From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 3 Jun 2016 13:35:37 +0200 From: Peter Zijlstra Subject: Re: [lockdep] chain_key collision check triggers Message-ID: <20160603113537.GJ3190@twins.programming.kicks-ass.net> References: <20160603071544.GA3472@osiris> <20160603084801.GG3190@twins.programming.kicks-ass.net> <20160603111250.GB3472@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160603111250.GB3472@osiris> Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Heiko Carstens Cc: Alfredo Alvarez Fernandez , Ingo Molnar , Shuah Khan , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org List-ID: On Fri, Jun 03, 2016 at 01:12:50PM +0200, Heiko Carstens wrote: > On Fri, Jun 03, 2016 at 10:48:01AM +0200, Peter Zijlstra wrote: > > On Fri, Jun 03, 2016 at 09:15:44AM +0200, Heiko Carstens wrote: > > > Hi all, > > > > > > the new lockdep chain_key collision detection code triggers quite reliably > > > on s390, so it looks like we need a different iterate_chain_key() > > > implementation? > > > > That too, I have one queued up; but if you can realiably trigger this > > that's 'good' news. Most reports so far have been one offs that people > > could not reproduce. > > > > Let me wake up a bit more, but in the meantime, the below is what I had > > queued. > > > > --- > > Subject: locking,lockdep: Use __jhash_mix for iterate_chain_key > > From: Peter Zijlstra > > Date: Mon May 30 18:31:33 CEST 2016 > > > > Use __jhash_mix() to mix the class_idx into the class_key. This > > function provides better mixing than the previously used, home grown > > mix function. > > Ok, thanks! I'll use that then. Unfortunately the new hash function > generates 28 instead of 2 instructions on s390. Yeah, but I doubt you can actually measure the performance difference, lockdep is a pig anyway.