INFO: rcu detected stall in sys_getpid

Status: upstream: reported C repro on 2025/09/06 16:11
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+35993bdd136c7a8427a4@syzkaller.appspotmail.com
First crash: 347d, last: 17d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/09/08 linux-6.6.y (ToT) 355bd0b51d2f C [report] INFO: rcu detected stall in corrupted
2025/09/08 upstream (ToT) 76eeb9b8de98 C Didn't crash
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in sys_getpid (3) 1 syz, C 6 1d16h 91d 0/3 upstream: reported C repro on 2026/05/20 20:58
upstream INFO: rcu detected stall in sys_getpid kernel 1 5 242d 392d 0/29 auto-obsoleted due to no activity on 2026/03/20 23:07
linux-5.15 INFO: rcu detected stall in sys_getpid 1 1 784d 784d 0/3 auto-obsoleted due to no activity on 2024/10/04 19:18
linux-6.1 INFO: rcu detected stall in sys_getpid 1 1 481d 481d 0/3 auto-obsoleted due to no activity on 2025/08/03 12:49
linux-6.1 INFO: rcu detected stall in sys_getpid (2) 1 2 199d 260d 0/3 auto-obsoleted due to no activity on 2026/05/12 11:26
linux-5.15 INFO: rcu detected stall in sys_getpid (2) origin:lts-only 1 syz, C error 24 17d 627d 0/3 upstream: reported C repro on 2024/11/30 21:19
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/09/28 16:26 2h06m fix candidate upstream OK (0) 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): P5139/1:b..l P60/2:b..l P6647/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=16125, q=468 ncpus=2)
task:syz.3.337       state:R  running task     stack:25384 pid:6647  ppid:5916   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:pid_nr_ns kernel/pid.c:482 [inline]
RIP: 0010:__task_pid_nr_ns+0x28c/0x470 kernel/pid.c:503
Code: 2a 97 2d 00 31 ed e9 90 00 00 00 e8 1e 97 2d 00 31 ed e9 84 00 00 00 49 c1 e7 04 4e 8d a4 3b d8 00 00 00 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 65 0b 86 00 4d 39 34 24 74 38 e8
RSP: 0018:ffffc9000c4a7ed8 EFLAGS: 00000a02
RAX: 1ffff110050a6185 RBX: ffff888028530b40 RCX: 0000000000000000
RDX: ffff888076b1da00 RSI: 0000000000000001 RDI: 0000000000000001
RBP: 0000000000000001 R08: dffffc0000000000 R09: 1ffffffff22378a0
R10: dffffc0000000000 R11: fffffbfff22378a1 R12: ffff888028530c28
R13: dffffc0000000000 R14: ffff88805cc74aa0 R15: 0000000000000010
 task_tgid_vnr include/linux/sched.h:1649 [inline]
 __ia32_sys_getpid+0x1d/0x20 kernel/sys.c:960
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f151f196bd7
RSP: 002b:00007ffd66894f48 EFLAGS: 00000206 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007ffd668950b0 RCX: 00007f151f196bd7
RDX: 00007ffd66894f80 RSI: 00007ffd668950b0 RDI: 0000000000000021
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 00007f151f415fa0 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f151f415fac R14: 00007f151f415fa8 R15: 00007f151f415fa0
 </TASK>
task:kworker/u4:4    state:R  running task     stack:22736 pid:60    ppid:2      flags:0x00004000
Workqueue: events_unbound cfg80211_wiphy_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900015b76c0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 061ae7fddcd68500
RDX: 0000000000000000 RSI: ffffffff8acadce0 RDI: ffffffff8b1c7be0
RBP: ffffc900015b77d0 R08: dffffc0000000000 R09: 1ffffffff22378a0
R10: dffffc0000000000 R11: fffffbfff22378a1 R12: 1ffff920002b6ee4
R13: ffffffff8d131da0 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 sta_info_get+0x6b/0x2a0 net/mac80211/sta_info.c:204
 ieee80211_update_sta_info net/mac80211/ibss.c:1004 [inline]
 ieee80211_rx_bss_info net/mac80211/ibss.c:1122 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1613 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x10cb/0x2dc0 net/mac80211/ibss.c:1642
 ieee80211_iface_process_skb net/mac80211/iface.c:1655 [inline]
 ieee80211_iface_work+0x730/0xc90 net/mac80211/iface.c:1709
 cfg80211_wiphy_work+0x228/0x260 net/wireless/core.c:437
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
task:udevd           state:R  running task     stack:24680 pid:5139  ppid:1      flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x111/0x120 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 __wake_up_common_lock kernel/sched/wait.c:140 [inline]
