INFO: rcu detected stall in __unix_dgram_recvmsg (2)

Status: upstream: reported on 2026/04/17 08:34
Reported-by: syzbot+d01746b561934d3e1617@syzkaller.appspotmail.com
First crash: 131d, last: 49d
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in __unix_dgram_recvmsg net 1 3 1175d 1242d 0/29 auto-obsoleted due to no activity on 2023/09/05 23:13
linux-6.6 INFO: rcu detected stall in __unix_dgram_recvmsg 1 6 249d 419d 0/2 auto-obsoleted due to no activity on 2026/03/30 01:03
upstream INFO: rcu detected stall in __unix_dgram_recvmsg (3) net 1 1 968d 968d 0/29 closed as invalid on 2024/02/12 15:20
upstream INFO: rcu detected stall in __unix_dgram_recvmsg (2) net 1 2 1076d 1080d 0/29 auto-obsoleted due to no activity on 2023/12/13 22:00

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (3 ticks this GP) idle=3d7c/1/0x4000000000000000 softirq=35705/35705 fqs=2
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P7036/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=50421, q=18 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 11074 Comm: syz.5.1362 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__raw_callee_save___pv_queued_spin_unlock+0x5/0x16
Code: 51 41 52 41 53 e8 8b 08 00 00 41 5b 41 5a 41 59 41 58 5f 5e 5a 59 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 52 <b8> 01 00 00 00 31 d2 f0 0f b0 17 3c 01 75 02 5a c3 56 0f b6 f0 e8
RSP: 0018:ffffc90000007c78 EFLAGS: 00000086
RAX: 1ffffffff19f3e30 RBX: ffff8880b8e2b740 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8880b8e2b740
RBP: 1ffff110171c56e9 R08: ffff8880b8e2b743 R09: 1ffff110171c56e8
R10: dffffc0000000000 R11: ffffed10171c56e9 R12: dffffc0000000000
R13: 1ffff110171c56ea R14: ffff8880b8e2b750 R15: ffff8880b8e2b748
FS:  00007f7a4ca8e6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2de1aff8 CR3: 0000000050d67000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 pv_queued_spin_unlock arch/x86/include/asm/paravirt.h:591 [inline]
 queued_spin_unlock arch/x86/include/asm/qspinlock.h:57 [inline]
 do_raw_spin_unlock+0x121/0x230 kernel/locking/spinlock_debug.c:141
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:150 [inline]
 _raw_spin_unlock_irqrestore+0x79/0x120 kernel/locking/spinlock.c:194
 __run_hrtimer kernel/time/hrtimer.c:1750 [inline]
 __hrtimer_run_queues+0x426/0xc10 kernel/time/hrtimer.c:1818
 hrtimer_interrupt+0x39d/0x980 kernel/time/hrtimer.c:1880
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xc0/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 9b ed c6 f6 65 8b 05 6c 3c 6e 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000dfcf580 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: ede2962bd9245900
RDX: dffffc0000000000 RSI: ffffffff8acacb60 RDI: 0000000000000001
RBP: ffffc9000dfcf610 R08: ffffffff911e75af R09: 1ffffffff223ceb5
R10: dffffc0000000000 R11: fffffbfff223ceb6 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88807d724ec0 R15: 1ffff92001bf9eb0
 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
 __unix_dgram_recvmsg+0x4bb/0xd90 net/unix/af_unix.c:2439
 sock_recvmsg_nosec+0x82/0xd0 net/socket.c:1047
 ____sys_recvmsg+0x4d7/0x5d0 net/socket.c:2812
 ___sys_recvmsg+0x214/0x590 net/socket.c:2856
 do_recvmmsg+0x377/0x810 net/socket.c:2950
 __sys_recvmmsg net/socket.c:3029 [inline]
 __do_sys_recvmmsg net/socket.c:3052 [inline]
 __se_sys_recvmmsg net/socket.c:3045 [inline]
 __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3045
 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: 0033:0x7f7a4bb9de59
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:00007f7a4ca8e028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f7a4be26090 RCX: 00007f7a4bb9de59
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007f7a4bc33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a4be26128 R14: 00007f7a4be26090 R15: 00007fff906cae28
 </TASK>
task:kworker/u4:19   state:R  running task     stack:22408 pid:7036  ppid:2      flags:0x00004000
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_notrace+0xdd/0x110 kernel/sched/core.c:6960
 preempt_schedule_notrace_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:46
 rcu_is_watching+0x7a/0xb0 kernel/rcu/tree.c:701
 trace_lock_acquire include/trace/events/lock.h:24 [inline]
 lock_acquire+0xc6/0x420 kernel/locking/lockdep.c:5725
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
 batadv_nc_worker+0xef/0x600 net/batman-adv/network-coding.c:719
 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>
rcu: rcu_preempt kthread starved for 10497 jiffies! g50421 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:27592 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
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 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:
CPU: 1 PID: 11 Comm: kworker/u4:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x10/0x60 kernel/kcov.c:216
Code: 89 fb e8 13 00 00 00 48 8b 3d ec 87 05 0d 48 89 de 5b e9 23 a7 57 00 cc cc cc f3 0f 1e fa 48 8b 04 24 65 48 8b 0d c0 d2 7c 7e <65> 8b 15 c1 d2 7c 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75
RSP: 0018:ffffc90000107778 EFLAGS: 00000202
RAX: ffffffff817bf7fd RBX: 1ffff110171c87a9 RCX: ffff88801b27bc00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000107900 R08: ffffffff911e7507 R09: 1ffffffff223cea0
R10: dffffc0000000000 R11: fffffbfff223cea1 R12: ffff8880b8e43d48
R13: ffff8880b8f3d3c0 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7a4bbeb540 CR3: 000000000cf32000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 csd_lock_wait kernel/smp.c:311 [inline]
 smp_call_function_many_cond+0xd9d/0x1190 kernel/smp.c:855
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
 text_poke_bp_batch+0x31e/0x980 arch/x86/kernel/alternative.c:2432
 text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x123/0x240 kernel/jump_label.c:207
 static_key_enable+0x1a/0x20 kernel/jump_label.c:220
 toggle_allocation_gate+0xa8/0x260 mm/kfence/core.c:847
 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>

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/07 18:50 linux-6.6.y da47cbc25466 76cdc0c0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/07/02 20:10 linux-6.6.y d1cfde2d5d15 2b70b115 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/07/01 06:00 linux-6.6.y d1cfde2d5d15 00a5cf1c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/30 17:57 linux-6.6.y d1cfde2d5d15 00e8b0fd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/29 15:23 linux-6.6.y d1cfde2d5d15 6a0c72dc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/26 19:32 linux-6.6.y d1cfde2d5d15 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/24 18:19 linux-6.6.y d1cfde2d5d15 302586aa .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/06/18 18:54 linux-6.6.y 924b4a879cbb a776b0d0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/05/07 21:55 linux-6.6.y 258cf62a6dfd cbf9e0fc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/04/20 23:46 linux-6.6.y 9760bf04666d e65da4ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
2026/04/17 08:33 linux-6.6.y 8cee53b8eaeb de0a551d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in __unix_dgram_recvmsg
* Struck through repros no longer work on HEAD.