INFO: rcu detected stall in mount

Status: upstream: reported C repro on 2025/05/05 20:18
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+d53e2824fe281eb14853@syzkaller.appspotmail.com
First crash: 462d, last: 78d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/07/07 linux-5.15.y (ToT) 3dea0e7f549e C [report] BUG: workqueue lockup
2025/07/07 upstream (ToT) d7b8f8e20813 C Didn't crash
▶ ▼ Similar bugs (13)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in mount 1 1 11d 11d 0/2 upstream: reported on 2026/07/31 02:07
upstream INFO: rcu detected stall in sys_mount (8) prio:low overlayfs 1 syz, C error 43 2h29m 348d 0/29 upstream: reported C repro on 2025/08/27 13:07
linux-6.1 INFO: rcu detected stall in sys_mount origin:lts-only 1 syz, C inconclusive 8 47d 604d 0/3 upstream: reported C repro on 2024/12/14 21:36
upstream INFO: rcu detected stall in __se_sys_mount afs 1 syz, C done done 2 2102d 2226d 15/29 fixed on 2020/12/08 16:15
upstream INFO: rcu detected stall in sys_mount (6) ntfs 1 syz, C inconclusive 82 1005d 1778d 0/29 auto-obsoleted due to no activity on 2024/02/18 04:52
upstream INFO: rcu detected stall in sys_mount (4) fs 1 2 2350d 2365d 0/29 auto-closed as invalid on 2020/06/02 15:48
upstream INFO: rcu detected stall in sys_mount (5) afs 1 syz, C done done 10 2140d 2161d 15/29 fixed on 2020/11/16 12:12
linux-5.15 INFO: rcu detected stall in sys_mount 1 2 606d 668d 0/3 auto-obsoleted due to no activity on 2025/03/22 20:11
upstream INFO: rcu detected stall in sys_mount (3) mm 1 6 2442d 2443d 0/29 closed as invalid on 2019/12/04 14:04
upstream INFO: rcu detected stall in sys_mount nfs 1 1 2847d 2847d 0/29 closed as invalid on 2018/10/29 13:47
upstream INFO: rcu detected stall in sys_mount (7) fs 1 syz, C inconclusive done 41 594d 837d 0/29 auto-obsoleted due to no activity on 2025/03/30 13:11
upstream INFO: rcu detected stall in sys_mount (2) exfat 1 1 2798d 2798d 0/29 closed as dup on 2018/12/12 21:01
android-5-15 BUG: soft lockup in sys_mount origin:lts 1 syz, C error 17 767d 845d 0/2 auto-obsoleted due to no activity on 2024/10/17 05:03
▶ ▼ Last patch testing requests (4)
Created Duration User Patch Repo Result
2026/06/08 01:12 19m retest repro linux-5.15.y report log
2026/03/09 09:22 13m retest repro linux-5.15.y report log
2025/12/28 22:14 14m retest repro linux-5.15.y report log
2025/10/18 18:13 14m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (6)
Created Duration User Patch Repo Result
2026/06/13 01:01 12m fix candidate upstream error job log
2026/04/24 20:06 15m fix candidate upstream error job log
2026/03/25 16:44 1m fix candidate upstream error job log
2026/02/23 08:10 1m fix candidate upstream error job log
2026/01/23 20:25 1m fix candidate upstream error job log
2025/08/09 11:06 0m bisect fix linux-5.15.y error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4048/1:b..l
	(detected by 1, t=10502 jiffies, g=4249, q=193)
task:syz-executor124 state:R  running task     stack:    0 pid: 4048 ppid:  4040 flags:0x0000000c
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 preempt_schedule_irq+0x90/0x214 kernel/sched/core.c:6780
 arm64_preempt_schedule_irq+0x14c/0x21c arch/arm64/kernel/entry-common.c:260
 el1_interrupt+0x40/0x58 arch/arm64/kernel/entry-common.c:463
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline]
 lock_acquire+0x234/0x620 kernel/locking/lockdep.c:5626
 rcu_lock_acquire+0x40/0x4c include/linux/rcupdate.h:312
 rcu_read_lock include/linux/rcupdate.h:739 [inline]
 lookup_mnt+0x30/0x2ec fs/namespace.c:654
 __traverse_mounts+0x16c/0x4c8 fs/namei.c:1340
 traverse_mounts fs/namei.c:1387 [inline]
 handle_mounts fs/namei.c:1498 [inline]
 step_into+0x1cc/0xa24 fs/namei.c:1806
 walk_component+0x1f0/0x3a8 fs/namei.c:1982
 lookup_last fs/namei.c:2431 [inline]
 path_lookupat+0x13c/0x3d0 fs/namei.c:2455
