From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f72.google.com (mail-ot1-f72.google.com [209.85.210.72]) (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 4B75C33D4F5 for ; Mon, 12 Jan 2026 08:40:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768207207; cv=none; b=sCEA2rL35vnSEbP7j/ffZuMx6PqYRXPeUeu7BzVXERbJ9iIr+2XmCqqiAQT/n2EfnG7OXEX2QYiewvobI8ip2a+KJj5NP1j74CReEbYJVqz391vGpbTbsFF9w7p18H3gxRiYmsdU8UMjMnvKDo0oyTlMHODuywz32GdmXU6uDqg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768207207; c=relaxed/simple; bh=M3Yb8yveBMA3yjy6nLgs8onS4ypqOoE3v6az0GMEgvM=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:4ecf:b0:65f:fee:f7cc with SMTP id 006d021491bc7-65f54f52054mr6758542eaf.49.1768207205338; Mon, 12 Jan 2026 00:40:05 -0800 (PST) Date: Mon, 12 Jan 2026 00:40:05 -0800 In-Reply-To: <20260112075620.621464-1-kartikey406@gmail.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6964b365.050a0220.eaf7.008f.GAE@google.com> Subject: Re: [syzbot] [mm?] INFO: rcu detected stall in purge_vmap_node From: syzbot To: kartikey406@gmail.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: INFO: rcu detected stall in unwind_next_frame rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6892/1:b..l P6893/3:b..l P6746/1:b..l rcu: (detected by 1, t=10502 jiffies, g=16737, q=586 ncpus=2) task:kworker/u8:18 state:R running task stack:24088 pid:6746 tgid:6746 ppid:2 task_flags:0x4208060 flags:0x00080000 Workqueue: kvfree_rcu_reclaim kfree_rcu_monitor Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x1139/0x6150 kernel/sched/core.c:6863 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7190 irqentry_exit+0x1d8/0x8c0 kernel/entry/common.c:216 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:lock_acquire+0x62/0x330 kernel/locking/lockdep.c:5872 Code: b4 18 12 83 f8 07 0f 87 a2 02 00 00 89 c0 48 0f a3 05 e2 c1 ee 0e 0f 82 74 02 00 00 8b 35 7a f2 ee 0e 85 f6 0f 85 8d 00 00 00 <48> 8b 44 24 30 65 48 2b 05 f9 b3 18 12 0f 85 ad 02 00 00 48 83 c4 RSP: 0018:ffffc90003fbf5b8 EFLAGS: 00000206 RAX: 0000000000000046 RBX: ffffffff8e3c96a0 RCX: 00000000993b8195 RDX: 0000000000000000 RSI: ffffffff8daa8a1d RDI: ffffffff8bf2b400 RBP: 0000000000000002 R08: 00000000e61a05bb R09: 00000000be61a05b R10: 0000000000000002 R11: ffff888029058b30 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 rcu_lock_acquire include/linux/rcupdate.h:331 [inline] rcu_read_lock include/linux/rcupdate.h:867 [inline] class_rcu_constructor include/linux/rcupdate.h:1195 [inline] unwind_next_frame+0xd1/0x20b0 arch/x86/kernel/unwind_orc.c:495 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122 kasan_save_stack+0x33/0x60 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2540 [inline] slab_free_freelist_hook mm/slub.c:2569 [inline] slab_free_bulk mm/slub.c:6703 [inline] kmem_cache_free_bulk mm/slub.c:7390 [inline] kmem_cache_free_bulk+0x2bf/0x680 mm/slub.c:7369 kfree_bulk include/linux/slab.h:830 [inline] kvfree_rcu_bulk+0x1b7/0x1e0 mm/slab_common.c:1523 kvfree_rcu_drain_ready mm/slab_common.c:1728 [inline] kfree_rcu_monitor+0x1d0/0x2f0 mm/slab_common.c:1801 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257 process_scheduled_works kernel/workqueue.c:3340 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 task:sed state:R running task stack:25800 pid:6893 tgid:6893 ppid:6890 task_flags:0x400000 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x1139/0x6150 kernel/sched/core.c:6863 preempt_schedule_common+0x44/0xc0 kernel/sched/core.c:7047 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline] _raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:186 spin_unlock include/linux/spinlock.h:391 [inline] filemap_map_pages+0x1194/0x1e00 mm/filemap.c:3931 do_fault_around mm/memory.c:5713 [inline] do_read_fault mm/memory.c:5746 [inline] do_fault+0x9cd/0x1ad0 