From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964992AbWFTIEQ (ORCPT ); Tue, 20 Jun 2006 04:04:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965006AbWFTIEQ (ORCPT ); Tue, 20 Jun 2006 04:04:16 -0400 Received: from smtp.osdl.org ([65.172.181.4]:61325 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S964992AbWFTIEO (ORCPT ); Tue, 20 Jun 2006 04:04:14 -0400 Date: Tue, 20 Jun 2006 01:03:55 -0700 From: Andrew Morton To: Nick Piggin Cc: olson@unixfolk.com, mingo@elte.hu, ccb@acm.org, linux-kernel@vger.kernel.org Subject: Re: [patch] increase spinlock-debug looping timeouts (write_lock and NMI) Message-Id: <20060620010355.a4d1348a.akpm@osdl.org> In-Reply-To: <4497A5BC.4070005@yahoo.com.au> References: <20060619233947.94f7e644.akpm@osdl.org> <4497A5BC.4070005@yahoo.com.au> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.17; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 20 Jun 2006 17:37:32 +1000 Nick Piggin wrote: > >>Kernel panic - not syncing: nmi watchdog > > Any ideas what it might be waiting on? Readers, I guess. When there's a spinning writer, nothing prevents _new_ readers from getting into the read-locked region. If we have enough readers and the read-locked region is long enough, there's always at least one reader in the read-locked region and the writer is permanently starved. > Otherwise, a straight rwlock->spinlock conversion will have a few more > scalability issues, but I'd guess it wouldn't be a problem at all for > most workloads on most systems. It beats crashing.