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INFO: rcu detected stall in sys_readlink (3)

Status: upstream: reported on 2025/02/12 04:41
Reported-by: syzbot+1d15e0d85a0d266298e1@syzkaller.appspotmail.com
First crash: 138d, last: 6d03h
▶ ▼ Similar bugs (10)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_readlink (2) kernel 3 901d 960d 0/29 auto-obsoleted due to no activity on 2023/04/24 08:02
linux-5.15 INFO: rcu detected stall in sys_readlink 1 670d 670d 0/3 auto-obsoleted due to no activity on 2023/12/08 09:32
upstream INFO: rcu detected stall in sys_readlink fs 1 1164d 1164d 0/29 auto-closed as invalid on 2022/07/22 05:22
linux-5.15 INFO: rcu detected stall in sys_readlink (2) 3 334d 359d 0/3 auto-obsoleted due to no activity on 2024/11/07 23:07
upstream INFO: rcu detected stall in sys_readlink (4) fs 2 575d 578d 0/29 auto-obsoleted due to no activity on 2024/03/02 18:22
linux-6.1 INFO: rcu detected stall in sys_readlink (2) 1 10d 10d 0/3 upstream: reported on 2025/06/20 10:17
linux-6.1 INFO: rcu detected stall in sys_readlink 4 143d 334d 0/3 auto-obsoleted due to no activity on 2025/05/18 03:23
upstream INFO: rcu detected stall in sys_readlink (3) bpf fs 2 776d 783d 0/29 auto-obsoleted due to no activity on 2023/08/14 04:05
upstream INFO: rcu detected stall in sys_readlink (5) mm fs syz done 31 5d22h 255d 0/29 upstream: reported syz repro on 2024/10/18 11:28
android-5-15 BUG: soft lockup in sys_readlink 2 385d 444d 0/2 auto-obsoleted due to no activity on 2024/09/08 11:06

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5399/1:b..l
	(detected by 0, t=10502 jiffies, g=27485, q=37)
task:udevd           state:R  running task     stack:24768 pid: 5399 ppid:  3547 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_is_held_type+0x13a/0x190 kernel/locking/lockdep.c:5671
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc900032df810 EFLAGS: 00000206
RAX: 65418bf921affd00 RBX: ffff88807ac29dc0 RCX: 65418bf921affd00
RDX: 0000000000000000 RSI: ffffffff8a0b2460 RDI: ffffffff8a59a740
RBP: 0000000000000001 R08: dffffc0000000000 R09: fffff52000067277
R10: fffff52000067277 R11: 1ffff92000067276 R12: 0000000000000000
R13: 0000000000000246 R14: ffffffff8c11bfa0 R15: ffff88807ac2a8b0
 hlist_bl_first_rcu include/linux/rculist_bl.h:24 [inline]
 __d_lookup_rcu+0x115/0x760 fs/dcache.c:2305
 lookup_fast+0x13f/0x710 fs/namei.c:1586
 walk_component+0x81/0x460 fs/namei.c:1972
 link_path_walk+0x662/0xd40 fs/namei.c:-1
 path_lookupat+0x9d/0x440 fs/namei.c:2454
 filename_lookup+0x1e2/0x4f0 fs/namei.c:2484
 user_path_at_empty+0x40/0x190 fs/namei.c:2883
 do_readlinkat+0xd4/0x480 fs/stat.c:442
 __do_sys_readlink fs/stat.c:475 [inline]
 __se_sys_readlink fs/stat.c:472 [inline]
 __x64_sys_readlink+0x7b/0x90 fs/stat.c:472
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f49382b03a7
RSP: 002b:00007ffe1792c198 EFLAGS: 00000246 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 00007ffe1792cb70 RCX: 00007f49382b03a7
RDX: 0000000000000400 RSI: 00007ffe1792c650 RDI: 00007ffe1792cb70
RBP: 00007ffe1792cb7f R08: 0000000000000075 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000246 R12: 00007ffe1792c650
R13: 00007ffe1792c250 R14: 000055ddb46e56d7 R15: 000055dde5bc3650
 </TASK>
rcu: rcu_preempt kthread starved for 10527 jiffies! g27485 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:28032 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1e0 kernel/sched/core.c:6459
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x10c8/0x1220 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+0x831/0x1110 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1754
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1816
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:default_idle+0xb/0x10 arch/x86/kernel/process.c:723
Code: bf 48 89 df e8 26 8c 12 f8 eb b5 e8 3f be f6 ff 00 00 cc cc 00 00 cc cc 00 00 cc cc 00 00 cc 66 90 0f 00 2d 97 13 5b 00 fb f4 <c3> 0f 1f 40 00 41 57 41 56 53 49 be 00 00 00 00 00 fc ff df 65 48
RSP: 0018:ffffffff8be07dc8 EFLAGS: 000002c6
RAX: 6d9f092840e23900 RBX: ffffffff8bebc3c0 RCX: 6d9f092840e23900
RDX: 0000000000000001 RSI: ffffffff8a0b11c0 RDI: ffffffff8a59a740
RBP: ffffffff8be07ef8 R08: dffffc0000000000 R09: ffffed101720765a
R10: ffffed101720765a R11: 1ffff11017207659 R12: ffffffff8d68abe8
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff17d7878
 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112
 cpuidle_idle_call kernel/sched/idle.c:194 [inline]
 do_idle+0x21b/0x5b0 kernel/sched/idle.c:306
 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403
 start_kernel+0x486/0x530 init/main.c:1140
 secondary_startup_64_no_verify+0xb1/0xbb
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/24 16:41 linux-5.15.y 1c700860e8bc e2f27c35 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_readlink
2025/05/05 19:54 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 sys_readlink
2025/02/12 04:40 linux-5.15.y c16c81c81336 f2baddf5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in sys_readlink
* Struck through repros no longer work on HEAD.