syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=06ac/1/0x4000000000000000 softirq=23451/23451 fqs=9
rcu: 	(detected by 0, t=10502 jiffies, g=19585, q=372 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 7269 Comm: syz.0.418 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:26 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:109 [inline]
RIP: 0010:arch_irqs_disabled arch/x86/include/asm/irqflags.h:151 [inline]
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x2b/0x80 kernel/locking/spinlock.c:198
Code: 0f 1e fa 55 48 89 f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 56 6d 4b f6 48 89 df e8 de bc 4b f6 f7 c5 00 02 00 00 75 23 9c <58> f6 c4 02 75 37 bf 01 00 00 00 e8 a5 ce 3a f6 65 8b 05 ae d8 76
RSP: 0018:ffffc90000a08e78 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffff8880b8528400 RCX: ffffffff81e54493
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8880b8528400
RBP: 0000000000000046 R08: 0000000000000000 R09: ffffed10170a5080
R10: ffff8880b8528403 R11: ffffc90000a08ff8 R12: ffff88802eb1b300
R13: ffffffff89a52f10 R14: ffff8880b8528640 R15: ffff8880b8528690
FS:  00007fc2a5f976c0(0000) GS:ffff88812441a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000316030 CR3: 000000002b949000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 __run_hrtimer kernel/time/hrtimer.c:2028 [inline]
 __hrtimer_run_queues+0x37b/0x9c0 kernel/time/hrtimer.c:2096
 hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2215
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
 __sysvec_apic_timer_interrupt+0x109/0x470 arch/x86/kernel/apic/apic.c:1068
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:get_current arch/x86/include/asm/current.h:23 [inline]
RIP: 0010:write_comp_data+0x10/0x90 kernel/kcov.c:245
Code: 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 65 8b 05 19 08 07 12 49 89 f8 49 89 f1 49 89 d2 <65> 48 8b 3d f0 07 07 12 a9 00 01 ff 00 74 1b f6 c4 01 74 07 a9 00
RSP: 0018:ffffc90004c57a30 EFLAGS: 00000246
RAX: 0000000080000000 RBX: 0000000000000001 RCX: ffffffff84fea114
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000008
R13: ffffc90004c57b90 R14: ffffc90004c57d98 R15: 0000000000000000
 in_x32_syscall arch/x86/include/asm/compat.h:86 [inline]
 in_32bit_syscall arch/x86/include/asm/compat.h:94 [inline]
 in_compat_syscall arch/x86/include/asm/compat.h:100 [inline]
 import_iovec+0xd4/0x130 lib/iov_iter.c:1441
 copy_msghdr_from_user+0x2c6/0x4c0 net/socket.c:2621
 recvmsg_copy_msghdr net/socket.c:2870 [inline]
 ___sys_recvmsg+0xdd/0x1a0 net/socket.c:2942
 do_recvmmsg+0x2f3/0x740 net/socket.c:3041
 __sys_recvmmsg net/socket.c:3115 [inline]
 __do_sys_recvmmsg net/socket.c:3138 [inline]
 __se_sys_recvmmsg net/socket.c:3131 [inline]
 __x64_sys_recvmmsg+0x22a/0x280 net/socket.c:3131
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc2a519ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc2a5f97028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007fc2a5416090 RCX: 00007fc2a519ce59
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007fc2a5232e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc2a5416128 R14: 00007fc2a5416090 R15: 00007ffe4d79e728
 </TASK>
rcu: rcu_preempt kthread starved for 10484 jiffies! g19585 f0x0 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:29168 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5504 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7228
 __schedule_loop kernel/sched/core.c:7307 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7322
 schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2123
 rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2325
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 13 Comm: kworker/u8:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: writeback wb_workfn (flush-8:0)
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0x589/0x16c0 kernel/smp.c:892
Code: b8 00 00 00 00 00 fc ff df 48 8b 54 24 08 49 89 d5 49 89 d4 49 c1 ed 03 41 83 e4 07 49 01 c5 41 83 c4 03 e8 b9 95 0c 00 f3 90 <41> 0f b6 45 00 41 38 c4 7c 08 84 c0 0f 85 2c 0f 00 00 8b 45 08 31
RSP: 0018:ffffc90000126820 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff81fcc98d
RDX: ffff88801e2c8000 RSI: ffffffff81fcc967 RDI: ffff88801e2c8000
RBP: ffff8880b85410c0 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000000751b R12: 0000000000000003
R13: ffffed10170a8219 R14: 0000000000000001 R15: ffff8880b843c700
FS:  0000000000000000(0000) GS:ffff88812431a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b332fcff8 CR3: 00000000743e1000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1057
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline]
 flush_tlb_mm_range+0x45f/0x16f0 arch/x86/mm/tlb.c:1451
 flush_tlb_page arch/x86/include/asm/tlbflush.h:345 [inline]
 ptep_clear_flush+0x148/0x170 mm/pgtable-generic.c:104
 page_vma_mkclean_one.constprop.0+0x3a2/0x7b0 mm/rmap.c:1138
 page_mkclean_one+0x1cd/0x2b0 mm/rmap.c:1186
 __rmap_walk_file+0x383/0x680 mm/rmap.c:3064
 rmap_walk_file+0x1d8/0x2a0 mm/rmap.c:3097
 rmap_walk mm/rmap.c:3108 [inline]
 folio_mkclean+0x2af/0x4e0 mm/rmap.c:1218
 folio_clear_dirty_for_io+0x1ba/0x960 mm/page-writeback.c:2909
 mpage_submit_folio+0x84/0x330 fs/ext4/inode.c:2085
 mpage_process_page_bufs+0x473/0x8d0 fs/ext4/inode.c:2215
 mpage_prepare_extent_to_map+0xb50/0x1920 fs/ext4/inode.c:2754
 ext4_do_writepages+0x9f9/0x3ed0 fs/ext4/inode.c:2895
 ext4_writepages+0x347/0x750 fs/ext4/inode.c:3043
 do_writepages+0x278/0x600 mm/page-writeback.c:2571
 __writeback_single_inode+0x164/0x1300 fs/fs-writeback.c:1787
 writeback_sb_inodes+0x766/0x1c50 fs/fs-writeback.c:2079
 __writeback_inodes_wb+0xf8/0x2d0 fs/fs-writeback.c:2155
 wb_writeback+0x6f6/0xb50 fs/fs-writeback.c:2266
 wb_check_old_data_flush fs/fs-writeback.c:2370 [inline]
 wb_do_writeback fs/fs-writeback.c:2449 [inline]
 wb_workfn+0x93f/0xc80 fs/fs-writeback.c:2477
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>