From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751171AbeEATso (ORCPT ); Tue, 1 May 2018 15:48:44 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:33094 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750766AbeEATsn (ORCPT ); Tue, 1 May 2018 15:48:43 -0400 Date: Tue, 1 May 2018 21:48:38 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: Nicholas Piggin , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] tracing/irqtrace: only call trace_hardirqs_on/off when state changes Message-ID: <20180501194838.GK12217@hirez.programming.kicks-ass.net> References: <20171116161506.19691-1-npiggin@gmail.com> <20180501144620.1e832a09@gandalf.local.home> <20180501191951.GJ12217@hirez.programming.kicks-ass.net> <20180501153840.7281022a@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180501153840.7281022a@gandalf.local.home> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 01, 2018 at 03:38:40PM -0400, Steven Rostedt wrote: > On Tue, 1 May 2018 21:19:51 +0200 > Peter Zijlstra wrote: > > Now, lockdep only minimally tracks these otherwise redundant operations; > > see redundant_hardirqs_{on,off} counters, and loosing that doesn't seen > > like a big issue. > > > > But I'm confused how this helps track superfluous things, it looks like > > it explicitly tracks _less_ superfluous transitions. > > I think it is about triggering on OFF->OFF a warning, as that would > only happen if we have: > > local_irq_save(flags); > [..] > local_irq_disable(); > Ahh, ok. Yes, that is easier to do with these changes. The alternative is to add more information to the tracehooks such that we can do the same internally, but whatever. Yeah, I'm fine with the proposed change, but maybe improve the Changelog a little for slow people like me :-)