From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753959AbdBIPqZ (ORCPT ); Thu, 9 Feb 2017 10:46:25 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:59890 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753559AbdBIPqY (ORCPT ); Thu, 9 Feb 2017 10:46:24 -0500 Date: Thu, 9 Feb 2017 16:46:17 +0100 From: Peter Zijlstra To: Waiman Long Cc: Ingo Molnar , Thomas Gleixner , Linus Torvalds , Andrew Morton , "Paul E. McKenney" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] locking/spinlock_debug: Remove spinlock lockup detection code Message-ID: <20170209154617.GE6515@twins.programming.kicks-ass.net> References: <1486583208-11038-1-git-send-email-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1486583208-11038-1-git-send-email-longman@redhat.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 08, 2017 at 02:46:48PM -0500, Waiman Long wrote: > The current spinlock lockup detection code can sometimes produce false > positives because of the unfairness of the locking algorithm itself. Also, __delay(1) can be really terrible, which then causes the timeout to be highly variable and prone to triggering. > So the lockup detection code is now removed. Instead, we are relying > on the NMI watchdog to detect potential lockup. We won't have lockup > detection if the watchdog isn't running. > > The commented-out read-write lock lockup detection code are also > removed. Yes, this retains all the extra validation fields, which I've meanwhile heard are sometimes useful but does away with all the fragile bits. Thanks!