From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f70.google.com (mail-lf0-f70.google.com [209.85.215.70]) by kanga.kvack.org (Postfix) with ESMTP id 56564280266 for ; Mon, 26 Sep 2016 03:47:00 -0400 (EDT) Received: by mail-lf0-f70.google.com with SMTP id b71so106939498lfg.2 for ; Mon, 26 Sep 2016 00:47:00 -0700 (PDT) Received: from mail-lf0-f43.google.com (mail-lf0-f43.google.com. [209.85.215.43]) by mx.google.com with ESMTPS id f18si8127888lfg.279.2016.09.26.00.46.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Sep 2016 00:46:58 -0700 (PDT) Received: by mail-lf0-f43.google.com with SMTP id l131so132956584lfl.2 for ; Mon, 26 Sep 2016 00:46:58 -0700 (PDT) From: Nikolay Borisov Subject: Soft lockup in __slab_free (SLUB) Message-ID: <57E8D270.8040802@kyup.com> Date: Mon, 26 Sep 2016 10:46:56 +0300 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Linux MM , brouer@redhat.com, js1304@gmail.com Hello, On 4.4.14 stable kernel I observed the following soft-lockup, however I also checked that the code is the same in 4.8-rc so the problem is present there as well: [434575.862377] NMI watchdog: BUG: soft lockup - CPU#13 stuck for 23s! [swapper/13:0] [434575.866352] CPU: 13 PID: 0 Comm: swapper/13 Tainted: P O 4.4.14-clouder5 #2 [434575.866643] Hardware name: Supermicro X9DRD-iF/LF/X9DRD-iF, BIOS 3.0b 12/05/2013 [434575.866932] task: ffff8803714aadc0 ti: ffff8803714c4000 task.ti: ffff8803714c4000 [434575.867221] RIP: 0010:[] [] _raw_spin_unlock_irqrestore+0x1c/0x30 [434575.867566] RSP: 0018:ffff880373ce3dc0 EFLAGS: 00000203 [434575.867736] RAX: ffff88066e0c9a40 RBX: 0000000000000203 RCX: 0000000000000000 [434575.868023] RDX: 0000000000000008 RSI: 0000000000000203 RDI: ffff88066e0c9a40 [434575.868311] RBP: ffff880373ce3dc8 R08: ffff8803e5c1d118 R09: ffff8803e5c1d538 [434575.868609] R10: 0000000000000000 R11: ffffea000f970600 R12: ffff88066e0c9a40 [434575.868895] R13: ffffea000f970600 R14: 000000000046cf3b R15: ffff88036f8e3200 [434575.869183] FS: 0000000000000000(0000) GS:ffff880373ce0000(0000) knlGS:0000000000000000 [434575.869472] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [434575.869643] CR2: ffffffffff600400 CR3: 0000000367201000 CR4: 00000000001406e0 [434575.869931] Stack: [434575.870095] ffff88066e0c9a40 ffff880373ce3e78 ffffffff8117ea8a ffff880373ce3e08 [434575.870567] 000000000046bd03 0000000100170017 ffff8803e5c1d118 ffff8803e5c1d118 [434575.871037] 00ff000100000000 0000000000000203 0000000000000000 ffffffff8123d9ac [434575.874253] Call Trace: [434575.874418] [434575.874473] [] __slab_free+0xca/0x290 [434575.874806] [] ? ext4_i_callback+0x1c/0x20 [434575.874978] [] kmem_cache_free+0x1ea/0x200 [434575.875149] [] ext4_i_callback+0x1c/0x20 [434575.875325] [] rcu_process_callbacks+0x21b/0x620 [434575.875506] [] __do_softirq+0x147/0x310 [434575.875680] [] irq_exit+0x5f/0x70 [434575.875851] [] smp_apic_timer_interrupt+0x42/0x50 [434575.876025] [] apic_timer_interrupt+0x89/0x90 [434575.876197] [434575.876250] [] ? cpuidle_enter_state+0x141/0x2c0 [434575.876583] [] ? cpuidle_enter_state+0x136/0x2c0 [434575.876755] [] cpuidle_enter+0x17/0x20 [434575.876929] [] cpu_startup_entry+0x2fc/0x360 [434575.877105] [] start_secondary+0xf3/0x100 The ip in __slab_free points to this piece of code (in mm/slub.c): if (unlikely(n)) { spin_unlock_irqrestore(&n->list_lock, flags); n = NULL; } I think it's a pure chance that the spin_unlock_restore is being shown in this trace, do you think that a cond_resched is needed in this unlikely if clause? Apparently there are cases where this loop can take a considerable amount of time. How about this patch: diff --git a/mm/slub.c b/mm/slub.c index 65d5f92d51d2..daa20f38770a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2654,6 +2654,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page, if (unlikely(n)) { spin_unlock_irqrestore(&n->list_lock, flags); n = NULL; + cond_resched(); } prior = page->freelist; counters = page->counters; Regards, Nikolay -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org