INFO: rcu detected stall in sys_recvmmsg (2)

Status: upstream: reported on 2026/07/04 16:20
Reported-by: syzbot+25d1df4a916d933062cf@syzkaller.appspotmail.com
First crash: 26d, last: 1d14h
▶ ▼ Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_recvmmsg (3) prio:low net 1 283 10h13m 955d 0/29 upstream: reported on 2023/12/19 09:31
linux-6.1 INFO: rcu detected stall in sys_recvmmsg (3) 1 16 217d 612d 0/3 auto-obsoleted due to no activity on 2026/04/05 10:37
linux-4.19 INFO: rcu detected stall in sys_recvmmsg 1 syz, C error 1 1316d 1316d 0/1 upstream: reported C repro on 2022/12/23 04:58
linux-5.15 INFO: rcu detected stall in sys_recvmmsg missing-backport origin:upstream 1 syz, C done 82 2d05h 1212d 0/3 upstream: reported C repro on 2023/04/06 01:32
linux-6.1 INFO: rcu detected stall in sys_recvmmsg (4) 1 3 5d23h 99d 0/3 upstream: reported on 2026/04/22 14:30
linux-6.6 INFO: rcu detected stall in sys_recvmmsg 1 8 150d 378d 0/2 auto-obsoleted due to no activity on 2026/06/11 04:39
linux-6.1 INFO: rcu detected stall in sys_recvmmsg (2) 1 5 715d 847d 0/3 auto-obsoleted due to no activity on 2024/11/22 11:58
upstream INFO: rcu detected stall in sys_recvmmsg mptcp 1 syz, C done 52 1642d 1773d 20/29 fixed on 2022/03/08 16:11
linux-6.1 INFO: rcu detected stall in sys_recvmmsg 1 5 1093d 1224d 0/3 auto-obsoleted due to no activity on 2023/11/11 06:06
upstream INFO: rcu detected stall in sys_recvmmsg (2) net 1 4 1402d 1433d 0/29 auto-obsoleted due to no activity on 2023/01/03 09:53
android-5-15 BUG: soft lockup in sys_recvmmsg 1 5 736d 828d 0/2 auto-obsoleted due to no activity on 2024/10/23 09:30

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=0bf4/1/0x4000000000000000 softirq=46554/46557 fqs=1
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P13314/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=52001, q=55 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 13319 Comm: syz.1.1674 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:hlock_class kernel/locking/lockdep.c:228 [inline]
RIP: 0010:__lock_acquire+0x107f/0x7d80 kernel/locking/lockdep.c:5133
Code: 03 89 c3 81 e3 ff 1f 00 00 c1 e8 03 25 f8 03 00 00 48 8d b8 00 b5 1e 91 be 08 00 00 00 e8 09 59 77 00 48 0f a3 1d 11 1a b6 0f <0f> 83 48 01 00 00 48 69 c3 d0 00 00 00 48 8d 98 c0 33 b5 90 49 b8
RSP: 0018:ffffc900001f0880 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000068 RCX: ffffffff81689ae7
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff911eb508
RBP: ffffc900001f0ac8 R08: ffffffff911eb50f R09: 1ffffffff223d6a1
R10: dffffc0000000000 R11: fffffbfff223d6a2 R12: 0000000041359547
R13: ffff88802b638000 R14: 0000000041f79c6b R15: ffff88802b638b28
FS:  00007f41af4bf6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd1251eb680 CR3: 000000002e991000 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_activate+0x6c/0x500 lib/debugobjects.c:747
 debug_hrtimer_activate kernel/time/hrtimer.c:450 [inline]
 debug_activate kernel/time/hrtimer.c:504 [inline]
 enqueue_hrtimer+0x34/0x380 kernel/time/hrtimer.c:1100
 __run_hrtimer kernel/time/hrtimer.c:1771 [inline]
 __hrtimer_run_queues+0x62f/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:___sys_recvmsg+0x57/0x590 net/socket.c:2846
Code: 48 89 7c 24 38 65 48 8b 04 25 28 00 00 00 48 89 84 24 a0 01 00 00 48 b9 f8 f8 f8 f8 f8 f8 f8 f8 49 bf 00 00 00 00 00 fc ff df <4c> 8d ac 24 c0 00 00 00 4c 8d a4 24 60 01 00 00 48 c7 44 24 40 b3
RSP: 0018:ffffc9000cad7a80 EFLAGS: 00000282
RAX: 7af16665f5ac9000 RBX: 0000000000000002 RCX: f8f8f8f8f8f8f8f8
RDX: ffffc9000cad7d20 RSI: 00002000000c88c0 RDI: ffff88807864e000
RBP: ffffc9000cad7c70 R08: 0000000000003220 R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: 00002000000000c0
R13: 0000000000000008 R14: 00002000000c88c0 R15: dffffc0000000000
 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: 0033:0x7f41ae59df99
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:00007f41af4bf028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f41ae826090 RCX: 00007f41ae59df99
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007f41ae634ec4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f41ae826128 R14: 00007f41ae826090 R15: 00007ffc55ebcd68
 </TASK>
task:syz.3.1673      state:R  running task     stack:26792 pid:13314 ppid:5780   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6868
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6892
 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]
 zap_pte_range mm/memory.c:1523 [inline]
 zap_pmd_range mm/memory.c:1571 [inline]
 zap_pud_range mm/memory.c:1600 [inline]
 zap_p4d_range mm/memory.c:1621 [inline]
 unmap_page_range+0x2577/0x32f0 mm/memory.c:1642
 unmap_vmas+0x286/0x3f0 mm/memory.c:1732
 exit_mmap+0x238/0xb90 mm/mmap.c:3302
 __mmput+0x118/0x3a0 kernel/fork.c:1362
 exit_mm+0x23f/0x340 kernel/exit.c:570
 do_exit+0x909/0x2530 kernel/exit.c:871
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1026
 get_signal+0x12a6/0x1390 kernel/signal.c:2903
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdad939df99
RSP: 002b:00007fdada1c70e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fdad9626188 RCX: 00007fdad939df99
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fdad9626188
RBP: 00007fdad9626180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdad9626218 R14: 00007ffc6a830720 R15: 00007ffc6a830808
 </TASK>
rcu: rcu_preempt kthread starved for 10500 jiffies! g52001 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:27848 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 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: 0 PID: 12618 Comm: kworker/u4:18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xd85/0x1190 kernel/smp.c:855
Code: 45 8b 34 24 44 89 f6 83 e6 01 31 ff e8 14 fe 0a 00 41 83 e6 01 49 be 00 00 00 00 00 fc ff df 75 07 e8 4f fa 0a 00 eb 38 f3 90 <42> 0f b6 04 33 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 33 fa
RSP: 0018:ffffc900039e7780 EFLAGS: 00000293
RAX: ffffffff817c7aad RBX: 1ffff110171e82bd RCX: ffff888023babc00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900039e7900 R08: ffffffff911eb507 R09: 1ffffffff223d6a0
R10: dffffc0000000000 R11: fffffbfff223d6a1 R12: ffff8880b8f415e8
R13: ffff8880b8e3d3c0 R14: dffffc0000000000 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f41ae5eb680 CR3: 000000000cf32000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 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 (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/29 21:32 linux-6.6.y ae068b676196 6ef5c1e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_recvmmsg
2026/07/11 05:55 linux-6.6.y da47cbc25466 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_recvmmsg
2026/07/04 16:19 linux-6.6.y da47cbc25466 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_recvmmsg
* Struck through repros no longer work on HEAD.