From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f70.google.com (mail-vk0-f70.google.com [209.85.213.70]) by kanga.kvack.org (Postfix) with ESMTP id B72EB6B026E for ; Mon, 30 Jan 2017 10:48:30 -0500 (EST) Received: by mail-vk0-f70.google.com with SMTP id k127so189742891vke.7 for ; Mon, 30 Jan 2017 07:48:30 -0800 (PST) Received: from mail-ua0-x22d.google.com (mail-ua0-x22d.google.com. [2607:f8b0:400c:c08::22d]) by mx.google.com with ESMTPS id j34si3888669uad.92.2017.01.30.07.48.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 30 Jan 2017 07:48:29 -0800 (PST) Received: by mail-ua0-x22d.google.com with SMTP id 96so252519636uaq.3 for ; Mon, 30 Jan 2017 07:48:29 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: From: Dmitry Vyukov Date: Mon, 30 Jan 2017 16:48:08 +0100 Message-ID: Subject: Re: mm: deadlock between get_online_cpus/pcpu_alloc Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Tejun Heo , Christoph Lameter , "linux-mm@kvack.org" , LKML , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , syzkaller , Mel Gorman , Michal Hocko , Andrew Morton On Sun, Jan 29, 2017 at 6:22 PM, Vlastimil Babka wrote: > On 29.1.2017 13:44, Dmitry Vyukov wrote: >> Hello, >> >> I've got the following deadlock report while running syzkaller fuzzer >> on f37208bc3c9c2f811460ef264909dfbc7f605a60: >> >> [ INFO: possible circular locking dependency detected ] >> 4.10.0-rc5-next-20170125 #1 Not tainted >> ------------------------------------------------------- >> syz-executor3/14255 is trying to acquire lock: >> (cpu_hotplug.dep_map){++++++}, at: [] >> get_online_cpus+0x37/0x90 kernel/cpu.c:239 >> >> but task is already holding lock: >> (pcpu_alloc_mutex){+.+.+.}, at: [] >> pcpu_alloc+0xbfe/0x1290 mm/percpu.c:897 >> >> which lock already depends on the new lock. > > I suspect the dependency comes from recent changes in drain_all_pages(). They > were later redone (for other reasons, but nice to have another validation) in > the mmots patch [1], which AFAICS is not yet in mmotm and thus linux-next. Could > you try if it helps? It happened only once on linux-next, so I can't verify the fix. But I will watch out for other occurrences. -- 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