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rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P9721 (detected by 0, t=10502 jiffies, g=43005, q=231 ncpus=2) task:syz.2.1941 state:R running task stack:25712 pid:9721 ppid:4271 flags:0x00004008 Call Trace: <IRQ> sched_show_task+0x497/0x5b0 kernel/sched/core.c:8954 rcu_print_detail_task_stall_rnp kernel/rcu/tree_stall.h:261 [inline] print_other_cpu_stall+0x10a9/0x1430 kernel/rcu/tree_stall.h:606 check_cpu_stall kernel/rcu/tree_stall.h:778 [inline] rcu_pending kernel/rcu/tree.c:3895 [inline] rcu_sched_clock_irq+0x88a/0x1230 kernel/rcu/tree.c:2394 update_process_times+0x143/0x1b0 kernel/time/timer.c:2072 tick_sched_handle kernel/time/tick-sched.c:254 [inline] tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1501 __run_hrtimer kernel/time/hrtimer.c:1747 [inline] __hrtimer_run_queues+0x50b/0xd50 kernel/time/hrtimer.c:1811 hrtimer_interrupt+0x3c5/0x9c0 kernel/time/hrtimer.c:1873 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline] __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline] sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691 RIP: 0010:kasan_quarantine_put+0x84/0x220 mm/kasan/quarantine.c:245 Code: e8 71 54 b5 ff 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 0f 85 83 00 00 00 41 f7 c7 00 02 00 00 74 01 fb 31 c0 <48> 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f c3 48 8d 80 00 67 03 00 45 RSP: 0018:ffffc900000079a8 EFLAGS: 00000206 RAX: e2aa9a5f86249201 RBX: ffff888034099800 RCX: e2aa9a5f86249200 RDX: dffffc0000000000 RSI: ffffffff8a8c1120 RDI: ffffffff8adf13a0 RBP: ffff888034099800 R08: ffffffff90af92ff R09: 1ffffffff215f25f R10: dffffc0000000000 R11: fffffbfff215f260 R12: 0000000000000000 R13: ffffc90000007a40 R14: 00000000000b6f00 R15: 0000000000000286 kasan_slab_free include/linux/kasan.h:177 [inline] slab_free_hook mm/slub.c:1729 [inline] slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755 slab_free mm/slub.c:3687 [inline] __kmem_cache_free+0xb6/0x1f0 mm/slub.c:3700 skb_free_head net/core/skbuff.c:762 [inline] skb_release_data+0x5db/0x7c0 net/core/skbuff.c:791 skb_release_all net/core/skbuff.c:856 [inline] __kfree_skb+0x4c/0x60 net/core/skbuff.c:870 tcp_write_queue_purge+0x13f/0x2f0 net/ipv4/tcp.c:3123 tcp_done_with_error+0x3f/0xc0 net/ipv4/tcp_input.c:4408 tcp_write_err net/ipv4/tcp_timer.c:70 [inline] tcp_write_timeout net/ipv4/tcp_timer.c:273 [inline] tcp_retransmit_timer+0x1270/0x2790 net/ipv4/tcp_timer.c:547 tcp_write_timer+0x126/0x280 net/ipv4/tcp_timer.c:676 call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701 expire_timers kernel/time/timer.c:1752 [inline] __run_timers+0x53e/0x800 kernel/time/timer.c:2023 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036 handle_softirqs+0x2a1/0x930 kernel/softirq.c:596 do_softirq+0x142/0x210 kernel/softirq.c:497 </IRQ> <TASK> __local_bh_enable_ip+0x180/0x1c0 kernel/softirq.c:421 local_bh_enable include/linux/bottom_half.h:33 [inline] xdp_test_run_batch net/bpf/test_run.c:340 [inline] bpf_test_run_xdp_live+0x1834/0x1a90 net/bpf/test_run.c:362 bpf_prog_test_run_xdp+0x736/0xf10 net/bpf/test_run.c:1412 bpf_prog_test_run+0x31e/0x390 kernel/bpf/syscall.c:3695 __sys_bpf+0x62b/0x780 kernel/bpf/syscall.c:5049 __do_sys_bpf kernel/bpf/syscall.c:5135 [inline] __se_sys_bpf kernel/bpf/syscall.c:5133 [inline] __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5133 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f61ba99c819 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:00007f61bb8e3028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007f61bac15fa0 RCX: 00007f61ba99c819 RDX: 0000000000000050 RSI: 0000200000000600 RDI: 000000000000000a RBP: 00007f61baa32c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f61bac16038 R14: 00007f61bac15fa0 R15: 00007ffd65bc6238 </TASK> rcu: rcu_preempt kthread starved for 10517 jiffies! g43005 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:27184 