syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1):
 P25938/1:b..l

rcu: 	(detected by 0, t=10502 jiffies, g=195617, q=450 ncpus=2)
task:syz.1.5450      state:R
  running task     stack:25928 pid:25938 tgid:25937 ppid:17270  task_flags:0x40054c flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5260 [inline]
 __schedule+0x1522/0x51d0 kernel/sched/core.c:6867
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:7051
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3f/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 zap_pte_range mm/memory.c:1888 [inline]
 zap_pmd_range mm/memory.c:1950 [inline]
 zap_pud_range mm/memory.c:1978 [inline]
 zap_p4d_range mm/memory.c:1999 [inline]
 unmap_page_range+0x38fd/0x4030 mm/memory.c:2020
 unmap_single_vma mm/memory.c:2062 [inline]
 unmap_vmas+0x3c0/0x5c0 mm/memory.c:2104
 exit_mmap+0x251/0xb30 mm/mmap.c:1277
 __mmput+0x118/0x430 kernel/fork.c:1174
 exit_mm+0x168/0x220 kernel/exit.c:581
 do_exit+0x62e/0x2310 kernel/exit.c:959
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1112
 get_signal+0x1284/0x1330 kernel/signal.c:3034
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2b7/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5a5f19bf79
RSP: 002b:00007f5a60006028 EFLAGS: 00000246
 ORIG_RAX: 0000000000000001
RAX: 00000000006ab000 RBX: 00007f5a5f415fa0 RCX: 00007f5a5f19bf79
RDX: 00000000fffffd2c RSI: 0000200000000000 RDI: 0000000000000004
RBP: 00007f5a5f2327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5a5f416038 R14: 00007f5a5f415fa0 R15: 00007f5a5f53fa48
 </TASK>
rcu: rcu_preempt kthread starved for 8271 jiffies! g195617 f0x0 RCU_GP_DOING_FQS(6) ->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:27640 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5260 [inline]
 __schedule+0x1522/0x51d0 kernel/sched/core.c:6867
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7194
 irqentry_exit+0x597/0x620 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:rcu_gp_fqs kernel/rcu/tree.c:2054 [inline]
RIP: 0010:rcu_gp_fqs_loop+0xf23/0x11d0 kernel/rcu/tree.c:2117
Code: b0 d9 ef 8f 80 e1 07 80 c1 03 38 c1 0f 8c 3b f9 ff ff 48 c7 c7 b0 d9 ef 8f e8 f9 ec 81 00 e9 2a f9 ff ff 0f b7 05 05 20 ab 0c <a8> 02 74 68 48 c7 c7 40 dd 55 8e e8 7d f6 f2 09 66 83 25 ed 1f ab
RSP: 0018:ffffc90000157be0 EFLAGS: 00000246

RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 00000000ffffffff
RBP: ffffc90000157d30 R08: ffffffff8fefa777 R09: 1ffffffff1fdf4ee
R10: dffffc0000000000 R11: fffffbfff1fdf4ef R12: ffffffff8e55e240
R13: ffffffff8e55ddf0 R14: ffffffff8e55dd98 R15: 0000000000000246
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2297
 kthread+0x388/0x470 kernel/kthread.c:467
 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: 68 5d 02 e9 d3 e8 02 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 13 47 0e 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e207dc0 EFLAGS: 00000246

RAX: 000000000152081d RBX: ffffffff8199695d RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8dcd337e RDI: ffffffff8c078580
RBP: ffffffff8e207eb0 R08: ffff8880b863371b R09: 1ffff110170c66e3
R10: dffffc0000000000 R11: ffffed10170c66e4 R12: ffffffff8fefa770
R13: 1ffffffff1c529d8 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881256d7000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055c1688b74b0 CR3: 00000000771c0000 CR4: 00000000003526f0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000000
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/kernel/process.c:766 [inline]
 default_idle+0x9/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x1bd/0x500 kernel/sched/idle.c:332
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:430
 rest_init+0x2de/0x300 init/main.c:757
 start_kernel+0x380/0x3d0 init/main.c:1206
 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x147
 </TASK>