Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752082Ab2FMDfP (ORCPT ); Tue, 12 Jun 2012 23:35:15 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:34675 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751069Ab2FMDfN (ORCPT ); Tue, 12 Jun 2012 23:35:13 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1+g9kcwWgygWhvD6e4rrcApLYdkrogWeVYqQaklCU lYU8y7HpaZrfRA Message-ID: <1339558508.7472.26.camel@marge.simpson.net> Subject: Re: rcu: endless stalls From: Mike Galbraith To: paulmck@linux.vnet.ibm.com Cc: LKML , Miklos Szeredi , Hugh Dickins Date: Wed, 13 Jun 2012 05:35:08 +0200 In-Reply-To: <1339438242.7358.62.camel@marge.simpson.net> References: <1339409176.7350.26.camel@marge.simpson.net> <20120611133953.GI2425@linux.vnet.ibm.com> <1339424543.7350.101.camel@marge.simpson.net> <1339435214.7358.43.camel@marge.simpson.net> <20120611180112.GD2521@linux.vnet.ibm.com> <1339438242.7358.62.camel@marge.simpson.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1360 Lines: 36 On Mon, 2012-06-11 at 20:10 +0200, Mike Galbraith wrote: > On Mon, 2012-06-11 at 11:01 -0700, Paul E. McKenney wrote: > > > 2aa15890 - mm: prevent concurrent unmap_mapping_range() on the same inode > > > > I confess, you lost me on this one. You believe that this commit is > > the cause of the RCU CPU stall warnings? > > 4096 tasks on 4096 CPUs exit (well, try to) simultaneously. > > Call Trace: > __mutex_lock_slowpath+0x94/0x150 > mutex_lock+0x1a/0x40 > unlink_file_vma+0x3f/0xf0 > free_pgtables+0x40/0x100 > exit_mmap+0xb0/0x120 > mmput+0x49/0x120 > exit_mm+0x122/0x160 > do_exit+0x179/0x8d0 > do_group_exit+0x3d/0xb0 > sys_exit_group+0x12/0x20 > > Monster box dies screaming. That commit landed in stable, box with way too many cores (NR_CPUS=0!!) chokes instantly with loads of spinners. Ok, so zillion CPUs grabbing a mutex in lockstep is a bad idea (_having_ zillion?), but is there pilot error involved in a logjam like this? -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/