INFO: rcu detected stall in fcntl

Status: auto-obsoleted due to no activity on 2026/03/30 11:32
Reported-by: syzbot+c1193d254a7ddb7e42ca@syzkaller.appspotmail.com
First crash: 215d, last: 215d
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in fcntl (2) 1 1 33d 33d 0/3 upstream: reported on 2026/06/20 16:30
linux-5.15 INFO: rcu detected stall in fcntl 1 10 4d14h 177d 0/3 upstream: reported on 2026/01/28 08:04

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6138/1:b..l P6119/1:b..l
	(detected by 1, t=10502 jiffies, g=25585, q=34 ncpus=2)
task:syz.1.368       state:R  running task     stack:24608 pid:6119  ppid:4263   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6730
 preempt_schedule+0xa7/0xb0 kernel/sched/core.c:6754
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 unwind_next_frame+0x1892/0x20b0 arch/x86/kernel/unwind_orc.c:629
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 save_stack+0xf3/0x1e0 mm/page_owner.c:127
 __reset_page_owner+0x51/0x1a0 mm/page_owner.c:148
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page_list+0xbb/0x8e0 mm/page_alloc.c:3525
 release_pages+0x1f92/0x2200 mm/swap.c:1035
 tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
 tlb_flush_mmu+0xff/0x210 mm/mmu_gather.c:261
 zap_pte_range mm/memory.c:1525 [inline]
 zap_pmd_range mm/memory.c:1574 [inline]
 zap_pud_range mm/memory.c:1603 [inline]
 zap_p4d_range mm/memory.c:1624 [inline]
 unmap_page_range+0x1f4a/0x2500 mm/memory.c:1645
 unmap_vmas+0x22c/0x330 mm/memory.c:1730
 exit_mmap+0x1cc/0x8e0 mm/mmap.c:3250
 __mmput+0x118/0x3c0 kernel/fork.c:1200
 exit_mm+0x1e6/0x2c0 kernel/exit.c:565
 do_exit+0x8c1/0x2400 kernel/exit.c:867
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 get_signal+0x1272/0x1350 kernel/signal.c:2871
 arch_do_signal_or_restart+0xb7/0x1240 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:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f7864d8f749
RSP: 002b:00007f7865d120e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00007f7864fe5fa8 RCX: 00007f7864d8f749
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f7864fe5fac
RBP: 00007f7864fe5fa0 R08: 001abe8665f3e5be R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7864fe6038 R14: 00007ffc60411250 R15: 00007ffc60411338
 </TASK>
task:syz.8.371       state:R  running task     stack:27392 pid:6138  ppid:5876   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lock_acquire+0x20f/0x490 kernel/locking/lockdep.c:5666
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f5 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc90003c27460 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 181b9a0b0b639700
RDX: 0000000000000000 RSI: ffffffff8a6c1780 RDI: ffffffff8abef920
RBP: ffffc90003c27578 R08: dffffc0000000000 R09: fffffbfff2119049
R10: fffffbfff2119049 R11: 1ffffffff2119048 R12: 0000000000000000
R13: 1ffff92000784e98 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 is_bpf_text_address+0x43/0x2a0 kernel/bpf/core.c:735
 kernel_text_address+0x9c/0xd0 kernel/extable.c:125
 __kernel_text_address+0x9/0x30 kernel/extable.c:79
 unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
 arch_stack_walk+0xf2/0x140 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free+0xf7/0x290 mm/slub.c:3709
 locks_free_lock fs/locks.c:335 [inline]
 posix_lock_inode+0x24de/0x3220 fs/locks.c:1308
 posix_lock_file fs/locks.c:1333 [inline]
 vfs_lock_file fs/locks.c:2302 [inline]
 do_lock_file_wait fs/locks.c:2316 [inline]
 fcntl_setlk+0x95b/0x1020 fs/locks.c:2394
 do_fcntl+0x4e4/0x11c0 fs/fcntl.c:355
 __do_sys_fcntl fs/fcntl.c:446 [inline]
 __se_sys_fcntl+0xc9/0x190 fs/fcntl.c:431
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f393758f749
RSP: 002b:00007f3938345038 EFLAGS: 00000246 ORIG_RAX: 0000000000000048
RAX: ffffffffffffffda RBX: 00007f39377e5fa0 RCX: 00007f393758f749
RDX: 0000200000000380 RSI: 0000000000000026 RDI: 0000000000000007
RBP: 00007f3937613f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f39377e6038 R14: 00007f39377e5fa0 R15: 00007ffc5e4a16f8
 </TASK>
rcu: rcu_preempt kthread starved for 10592 jiffies! g25585 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:26880 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 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 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:741

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/20 11:32 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in fcntl
* Struck through repros no longer work on HEAD.