 [inline]
 fpregs_lock arch/x86/include/asm/fpu/api.h:72 [inline]
 restore_fpregs_from_user arch/x86/kernel/fpu/signal.c:285 [inline]
 __fpu_restore_sig arch/x86/kernel/fpu/signal.c:359 [inline]
 fpu__restore_sig+0x417/0x10e0 arch/x86/kernel/fpu/signal.c:493
 restore_sigcontext arch/x86/kernel/signal_64.c:95 [inline]
 __ia32_sys_rt_sigreturn+0x65d/0x7b0 arch/x86/kernel/signal_64.c:266
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7eff17f4cea0
Code: 0f 1f 84 00 00 00 00 00 66 90 80 3d 11 a2 08 00 00 74 17 b8 03 00 00 00 0f 05 48 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 <48> 83 ec 18 89 7c 24 0c e8 23 87 02 00 8b 7c 24 0c 89 c2 b8 03 00
RSP: 002b:00007ffc612f73a8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007eff17f4de39
RDX: 000020000006b000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007eff17fa4469
R13: 0000000000000001 R14: 00007ffc612f73e0 R15: 0000000000000000
 </TASK>