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Message-ID: <687dab90.a70a0220.693ce.00dc.GAE@google.com> Date: Sun, 20 Jul 2025 19:53:04 -0700 From: syzbot <syzbot+5583f599fe40b819b3e7@...kaller.appspotmail.com> To: hdanton@...a.com, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com Subject: Re: [syzbot] [mm?] [input?] [usb?] INFO: rcu detected stall in devtmpfsd (3) Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: INFO: rcu detected stall in worker_thread rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P1583/2:b..l rcu: (detected by 0, t=10503 jiffies, g=17525, q=2531 ncpus=2) task:kworker/1:2 state:R running task stack:24872 pid:1583 tgid:1583 ppid:2 task_flags:0x4208060 flags:0x00004000 Workqueue: mld mld_ifc_work Call Trace: <TASK> context_switch kernel/sched/core.c:5397 [inline] __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7109 irqentry_exit+0x6f/0x90 kernel/entry/common.c:307 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:lock_acquire+0x175/0x360 kernel/locking/lockdep.c:5875 Code: 00 00 00 00 9c 8f 44 24 30 f7 44 24 30 00 02 00 00 0f 85 cd 00 00 00 f7 44 24 08 00 02 00 00 74 01 fb 65 48 8b 05 6b 44 02 11 <48> 3b 44 24 58 0f 85 f2 00 00 00 48 83 c4 60 5b 41 5c 41 5d 41 5e RSP: 0018:ffffc900053ef238 EFLAGS: 00000206 RAX: 00a7868fc370bc00 RBX: 0000000000000000 RCX: 00a7868fc370bc00 RDX: 0000000000000000 RSI: ffffffff8db87282 RDI: ffffffff8be29ec0 RBP: ffffffff8172aae5 R08: 0000000000000000 R09: ffffffff8172aae5 R10: ffffc900053ef3f8 R11: ffffffff81acfe40 R12: 0000000000000002 R13: ffffffff8e13f0e0 R14: 0000000000000000 R15: 0000000000000246 rcu_lock_acquire include/linux/rcupdate.h:331 [inline] rcu_read_lock include/linux/rcupdate.h:841 [inline] class_rcu_constructor include/linux/rcupdate.h:1155 [inline] unwind_next_frame+0xc2/0x2390 arch/x86/kernel/unwind_orc.c:479 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:68 unpoison_slab_object mm/kasan/common.c:319 [inline] __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:345 kasan_slab_alloc include/linux/kasan.h:250 [inline] slab_post_alloc_hook mm/slub.c:4148 [inline] slab_alloc_node mm/slub.c:4197 [inline] kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4204 dst_alloc+0x105/0x170 net/core/dst.c:89 ip6_dst_alloc net/ipv6/route.c:342 [inline] icmp6_dst_alloc+0x75/0x420 net/ipv6/route.c:3324 mld_sendpack+0x678/0xd80 net/ipv6/mcast.c:1857 mld_send_cr net/ipv6/mcast.c:2169 [inline] mld_ifc_work+0x835/0xde0 net/ipv6/mcast.c:2702 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> rcu: rcu_preempt kthread starved for 3495 jiffies! g17525 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:26792 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00004000 Call Trace: <TASK> context_switch kernel/sched/core.c:5397 [inline] __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786 __schedule_loop kernel/sched/core.c:6864 [inline] schedule+0x165/0x360 kernel/sched/core.c:6879 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2054 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2256 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> rcu: Stack dump where RCU GP kthread last ran: CPU: 0 UID: 0 PID: 6673 Comm: dhcpcd-run-hook Not tainted 6.16.0-rc7-syzkaller-g89be9a83ccf1 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 RIP: 0010:csd_lock_wait kernel/smp.c:340 [inline] RIP: 0010:smp_call_function_many_cond+0xf69/0x12d0 kernel/smp.c:885 Code: 00 45 8b 2f 44 89 ee 83 e6 01 31 ff e8 c0 78 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 6b 74 0b 00 eb 37 f3 90 <43> 0f b6 04 2c 84 c0 75 10 41 f7 07 01 00 00 00 74 1e e8 50 74 0b RSP: 0000:ffffc90003faf560 EFLAGS: 00000293 RAX: ffffffff81b4bcb0 RBX: ffff8880b863b1c0 RCX: ffff888026c01e00 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffc90003faf6c0 R08: ffffffff8fa1faf7 R09: 1ffffffff1f43f5e R10: dffffc0000000000 R11: fffffbfff1f43f5f R12: 1ffff110170e7f5d R13: dffffc0000000000 R14: 0000000000000001 R15: ffff8880b873fae8 FS: 00007f6e34ee0c80(0000) GS:ffff888125c18000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000c00202a000 CR3: 0000000029e28000 CR4: 00000000003526f0 Call Trace: <TASK> on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1052 __flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline] flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline] flush_tlb_mm_range+0x6b1/0x12c0 arch/x86/mm/tlb.c:1451 dup_mmap+0x15a0/0x1ac0 mm/mmap.c:1877 dup_mm kernel/fork.c:1477 [inline] copy_mm+0x13c/0x4b0 kernel/fork.c:1529 copy_process+0x16d3/0x3b80 kernel/fork.c:2169 kernel_clone+0x21e/0x870 kernel/fork.c:2599 __do_sys_clone kernel/fork.c:2742 [inline] __se_sys_clone kernel/fork.c:2726 [inline] __x64_sys_clone+0x18b/0x1e0 kernel/fork.c:2726 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f6e3507a636 Code: 89 df e8 6d e8 f6 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 52 89 c5 85 c0 75 31 64 48 8b 04 25 10 00 00 RSP: 002b:00007ffdd4454400 EFLAGS: 00000246 ORIG_RAX: 0000000000000038 RAX: ffffffffffffffda RBX: 00007ffdd4454408 RCX: 00007f6e3507a636 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011 RBP: 000055e0d3c6bc30 R08: 0000000000000000 R09: 0000000000000030 R10: 00007f6e34ee0f50 R11: 0000000000000246 R12: 000055e0d3c79290 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 </TASK> Tested on: commit: 89be9a83 Linux 6.16-rc7 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=16dc0fd4580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761 dashboard link: https://syzkaller.appspot.com/bug?extid=5583f599fe40b819b3e7 compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7 Note: no patches were applied.
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