pid:16 ppid:2 flags:0x00004000 Call Trace: <TASK> context_switch kernel/sched/core.c:5245 [inline] __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562 schedule+0xb9/0x180 kernel/sched/core.c:6638 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168 rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> rcu: Stack dump where RCU GP kthread last ran: CPU: 0 PID: 9721 Comm: syz.2.1941 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 RIP: 0010:kasan_quarantine_put+0x84/0x220 mm/kasan/quarantine.c:245 Code: e8 71 54 b5 ff 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 0f 85 83 00 00 00 41 f7 c7 00 02 00 00 74 01 fb 31 c0 <48> 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f c3 48 8d 80 00 67 03 00 45 RSP: 0018:ffffc900000079a8 EFLAGS: 00000206 RAX: e2aa9a5f86249201 RBX: ffff888034099800 RCX: e2aa9a5f86249200 RDX: dffffc0000000000 RSI: ffffffff8a8c1120 RDI: ffffffff8adf13a0 RBP: ffff888034099800 R08: ffffffff90af92ff R09: 1ffffffff215f25f R10: dffffc0000000000 R11: fffffbfff215f260 R12: 0000000000000000 R13: ffffc90000007a40 R14: 00000000000b6f00 R15: 0000000000000286 FS: 00007f61bb8e36c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc03cff0ffc CR3: 000000002e22b000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: <IRQ> kasan_slab_free include/linux/kasan.h:177 [inline] slab_free_hook mm/slub.c:1729 [inline] slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755 slab_free mm/slub.c:3687 [inline] __kmem_cache_free+0xb6/0x1f0 mm/slub.c:3700 skb_free_head net/core/skbuff.c:762 [inline] skb_release_data+0x5db/0x7c0 net/core/skbuff.c:791 skb_release_all net/core/skbuff.c:856 [inline] __kfree_skb+0x4c/0x60 net/core/skbuff.c:870 tcp_write_queue_purge+0x13f/0x2f0 net/ipv4/tcp.c:3123 tcp_done_with_error+0x3f/0xc0 net/ipv4/tcp_input.c:4408 tcp_write_err net/ipv4/tcp_timer.c:70 [inline] tcp_write_timeout net/ipv4/tcp_timer.c:273 [inline] tcp_retransmit_timer+0x1270/0x2790 net/ipv4/tcp_timer.c:547 tcp_write_timer+0x126/0x280 net/ipv4/tcp_timer.c:676 call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701 expire_timers kernel/time/timer.c:1752 [inline] __run_timers+0x53e/0x800 kernel/time/timer.c:2023 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036 handle_softirqs+0x2a1/0x930 kernel/softirq.c:596 do_softirq+0x142/0x210 kernel/softirq.c:497 </IRQ> <TASK> __local_bh_enable_ip+0x180/0x1c0 kernel/softirq.c:421 local_bh_enable include/linux/bottom_half.h:33 [inline] xdp_test_run_batch net/bpf/test_run.c:340 [inline] bpf_test_run_xdp_live+0x1834/0x1a90 net/bpf/test_run.c:362 bpf_prog_test_run_xdp+0x736/0xf10 net/bpf/test_run.c:1412 bpf_prog_test_run+0x31e/0x390 kernel/bpf/syscall.c:3695 __sys_bpf+0x62b/0x780 kernel/bpf/syscall.c:5049 __do_sys_bpf kernel/bpf/syscall.c:5135 [inline] __se_sys_bpf kernel/bpf/syscall.c:5133 [inline] __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5133 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f61ba99c819 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:00007f61bb8e3028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007f61bac15fa0 RCX: 00007f61ba99c819 RDX: 0000000000000050 RSI: 0000200000000600 RDI: 000000000000000a RBP: 00007f61baa32c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f61bac16038 R14: 00007f61bac15fa0 R15: 00007ffd65bc6238 </TASK>
| Time | Kernel | Commit | Syzkaller | Config | Log | Report | Syz repro | C repro | VM info | Assets (help?) | Manager | Title |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026/04/23 01:41 | linux-6.1.y | 7c87defbd336 | b10da5ec | .config | console log | report | info | [disk image] [vmlinux] [kernel image] | ci2-linux-6-1-kasan-perf | INFO: rcu detected stall in tcp_write_timer | ||
| 2026/03/06 03:15 | linux-6.1.y | f2ddafa93a25 | 31e9c887 | .config | console log | report | info | [disk image] [vmlinux] [kernel image] | ci2-linux-6-1-kasan-perf | INFO: rcu detected stall in tcp_write_timer |