From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761639Ab3EAP5q (ORCPT ); Wed, 1 May 2013 11:57:46 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:39852 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754740Ab3EAP5k (ORCPT ); Wed, 1 May 2013 11:57:40 -0400 Date: Wed, 1 May 2013 08:57:38 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Shawn Bohrer cc: xfs@oss.sgi.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: deadlock on vmap_area_lock In-Reply-To: <20130501144341.GA2404@BohrerMBP.rgmadvisors.com> Message-ID: References: <20130501144341.GA2404@BohrerMBP.rgmadvisors.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 1 May 2013, Shawn Bohrer wrote: > I've got two compute clusters with around 350 machines each which are > running kernels based off of 3.1.9 (Yes I realize this is ancient by > todays standards). All of the machines run a 'find' command once an > hour on one of the mounted XFS filesystems. Occasionally these find > commands get stuck requiring a reboot of the system. I took a peek > today and see this with perf: > > 72.22% find [kernel.kallsyms] [k] _raw_spin_lock > | > --- _raw_spin_lock > | > |--98.84%-- vm_map_ram > | _xfs_buf_map_pages > | xfs_buf_get > | xfs_buf_read > | xfs_trans_read_buf > | xfs_da_do_buf > | xfs_da_read_buf > | xfs_dir2_block_getdents > | xfs_readdir > | xfs_file_readdir > | vfs_readdir > | sys_getdents > | system_call_fastpath > | __getdents64 > | > |--1.12%-- _xfs_buf_map_pages > | xfs_buf_get > | xfs_buf_read > | xfs_trans_read_buf > | xfs_da_do_buf > | xfs_da_read_buf > | xfs_dir2_block_getdents > | xfs_readdir > | xfs_file_readdir > | vfs_readdir > | sys_getdents > | system_call_fastpath > | __getdents64 > --0.04%-- [...] > > Looking at the code my best guess is that we are spinning on > vmap_area_lock, but I could be wrong. This is the only process > spinning on the machine so I'm assuming either another process has > blocked while holding the lock, or perhaps this find process has tried > to acquire the vmap_area_lock twice? > Significant spinlock contention doesn't necessarily mean that there's a deadlock, but it also doesn't mean the opposite. Depending on your definition of "occassionally", would it be possible to run with CONFIG_PROVE_LOCKING and CONFIG_LOCKDEP to see if it uncovers any real deadlock potential?