From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D3B922FDE4 for ; Wed, 26 Feb 2025 07:03:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.191 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740553419; cv=none; b=sFLEIwUqjmFet3582oMXe5Zk8gueNlAjFsL5i73D1Ry6RaFX4qwBEkd0Zxg8edh75jHOH/YIyIsQW8Wg7ztvl86vI1R+zCmRXVSBbjyQ7iqCuI6hcvZjvA3tD4rpY0SX7mZqpYlqS7mGuDkBi1drT1Tbo+jCeV+qUcneaV/WaL8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740553419; c=relaxed/simple; bh=gXyhxY0ezuQp00101R1rDD6B+63lkwo6g0egIfxSXso=; h=To:From:Subject:CC:Message-ID:Date:MIME-Version:Content-Type; b=fguv5ACmOsAZ0C5AzLMrphFqRBY2LKSj54IMa+Kv6cKRwxEU2AzsGI0LQvp2oa5Zps8nuMreBjuSOcY3UZzupD1LCEXPZz0Eh7H/DC8TH69aUI7ptHF3pePW3KhX660CVjPvOaHeDjkja1H0skzF7fzG62URD+ZKYMaHsVRYMGk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.191 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.17]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4Z2lhJ5sw6z1ltY8; Wed, 26 Feb 2025 14:59:28 +0800 (CST) Received: from kwepemg200013.china.huawei.com (unknown [7.202.181.64]) by mail.maildlp.com (Postfix) with ESMTPS id 271541A0188; Wed, 26 Feb 2025 15:03:32 +0800 (CST) Received: from [10.174.179.24] (10.174.179.24) by kwepemg200013.china.huawei.com (7.202.181.64) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 26 Feb 2025 15:03:31 +0800 To: Baolin Wang , "linux-mm@kvack.org" , Linux Kernel Mailing List From: Liu Shixin Subject: Softlockup when test shmem swapout-swapin and compaction CC: Barry Song , David Hildenbrand , Hugh Dickins , Kefeng Wang , Lance Yang , Matthew Wilcox , Ryan Roberts , Andrew Morton Message-ID: <28546fb4-5210-bf75-16d6-43e1f8646080@huawei.com> Date: Wed, 26 Feb 2025 15:03:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemg200013.china.huawei.com (7.202.181.64) Hi all, I found a softlockup when testing shmem large folio swapout-swapin and compaction: watchdog: BUG: soft lockup - CPU#30 stuck for 179s! [folio_swap:4714] Modules linked in: zram xt_MASQUERADE nf_conntrack_netlink nfnetlink iptable_nat xt_addrtype iptable_filter ip_tantel_rapl_msr intel_rapl_common intel_uncore_frequency_common skx_edac_common nfit libnvdimm kvm_intel kvm rapl cixt4 mbcache jbd2 sr_mod cdrom ata_generic ata_piix virtio_net net_failover ghash_clmulni_intel libata sha512_ssse3 CPU: 30 UID: 0 PID: 4714 Comm: folio_swap Kdump: loaded Tainted: G L 6.14.0-rc4-next-20250225+ #2 Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 RIP: 0010:xas_load+0x5d/0xc0 Code: 08 48 d3 ea 83 e2 3f 89 d0 48 83 c0 04 48 8b 44 c6 08 48 89 73 18 48 89 c1 83 e1 03 48 83 f9 02 75 08 48 3d RSP: 0000:ffffadf142f1ba60 EFLAGS: 00000293 RAX: ffffe524cc4f6700 RBX: ffffadf142f1ba90 RCX: 0000000000000000 RDX: 0000000000000011 RSI: ffff9a3e058acb68 RDI: ffffadf142f1ba90 RBP: fffffffffffffffe R08: ffffadf142f1bb50 R09: 0000000000000392 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000011 R13: ffffadf142f1bb48 R14: ffff9a3e04e9c588 R15: 0000000000000000 FS: 00007fd957666740(0000) GS:ffff9a41ac0e5000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fd922860000 CR3: 000000025c360001 CR4: 0000000000772ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: ? watchdog_timer_fn+0x1c9/0x250 ? __pfx_watchdog_timer_fn+0x10/0x10 ? __hrtimer_run_queues+0x10e/0x250 ? hrtimer_interrupt+0xfb/0x240 ? __sysvec_apic_timer_interrupt+0x4e/0xe0 ? sysvec_apic_timer_interrupt+0x68/0x90 ? asm_sysvec_apic_timer_interrupt+0x16/0x20 ? xas_load+0x5d/0xc0 xas_find+0x153/0x1a0 find_get_entries+0x73/0x280 shmem_undo_range+0x1fc/0x640 shmem_evict_inode+0x109/0x270 evict+0x107/0x240 ? fsnotify_destroy_marks+0x25/0x180 ? _atomic_dec_and_lock+0x35/0x50 __dentry_kill+0x71/0x190 dput+0xd1/0x190 __fput+0x128/0x2a0 task_work_run+0x57/0x90 syscall_exit_to_user_mode+0x1cb/0x1e0 do_syscall_64+0x67/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7fd95776eb8b If CONFIG_DEBUG_VM is enabled, we will meet VM_BUG_ON_FOLIO(!folio_test_locked(folio)) in shmem_add_to_page_cache() too. It seems that the problem is related to memory migration or compaction which is necessary for reproduction, although without a clear why. To reproduce the problem, we need firstly a zram device as swap backend, and then run the reproduction program. The reproduction program consists of three parts: 1. A process constantly changes the status of shmem large folio by these interfaces: /sys/kernel/mm/transparent_hugepage/hugepages-/shmem_enabled 2. A process constantly echo 1 > /proc/sys/vm/compact_memory 3. A process constantly alloc/free/swapout/swapin shmem large folios. I'm not sure whether the first process is necessary but the second and third are. In addition, I tried hacking to modify compaction_alloc to return NULL, and the problem disappeared, so I guess the problem is in migration. The problem is different with https://lore.kernel.org/all/1738717785.im3r5g2vxc.none@localhost/ since I have confirmed this porblem still existed after merge the fixed patch. Thanks, Liu Shixin.