 filename_lookup+0x180/0x414 fs/namei.c:2484
 kern_path+0x4c/0x190 fs/namei.c:2582
 do_loopback+0xc8/0x3c0 fs/namespace.c:2386
 path_mount+0x4cc/0x1000 fs/namespace.c:3338
 do_mount fs/namespace.c:3357 [inline]
 __do_sys_mount fs/namespace.c:3565 [inline]
 __se_sys_mount fs/namespace.c:3542 [inline]
 __arm64_sys_mount+0x514/0x5e4 fs/namespace.c:3542
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
rcu: rcu_preempt kthread starved for 10496 jiffies! g4249 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:    0 pid:   15 ppid:     2 flags:0x00000008
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 preempt_schedule_common+0x138/0x218 kernel/sched/core.c:6552
 preempt_schedule+0x64/0x84 kernel/sched/core.c:6577
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
 _raw_spin_unlock_irqrestore+0x108/0x14c kernel/locking/spinlock.c:194
 __mod_timer+0x6e8/0xb44 kernel/time/timer.c:1065
 schedule_timeout+0x17c/0x2c8 kernel/time/timer.c:1913
 rcu_gp_fqs_loop+0x25c/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xc4/0x2a8 kernel/rcu/tree.c:2145
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 1:
task:syz-executor124 state:R  running task     stack:    0 pid: 4056 ppid:  4046 flags:0x00000001
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 sched_show_task+0x3c8/0x4b4 kernel/sched/core.c:8640
 dump_cpu_task+0x84/0xa8 kernel/sched/core.c:10927
 rcu_check_gp_kthread_starvation+0x1e8/0x274 kernel/rcu/tree_stall.h:488
 print_other_cpu_stall+0x1a24/0x1c10 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3932 [inline]
 rcu_sched_clock_irq+0x1558/0x1810 kernel/rcu/tree.c:2619
 update_process_times+0x1c4/0x260 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x30c/0x4bc kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x3fc/0xb6c kernel/time/hrtimer.c:1754
 hrtimer_interrupt+0x2bc/0xb5c kernel/time/hrtimer.c:1816
 timer_handler drivers/clocksource/arm_arch_timer.c:659 [inline]
 arch_timer_handler_virt+0x74/0x88 drivers/clocksource/arm_arch_timer.c:670
 handle_percpu_devid_irq+0x29c/0x76c kernel/irq/chip.c:930
 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
 handle_irq_desc kernel/irq/irqdesc.c:652 [inline]
 handle_domain_irq+0x144/0x1fc kernel/irq/irqdesc.c:707
 gic_handle_irq+0x78/0x1c8 drivers/irqchip/irq-gic-v3.c:765
 call_on_irq_stack+0x24/0x30 arch/arm64/kernel/entry.S:855
 do_interrupt_handler+0x6c/0x88 arch/arm64/kernel/entry-common.c:267
 el1_interrupt+0x30/0x58 arch/arm64/kernel/entry-common.c:454
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
 arch_local_irq_restore+0x8/0x10 arch/arm64/include/asm/irqflags.h:122
 lock_is_held include/linux/lockdep.h:287 [inline]
 ___might_sleep+0x48/0x4d4 kernel/sched/core.c:9605
 __might_sleep+0x98/0x124 kernel/sched/core.c:9593
 __might_fault+0x80/0x128 mm/memory.c:5354
 setup_sigframe arch/arm64/kernel/signal.c:630 [inline]
 setup_rt_frame arch/arm64/kernel/signal.c:792 [inline]
 handle_signal arch/arm64/kernel/signal.c:833 [inline]
 do_signal arch/arm64/kernel/signal.c:908 [inline]
 do_notify_resume+0xcbc/0x3128 arch/arm64/kernel/signal.c:946
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
 el0_svc+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/05 21:00 linux-5.15.y 3dea0e7f549e 4f67c4ae .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in sys_mount
2026/05/24 18:09 linux-5.15.y 241d66fa280c c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in mount
2026/05/12 22:44 linux-5.15.y de8dfb3f0278 a0949470 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in mount
2025/07/09 10:25 linux-5.15.y 3dea0e7f549e f4e5e155 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in mount
2025/05/05 20:17 linux-5.15.y 16fdf2c7111b 6ca47dd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in mount
* Struck through repros no longer work on HEAD.