From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-21.mta0.migadu.com [91.218.175.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0F1DB311C36 for ; Fri, 21 Aug 2026 01:06:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.21 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787274419; cv=none; b=LUR6ooEcAKeDkYKrrJfcC4oQV5Eo2Or15Qpu80Y6l5IuZojP32Zyd3b0Dnmv77WEhDyKaVoBgngCIUtC88RJarobpBwF/5IeO6EM0sOPqCJL2LHmGvMfxG2KPOS/JZo4Vy0uHQBF3SkJl4LLRPPtlQk7+opv0IY688bS7Fl/x/k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787274419; c=relaxed/simple; bh=K1iqVU8GuphpTpCTo1BVQZqa9SDJDP7wQUwvLAGhYkA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hFpaZ5czLuPFwlbbNvmNy7N3rBjKcmJWchcNNkWx4PjQaZqyNC42HWr+Zl54a/Qhk5f3FU9L4EjLJhy7XPGt/g7+Cux1lhxoZG985Z2ggNLkdwqyVc2pYJj7g9do0jYR3yIY9cdbJ1lKt4dHyzbxCPAhus81zQ44NtPW8Sx740s= ARC-Authentication-Results:i=1; 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Fri, 21 Aug 2026 01:06:54 +0000 X-Mizu-Trace-ID: 89f7e09dcf9bdac5 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Fri, 21 Aug 2026 09:06:48 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] INFO: rcu detected stall in kvm_vm_release (4) To: Andrew Morton , syzbot Cc: brendan.jackman@linux.dev, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, surenb@google.com, syzkaller-bugs@googlegroups.com, vbabka@kernel.org, ziy@nvidia.com, Zhen Ni , Oscar Salvador , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov References: <6a86fe29.f7a79266.2f965f.004a.GAE@google.com> <20260820092904.7a2b43fff85ed0c13b9c74ab@linux-foundation.org> Content-Language: en-US From: Ye Liu In-Reply-To: <20260820092904.7a2b43fff85ed0c13b9c74ab@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 在 2026/8/21 00:29, Andrew Morton 写道: > On Thu, 20 Aug 2026 06:16:25 -0700 syzbot wrote: > >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: e8bf40d15402 Merge tag 'chrome-platform-firmware-v7.3' of .. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=1434f815580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=1941312e3e971b07 >> dashboard link: https://syzkaller.appspot.com/bug?extid=5f0b6e2e4195c75b5658 >> compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/7df7b958efe0/disk-e8bf40d1.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/cefbf90e524a/vmlinux-e8bf40d1.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/37a530b91001/bzImage-e8bf40d1.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+5f0b6e2e4195c75b5658@syzkaller.appspotmail.com >> >> rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: >> rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P21500/1:b..l >> rcu: (detected by 0, t=10503 jiffies, g=207513, q=1145 ncpus=2) >> task:syz.9.4605 state:R running task stack:26920 pid:21500 tgid:21500 ppid:14397 task_flags:0x40044c flags:0x00080003 > > Thanks. > > lazybutt pasted this into Gemini: > https://share.gemini.google/9rAubqC4qNzf > > : The combination of debug tools: KASAN quarantine processing + ORC > : unwinder + page_owner stack tracing executed so slowly on the CPU that > : it exceeded the RCU stall threshold. > > (I think we've recently seen the same thing, different callers) > > I can't say I'm terribly motivated. page_owner is expensive and if you > run heavy stress testing with page_owner enabled then such things > aren't surprising. > > Let me Cc a few page_owner and KASAN people, see if they feel > differently. Adding cond_resched() to the qlist_free_all() loop would fix this . kasan_quarantine_remove_cache() already dose the same in its scanning loop. > >> Call Trace: >> >> context_switch kernel/sched/core.c:5510 [inline] >> __schedule+0x17d4/0x5630 kernel/sched/core.c:7239 >> preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7561 >> irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline] >> irqentry_exit+0x14f/0x910 kernel/entry/common.c:167 >> asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 >> RIP: 0010:lock_acquire+0x222/0x350 kernel/locking/lockdep.c:5890 >> Code: ff ff ff e8 c0 0b 