From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx195.postini.com [74.125.245.195]) by kanga.kvack.org (Postfix) with SMTP id AB7896B0044 for ; Fri, 30 Mar 2012 18:35:21 -0400 (EDT) Date: Fri, 30 Mar 2012 15:35:19 -0700 From: Andrew Morton Subject: Re: mm: migrate_pages hang Message-Id: <20120330153519.1e80735b.akpm@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin Cc: Andrea Arcangeli , Hugh Dickins , Thomas Gleixner , linux-mm@kvack.org, "linux-kernel@vger.kernel.org List" , Dave Jones On Sat, 31 Mar 2012 00:23:30 +0200 Sasha Levin wrote: > Hi all, > > I saw the following inside a KVM guest, this is the first time I > observed this hang and it seems to have started with today's > (20120330) -next. > > [ 3122.093136] INFO: task trinity:17328 blocked for more than 120 seconds. > [ 3122.093807] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" > disables this message. > [ 3122.095237] trinity D ffff8800703284d8 5648 17328 3101 0x00000004 > [ 3122.096543] ffff8800064cfb08 0000000000000082 ffff8800064cfab8 > ffffffff8107d346 > [ 3122.098087] ffff8800064cffd8 00000000001d4580 ffff8800064ce010 > 00000000001d4580 > [ 3122.099447] 00000000001d4580 00000000001d4580 ffff8800064cffd8 > 00000000001d4580 > [ 3122.100607] Call Trace: > [ 3122.100983] [] ? kvm_clock_read+0x46/0x80 > [ 3122.101950] [] ? __lock_page+0x70/0x70 > [ 3122.102761] [] schedule+0x24/0x70 > [ 3122.103576] [] io_schedule+0x87/0xd0 > [ 3122.104371] [] sleep_on_page+0x9/0x10 > [ 3122.105179] [] __wait_on_bit_lock+0x52/0xb0 > [ 3122.106042] [] __lock_page+0x62/0x70 > [ 3122.106811] [] ? autoremove_wake_function+0x40/0x40 > [ 3122.107450] [] lock_page+0x39/0x40 > [ 3122.107976] [] __unmap_and_move+0x274/0x280 > [ 3122.108848] [] ? list_del+0x11/0x40 > [ 3122.109385] [] unmap_and_move+0x8d/0x130 > [ 3122.109957] [] migrate_pages+0xab/0x150 > [ 3122.110788] [] ? isolate_freepages+0x390/0x390 > [ 3122.111399] [] compact_zone+0x1e1/0x2a0 > [ 3122.111935] [] ? _raw_spin_unlock_irqrestore+0x75/0xa0 > [ 3122.112579] [] __compact_pgdat+0x1b3/0x200 > [ 3122.113199] [] compact_node+0x37/0x40 > [ 3122.113631] [] ? lru_add_drain_all+0x10/0x20 > [ 3122.114266] [] sysfs_compact_node+0x48/0x60 > [ 3122.114768] [] ? sysfs_write_file+0x82/0xf0 > [ 3122.115368] [] dev_attr_store+0x1b/0x20 > [ 3122.115877] [] sysfs_write_file+0x9e/0xf0 > [ 3122.116423] [] vfs_write+0xc8/0x190 > [ 3122.116934] [] sys_write+0x4f/0x90 > [ 3122.117697] [] system_call_fastpath+0x16/0x1b > [ 3122.118354] 2 locks held by trinity/17328: > [ 3122.118694] #0: (&buffer->mutex){+.+.+.}, at: > [] sysfs_write_file+0x44/0xf0 > [ 3122.119498] #1: (s_active#57){.+.+.+}, at: [] > sysfs_write_file+0x82/0xf0 You reported what I suppose is the same bug a week ago ("mm: hung task (handle_pte_fault)"): the kernel is waiting for a page to come unlocked, thinking that there is I/O outstanding against it. And my ugh still applies: "There are quite a lot of things which could cause this, alas. VM, readahead, scheduler, core wait/wakeup code, IO system, interrupt system (if it happens outside KVM, I guess). So.... ugh. Hopefully someone will hit this in a situation where it can be narrowed down or bisected." -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org