From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx194.postini.com [74.125.245.194]) by kanga.kvack.org (Postfix) with SMTP id 43AF26B0044 for ; Mon, 26 Mar 2012 19:17:07 -0400 (EDT) Date: Mon, 26 Mar 2012 16:17:05 -0700 From: Andrew Morton Subject: Re: mm: hung task (handle_pte_fault) Message-Id: <20120326161705.b96636db.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: Hugh Dickins , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Pekka Enberg , Dave Jones , linux-mm@kvack.org, "linux-kernel@vger.kernel.org List" On Fri, 23 Mar 2012 12:45:03 +0200 Sasha Levin wrote: > Hi guys, > > During fuzzing using trinity inside a KVM tools guest with latest > linux-next, I seem to be getting it hung once in a while, with the > following spew: > > [ 1441.420617] INFO: task trinity:2706 blocked for more than 120 seconds. > [ 1441.421894] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" > disables this message. > [ 1441.424493] trinity D 0000000000000000 3472 2706 16846 0x00000004 > [ 1441.426749] ffff880029dbbb38 0000000000000086 ffff880029dbbae8 > ffff880029dbbfd8 > [ 1441.428582] 00000000001d45c0 ffff880029dba000 00000000001d45c0 > 00000000001d45c0 > [ 1441.430156] 00000000001d45c0 00000000001d45c0 ffff880029dbbfd8 > 00000000001d45c0 > [ 1441.432371] Call Trace: > [ 1441.433042] [] ? file_read_actor+0x1d0/0x1d0 > [ 1441.434251] [] schedule+0x24/0x70 > [ 1441.435314] [] io_schedule+0x87/0xd0 > [ 1441.436357] [] sleep_on_page+0x9/0x10 > [ 1441.437442] [] __wait_on_bit+0x57/0x80 > [ 1441.438584] [] ? __lock_page_or_retry+0x8f/0xd0 > [ 1441.439948] [] wait_on_page_bit+0x6e/0x80 > [ 1441.440859] [] ? autoremove_wake_function+0x40/0x40 > [ 1441.441700] [] ? up_read+0x1e/0x40 > [ 1441.442428] [] __lock_page_or_retry+0xc6/0xd0 > [ 1441.443270] [] filemap_fault+0x440/0x4e0 > [ 1441.444072] [] __do_fault+0x7f/0x5f0 > [ 1441.444829] [] ? > add_lock_to_list.clone.18.clone.27+0xd0/0xe0 > [ 1441.445886] [] handle_pte_fault+0xf7/0x1e0 > [ 1441.446740] [] handle_mm_fault+0x1ce/0x330 > [ 1441.447537] [] __get_user_pages+0x14c/0x640 > [ 1441.448399] [] ? put_lock_stats.clone.19+0xe/0x40 > [ 1441.449288] [] ? __lock_acquired+0x19d/0x270 > [ 1441.450164] [] __mlock_vma_pages_range+0x87/0xa0 > [ 1441.451127] [] do_mlock_pages+0x89/0x160 > [ 1441.451932] [] sys_mlockall+0x111/0x1a0 > [ 1441.452761] [] system_call_fastpath+0x1a/0x1f > [ 1441.453659] no locks held by trinity/2706. > [ 1441.454267] Kernel panic - not syncing: hung_task: blocked tasks > > According to the logs, it's not the direct result of anything specific > happening, so I can't give an exact scenario to reproduce it. It does > happen rather often. The task is waiting for IO to complete against a page, and it isn't happening. 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