32 0a f7 44 24 08 00 02 00 00 0f 84 39 ff ff ff 65 48 8b 05 12 77 cb 11 48 3b 44 24 58 75 33 fb 48 83 c4 60 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d 57 a1 b8 >> RSP: 0018:ffffc900074cf260 EFLAGS: 00000286 >> RAX: 7db047bb98fc4c00 RBX: 0000000000000000 RCX: 0000000000000046 >> RDX: 00000000c0065176 RSI: ffffffff8e4b5735 RDI: ffffffff8c4bdd80 >> RBP: ffffffff8177710f R08: ffffffff8177710f R09: 0000000000000000 >> R10: 0000000000000000 R11: ffffffff8eb5a0e0 R12: 0000000000000002 >> R13: ffffffff8eb5a0e0 R14: 0000000000000000 R15: 0000000000000246 >> rcu_lock_acquire include/linux/rcupdate.h:300 [inline] >> rcu_read_lock include/linux/rcupdate.h:840 [inline] >> class_rcu_constructor include/linux/rcupdate.h:1183 [inline] >> unwind_next_frame+0xac/0x2550 arch/x86/kernel/unwind_orc.c:495 >> arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25 >> stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 >> save_stack+0x122/0x230 mm/page_owner.c:165 >> __reset_page_owner+0x71/0x1f0 mm/page_owner.c:320 >> reset_page_owner include/linux/page_owner.h:25 [inline] >> __free_pages_prepare mm/page_alloc.c:1406 [inline] >> __free_frozen_pages+0xc22/0xd20 mm/page_alloc.c:2950 >> __slab_free+0x274/0x2c0 mm/slub.c:5741 >> qlink_free mm/kasan/quarantine.c:163 [inline] >> qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179 >> kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286 >> __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350 >> kasan_slab_alloc include/linux/kasan.h:253 [inline] >> slab_post_alloc_hook mm/slub.c:4584 [inline] >> slab_alloc_node mm/slub.c:4917 [inline] >> __do_kmalloc_node mm/slub.c:5333 [inline] >> __kmalloc_noprof+0x315/0x720 mm/slub.c:5359 >> _kmalloc_noprof include/linux/slab.h:992 [inline] >> _kzalloc_noprof include/linux/slab.h:1309 [inline] >> kobject_get_path+0xc5/0x2f0 lib/kobject.c:161 >> kobject_uevent_env+0x29e/0x9e0 lib/kobject_uevent.c:548 >> kvm_uevent_notify_change+0x300/0x3a0 virt/kvm/kvm_main.c:6335 >> kvm_destroy_vm virt/kvm/kvm_main.c:1260 [inline] >> kvm_put_kvm+0xa9/0xb50 virt/kvm/kvm_main.c:1331 >> kvm_vm_release+0x43/0x50 virt/kvm/kvm_main.c:1354 >> __fput+0x418/0xa50 fs/file_table.c:512 >> task_work_run+0x1d9/0x270 kernel/task_work.c:233 >> exit_task_work include/linux/task_work.h:40 [inline] >> do_exit+0x73a/0x2360 kernel/exit.c:1009 >> do_group_exit+0x22d/0x2f0 kernel/exit.c:1152 >> get_signal+0x121b/0x12c0 kernel/signal.c:3046 >> arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337 >> __exit_to_user_mode_loop kernel/entry/common.c:66 [inline] >> exit_to_user_mode_loop+0x10e/0x770 kernel/entry/common.c:101 >> __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] >> syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] >> syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline] >> do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7fe3a1f5e90e >> RSP: 002b:00007fe3a2e23f58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e6 >> RAX: fffffffffffffdfc RBX: 00007fe3a2e246c0 RCX: 00007fe3a1f5e90e >> RDX: 00007fe3a2e23fb0 RSI: 0000000000000000 RDI: 0000000000000000 >> RBP: 00007fe3a2035024 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 >> R13: 00007fe3a2226308 R14: 00007fe3a2226270 R15: 00007fe3a234fa48 >> >> >> >> --- >> This report is generated by a bot. It may contain errors. >> See https://goo.gl/tpsmEJ for more information about syzbot. >> syzbot engineers can be reached at syzkaller@googlegroups.com. >> >> syzbot will keep track of this issue. See: >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot. >> >> If the report is already addressed, let syzbot know by replying with: >> #syz fix: exact-commit-title >> >> If you want to overwrite report's subsystems, reply with: >> #syz set subsystems: new-subsystem >> (See the list of subsystem names on the web dashboard) >> >> If the report is a duplicate of another one, reply with: >> #syz dup: exact-subject-of-another-report >> >> If you want to undo deduplication, reply with: >> #syz undup -- Thanks, Ye Liu