 __wake_up_sync_key+0x12c/0x1a0 kernel/sched/wait.c:213
 sock_def_readable+0x1e1/0x420 net/core/sock.c:3363
 __netlink_sendskb net/netlink/af_netlink.c:1266 [inline]
 netlink_sendskb+0x9b/0x130 net/netlink/af_netlink.c:1272
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb3c66a7407
RSP: 002b:00007fff47c3a810 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb3c6dfd880 RCX: 00007fb3c66a7407
RDX: 0000000000000000 RSI: 00007fff47c3a870 RDI: 0000000000000004
RBP: 00005615827e45a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00000000000000b3
R13: 00005615827b79e0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10584 jiffies! g16125 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:26856 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x111/0x120 kernel/locking/spinlock.c:194
 __mod_timer+0x9b0/0xd60 kernel/time/timer.c:1134
 schedule_timeout+0x183/0x2d0 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x30d/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6651 Comm: syz.2.334 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:trace_lock_acquire include/trace/events/lock.h:24 [inline]
RIP: 0010:lock_acquire+0xbf/0x420 kernel/locking/lockdep.c:5725
Code: 7e 83 f8 08 0f 83 a0 01 00 00 41 89 c6 c1 e8 06 48 8d 3c c5 e8 e5 8a 8e be 08 00 00 00 e8 19 58 77 00 4c 0f a3 35 79 e2 22 0d <73> 0d e8 5a b3 08 00 84 c0 0f 84 2e 02 00 00 48 c7 c0 9c 1a 8b 8e
RSP: 0018:ffffc9000c8bf760 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff81680367
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e8ae5e8
RBP: ffffc9000c8bf878 R08: ffffffff8e8ae5ef R09: 1ffffffff1d15cbd
R10: dffffc0000000000 R11: fffffbfff1d15cbe R12: 1ffff92001917ef8
R13: ffff8880b8f3c298 R14: 0000000000000001 R15: dffffc0000000000
FS:  00007febe72756c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000180 CR3: 000000007b000000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 _raw_spin_lock_nested+0x32/0x50 kernel/locking/spinlock.c:378
 raw_spin_rq_lock_nested+0x29/0x130 kernel/sched/core.c:559
 raw_spin_rq_lock kernel/sched/sched.h:1379 [inline]
 rq_lock kernel/sched/sched.h:1688 [inline]
 __schedule+0x338/0x4660 kernel/sched/core.c:6614
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 futex_wait_queue+0x138/0x1b0 kernel/futex/waitwake.c:355
 futex_wait+0x1e9/0x5c0 kernel/futex/waitwake.c:656
 do_futex+0x2ff/0x3e0 kernel/futex/syscalls.c:134
 __do_sys_futex kernel/futex/syscalls.c:211 [inline]
 __se_sys_futex+0x3a9/0x440 kernel/futex/syscalls.c:192
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7febe639ce59
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:00007febe72750e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007febe6615fa8 RCX: 00007febe639ce59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007febe6615fa8
RBP: 00007febe6615fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007febe6616038 R14: 00007ffef979f170 R15: 00007ffef979f258
 </TASK>
sched: RT throttling activated

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/27 05:17 linux-6.6.y d1cfde2d5d15 fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2025/11/14 11:01 linux-6.6.y 0a805b6ea8cd 07e030de .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2025/09/06 16:10 linux-6.6.y 355bd0b51d2f d291dd2d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2026/08/02 15:07 linux-6.6.y a1153c0deb44 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2026/06/17 12:10 linux-6.6.y 924b4a879cbb 62cc6db3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2026/06/13 00:23 linux-6.6.y 924b4a879cbb 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2026/05/22 21:56 linux-6.6.y eac8889a3a1c 5f091fcc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2026/05/13 06:54 linux-6.6.y 3b9f64db0496 a0949470 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2026/05/10 12:13 linux-6.6.y 3b9f64db0496 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2025/11/25 06:21 linux-6.6.y 1e89a1be4fe9 64219f15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
2025/09/10 07:55 linux-6.6.y fe9731e10004 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_getpid
* Struck through repros no longer work on HEAD.