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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: 63d, last: 1d12h
▶ ▼ 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 1108d 1175d 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 182d 351d 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 901d 901d 0/29 closed as invalid on 2024/02/12 15:20
upstream INFO: rcu detected stall in __unix_dgram_recvmsg (2) net 1 2 1009d 1013d 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: 	1-...0: (0 ticks this GP) idle=cd24/1/0x4000000000000000 softirq=45654/45654 fqs=1375
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:        0          0            0
rcu: 	cputime:        0          0            0   ==> 52550(ms)
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P10303/1:b..l P8038/1:b..l
rcu: 	(detected by 0, t=10506 jiffies, g=47105, q=88 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 11443 Comm: syz.3.1184 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4796 [inline]
RIP: 0010:__lock_acquire+0xa1c/0x7d40 kernel/locking/lockdep.c:5087
Code: 00 00 4c 89 f0 48 c1 e8 03 42 0f b6 04 00 84 c0 0f 85 37 01 00 00 41 80 3e 02 0f 84 91 00 00 00 48 8b 44 24 78 42 0f b6 04 00 <84> c0 0f 85 ef 00 00 00 48 ff c3 48 8b 44 24 40 48 63 00 49 83 c7
RSP: 0018:ffffc900001f08a0 EFLAGS: 00000093
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff911cd508
RBP: ffffc900001f0ae8 R08: dffffc0000000000 R09: 1ffffffff2239aa1
R10: dffffc0000000000 R11: fffffbfff2239aa2 R12: 0000000000000002
R13: ffff888029aa2928 R14: ffffffff90b3ab7a R15: ffff888029aa2928
FS:  00007f92b79d56c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f92b79d4ff8 CR3: 0000000025dd7000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
 debug_object_deactivate+0x67/0x390 lib/debugobjects.c:764
 debug_hrtimer_deactivate kernel/time/hrtimer.c:455 [inline]
 __run_hrtimer kernel/time/hrtimer.c:1722 [inline]
 __hrtimer_run_queues+0x2cb/0xc40 kernel/time/hrtimer.c:1818
 hrtimer_interrupt+0x3c9/0x9c0 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> 2b 88 ca f6 65 8b 05 bc b0 71 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc90004e8f580 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 88f1841dd49ccb00
RDX: dffffc0000000000 RSI: ffffffff8acacbe0 RDI: 0000000000000001
RBP: ffffc90004e8f610 R08: ffffffff911cd5af R09: 1ffffffff2239ab5
R10: dffffc0000000000 R11: fffffbfff2239ab6 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88801df4cec0 R15: 1ffff920009d1eb0
 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+0x4b8/0xd90 net/unix/af_unix.c:2439
 sock_recvmsg_nosec+0x82/0xd0 net/socket.c:1046
 ____sys_recvmsg+0x4e8/0x5e0 net/socket.c:2811
 ___sys_recvmsg+0x216/0x590 net/socket.c:2855
 do_recvmmsg+0x39a/0x870 net/socket.c:2949
 __sys_recvmmsg net/socket.c:3028 [inline]
 __do_sys_recvmmsg net/socket.c:3051 [inline]
 __se_sys_recvmmsg net/socket.c:3044 [inline]
 __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3044
 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: 0033:0x7f92b979ce59
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:00007f92b79d5028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f92b9a16090 RCX: 00007f92b979ce59
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000005
RBP: 00007f92b9832e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f92b9a16128 R14: 00007f92b9a16090 R15: 00007fff92bd69d8
 </TASK>
task:kworker/u4:22   state:R  running task     stack:22328 pid:8038  ppid:2      flags:0x00004000
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 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_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:692
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: 0000:ffffc9001a7e79c0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: a1189d8503b4f300
RDX: 0000000000000000 RSI: ffffffff8acadd60 RDI: ffffffff8b1c9c20
RBP: ffffc9001a7e7ad8 R08: dffffc0000000000 R09: 1ffffffff2239aa0
R10: dffffc0000000000 R11: fffffbfff2239aa1 R12: 1ffff920034fcf44
R13: ffffffff8d132160 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 batadv_nc_process_nc_paths+0xdb/0x390 net/batman-adv/network-coding.c:687
 batadv_nc_worker+0x52b/0x610 net/batman-adv/network-coding.c:735
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 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:syz-executor    state:R  running task     stack:21192 pid:10303 ppid:10292  flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 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 include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 copy_pte_range mm/memory.c:1107 [inline]
 copy_pmd_range mm/memory.c:1168 [inline]
 copy_pud_range mm/memory.c:1205 [inline]
 copy_p4d_range mm/memory.c:1229 [inline]
 copy_page_range+0x2ba0/0x3670 mm/memory.c:1323
 dup_mmap kernel/fork.c:769 [inline]
 dup_mm kernel/fork.c:1694 [inline]
 copy_mm+0x1281/0x1d80 kernel/fork.c:1743
 copy_process+0x16f7/0x3dc0 kernel/fork.c:2508
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2917
 __do_sys_clone kernel/fork.c:3060 [inline]
 __se_sys_clone kernel/fork.c:3044 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3044
 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: 0033:0x7f82175c58d2
RSP: 002b:00007ffde8670120 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffde8670120 RCX: 00007f82175c58d2
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffde86702ac R08: 0000000000000000 R09: 0000000000000001
R10: 000055557fb3c7d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 00000000000a9196 R15: 00007ffde8670300
 </TASK>
rcu: rcu_preempt kthread starved for 3630 jiffies! g47105 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:26184 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 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+0x313/0x1590 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: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: 88 1f 02 c3 cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d 43 e4 3f 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2e 41 89 de 80
RSP: 0018:ffffffff8ce07d80 EFLAGS: 000002c2
RAX: 1229dee6fd642800 RBX: ffffffff8162ae21 RCX: 1229dee6fd642800
RDX: 0000000000000001 RSI: ffffffff8acacbe0 RDI: ffffffff8b1c9c20
RBP: ffffffff8ce07eb8 R08: ffff8880b8e36bab R09: 1ffff110171c6d75
R10: dffffc0000000000 R11: ffffed10171c6d76 R12: 1ffffffff19c0fbc
R13: dffffc0000000000 R14: 1ffffffff19d2688 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7441e63521 CR3: 000000002f885000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:178 [inline]
 do_idle+0x221/0x590 kernel/sched/idle.c:302
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:401
 rest_init+0x2e2/0x300 init/main.c:744
 arch_call_rest_init+0xe/0x10 init/main.c:840
 start_kernel+0x459/0x4e0 init/main.c:1085
 x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
 x86_64_start_kernel+0x60/0x60 arch/x86/kernel/head64.c:536
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.