mm/memory.c:5889 do_pte_missing mm/memory.c:4401 [inline] handle_pte_fault mm/memory.c:6273 [inline] __handle_mm_fault+0x1919/0x2bb0 mm/memory.c:6411 handle_mm_fault+0x3fe/0xad0 mm/memory.c:6580 do_user_addr_fault+0x60c/0x1370 arch/x86/mm/fault.c:1336 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x64/0xc0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 RIP: 0033:0x7fc6d7657c50 RSP: 002b:00007ffe6008c528 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 00007fc6d768e490 RCX: 00007ffe6008c560 RDX: 00007fc6d7689d63 RSI: 00007fc6d7689d36 RDI: 00007ffe6008c748 RBP: 0000000000000041 R08: 00007ffe6008c550 R09: 00007ffe6008c558 R10: 0000000000000004 R11: 0000000000000246 R12: 00007ffe6008c748 R13: 00007ffe6008c550 R14: 00007fc6d76ce000 R15: 00005602504c1d98 task:udevd state:R running task stack:28152 pid:6892 tgid:6892 ppid:5186 task_flags:0x400140 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x1139/0x6150 kernel/sched/core.c:6863 preempt_schedule_common+0x44/0xc0 kernel/sched/core.c:7047 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] _raw_spin_unlock_irqrestore+0x61/0x80 kernel/locking/spinlock.c:194 sock_def_readable+0x15b/0x5d0 net/core/sock.c:3611 unix_dgram_sendmsg+0xcbd/0x1830 net/unix/af_unix.c:2286 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] sock_write_iter+0x566/0x610 net/socket.c:1195 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7d3/0x11d0 fs/read_write.c:686 ksys_write+0x1f8/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f6502bdf407 RSP: 002b:00007ffc4b535850 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f6502b53880 RCX: 00007f6502bdf407 RDX: 0000000000000000 RSI: 00007ffc4b5358f7 RDI: 000000000000000a RBP: 000000000000000a R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007f6502b536e8 R13: 0000000000000000 R14: 0000000000000000 R15: 000055685a0a1150 rcu: rcu_preempt kthread starved for 10572 jiffies! g16737 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:28120 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x1139/0x6150 kernel/sched/core.c:6863 __schedule_loop kernel/sched/core.c:6945 [inline] schedule+0xe7/0x3a0 kernel/sched/core.c:6960 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 rcu: Stack dump where RCU GP kthread last ran: Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82 Code: a6 5f 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 13 19 12 00 fb f4 cc 35 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 RSP: 0018:ffffffff8e007df8 EFLAGS: 000002c6 RAX: 0000000000186859 RBX: 0000000000000000 RCX: ffffffff8b7846d9 RDX: 0000000000000000 RSI: ffffffff8daceab2 RDI: ffffffff8bf2b400 RBP: fffffbfff1c12f68 R08: 0000000000000001 R09: ffffed101708673d R10: ffff8880b84339eb R11: ffffffff8e098670 R12: 0000000000000000 R13: ffffffff8e097b40 R14: ffffffff9088bdd0 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8881248f5000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055555eaef588 CR3: 00000000522b3000 CR4: 00000000003526f0 Call Trace: arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline] default_idle+0x13/0x20 arch/x86/kernel/process.c:767 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:191 [inline] do_idle+0x38d/0x510 kernel/sched/idle.c:332 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:430 rest_init+0x16b/0x2b0 init/main.c:757 start_kernel+0x3ef/0x4d0 init/main.c:1206 x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x130/0x190 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x148 Tested on: commit: 0f61b186 Linux 6.19-rc5 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1397199a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1859476832863c41 dashboard link: https://syzkaller.appspot.com/bug?extid=d8d4c31d40f868eaea30 compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=1704399a580000