From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id E90D16B01AF for ; Thu, 25 Mar 2010 23:18:22 -0400 (EDT) Date: Fri, 26 Mar 2010 03:18:14 +0000 From: Jamie Lokier Subject: Re: [rfc][patch] mm: lockdep page lock Message-ID: <20100326031814.GQ19308@shareable.org> References: <20100315155859.GE2869@laptop> <20100315180759.GA7744@quack.suse.cz> <20100316022153.GJ2869@laptop> <1269437291.5109.238.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1269437291.5109.238.camel@twins> Sender: owner-linux-mm@kvack.org To: Peter Zijlstra Cc: Nick Piggin , Jan Kara , Andrew Morton , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: Peter Zijlstra wrote: > On Tue, 2010-03-16 at 13:21 +1100, Nick Piggin wrote: > > > > > > Agreed (btw. Peter is there any way to turn lock debugging back on? > > it's annoying when cpufreq hotplug code or something early breaks and > > you have to reboot in order to do any testing). > > Not really, the only way to do that is to get the full system back into > a known (zero) lock state and then fully reset the lockdep state. How about: Set a variable nr_pending = number of CPUs, run a task on each CPU which disables interrupts, atomically decrements nr_pending and then spins waiting for it to become negative (raw, not counted in lockdep), and whichever one takes it to zero, that task knows there are no locks held, and can reset the lockdep state. Then sets it to -1 to wake everyone. -- Jamie -- 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/ . Don't email: email@kvack.org