INFO: rcu detected stall in __se_sys_mount

Status: fixed on 2020/12/08 16:15
Subsystems: afs
[Documentation on labels]
Reported-by: syzbot+3f2db34df769d77edf8c@syzkaller.appspotmail.com
Fix commit: 1d0e850a49a5 afs: Fix cell removal
First crash: 2224d, last: 2099d
Cause bisection: the issue happens on the oldest tested release (bisect log)
Crash: WARNING in sysfs_warn_dup (log)
Repro: syz .config
  
Fix bisection: fixed by (bisect log) :
commit 1d0e850a49a5b56f8f3cb51e74a11e2fedb96be6
Author: David Howells <dhowells@redhat.com>
Date: Fri Oct 16 12:21:14 2020 +0000

  afs: Fix cell removal

  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
INFO: rcu detected stall in __se_sys_mount 1 (4) 2020/12/08 06:33
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in mount 1 1 8d11h 8d10h 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 41 3h09m 345d 0/29 upstream: reported C repro on 2025/08/27 13:07
linux-5.15 INFO: rcu detected stall in mount origin:lts-only 1 syz, C error 5 75d 459d 0/3 upstream: reported C repro on 2025/05/05 20:18
linux-6.1 INFO: rcu detected stall in sys_mount origin:lts-only 1 syz, C inconclusive 8 44d 601d 0/3 upstream: reported C repro on 2024/12/14 21:36
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2020/12/07 16:14 3h50m bisect fix upstream OK (1) job log
2020/11/07 14:57 28m bisect fix upstream OK (0) job log log
2020/09/16 10:24 30m bisect fix upstream OK (0) job log log
2020/08/15 20:23 29m bisect fix upstream OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1):
------------[ cut here ]------------
WARNING: CPU: 1 PID: 7452 at kernel/sched/core.c:3013 rq_unlock kernel/sched/sched.h:1325 [inline]
WARNING: CPU: 1 PID: 7452 at kernel/sched/core.c:3013 try_invoke_on_locked_down_task+0x12d/0x270 kernel/sched/core.c:3019
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 7452 Comm: syz-executor259 Not tainted 5.9.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d6/0x29e lib/dump_stack.c:118
 panic+0x2c0/0x800 kernel/panic.c:231
 __warn+0x227/0x250 kernel/panic.c:600
 report_bug+0x1b1/0x2e0 lib/bug.c:198
 handle_bug+0x42/0x80 arch/x86/kernel/traps.c:234
 exc_invalid_op+0x16/0x40 arch/x86/kernel/traps.c:254
 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536
RIP: 0010:try_invoke_on_locked_down_task+0x12d/0x270 kernel/sched/sched.h:1325
Code: f8 48 c1 e8 03 42 8a 04 38 84 c0 0f 85 10 01 00 00 8b 74 24 18 48 89 ef e8 90 47 09 00 4c 89 ef e8 88 9b fd 06 e9 a4 00 00 00 <0f> 0b e9 2b ff ff ff 48 c7 c1 74 fb af 89 80 e1 07 80 c1 03 38 c1
RSP: 0018:ffffc90000da8c50 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffffffff896ff600 RCX: 0013916f856b3a00
RDX: ffffc90000da8d00 RSI: ffffffff8162d990 RDI: ffff88809027e480
RBP: ffffffff8162d990 R08: dffffc0000000000 R09: fffffbfff12df8f9
R10: fffffbfff12df8f9 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff896ff600 R14: ffff88809027e480 R15: dffffc0000000000
 rcu_print_task_stall kernel/rcu/tree_stall.h:267 [inline]
 print_other_cpu_stall kernel/rcu/tree_stall.h:475 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:634 [inline]
 rcu_pending kernel/rcu/tree.c:3639 [inline]
 rcu_sched_clock_irq+0x12bc/0x1eb0 kernel/rcu/tree.c:2521
 update_process_times+0x130/0x1b0 kernel/time/timer.c:1710
 tick_sched_handle kernel/time/tick-sched.c:176 [inline]
 tick_sched_timer+0x25e/0x410 kernel/time/tick-sched.c:1328
 __run_hrtimer kernel/time/hrtimer.c:1524 [inline]
 __hrtimer_run_queues+0x42d/0x930 kernel/time/hrtimer.c:1588
 hrtimer_interrupt+0x373/0xd60 kernel/time/hrtimer.c:1650
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0xf0/0x260 arch/x86/kernel/apic/apic.c:1097
 asm_call_irq_on_stack+0xf/0x20
 </IRQ>
 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline]
 run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline]
 sysvec_apic_timer_interrupt+0x94/0xf0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
RIP: 0010:strncasecmp+0x0/0x1c0 lib/string.c:44
Code: 2b 09 f2 48 01 c8 89 ce c1 e6 11 48 c1 e9 2f 09 f1 89 c6 31 ce 48 c1 e8 20 31 f0 31 d0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc <55> 41 57 41 56 41 55 41 54 53 48 83 ec 10 48 85 d2 0f 84 80 01 00
RSP: 0018:ffffc90006357b98 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000007 RCX: dffffc0000000000
RDX: 0000000000000007 RSI: ffff88809752ce81 RDI: ffff88809eedc100
RBP: 0000000000000007 R08: ffffffff82dd8855 R09: ffffed1014220716
R10: ffffed1014220716 R11: 0000000000000000 R12: 00000000000009a0
R13: ffff88809eedc100 R14: 0000000000000007 R15: ffff8880a1103800
 afs_lookup_cell_rcu+0x2bc/0x6f0 fs/afs/cell.c:88
 afs_lookup_cell+0x246/0x14d0 fs/afs/cell.c:249
 afs_parse_source fs/afs/super.c:290 [inline]
 afs_parse_param+0x526/0x790 fs/afs/super.c:326
 vfs_parse_fs_param+0x1e5/0x460 fs/fs_context.c:117
 vfs_parse_fs_string fs/fs_context.c:161 [inline]
 generic_parse_monolithic+0x230/0x350 fs/fs_context.c:201
 do_new_mount fs/namespace.c:2871 [inline]
 path_mount+0x176c/0x29e0 fs/namespace.c:3192
 do_mount fs/namespace.c:3205 [inline]
 __do_sys_mount fs/namespace.c:3413 [inline]
 __se_sys_mount+0x126/0x180 fs/namespace.c:3390
 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x447a3a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d a3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 7a a3 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffc915e4f78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc915e4fc0 RCX: 0000000000447a3a
RDX: 0000000020000000 RSI: 0000000020000040 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007ffc915e4fc0 R09: 0000000000000004
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402240
R13: 00000000004022d0 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/10/08 12:14 upstream c85fb28b6f99 1880b4a9 .config console log report syz C ci-upstream-kasan-gce-smack-root
2020/07/05 21:44 upstream 7cc2a8ea1048 51095195 .config console log report syz ci-upstream-kasan-gce-smack-root
* Struck through repros no longer work on HEAD.