From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id DAECCB1E for ; Wed, 5 Jul 2017 15:09:54 +0000 (UTC) Received: from bedivere.hansenpartnership.com (bedivere.hansenpartnership.com [66.63.167.143]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 643D93DC for ; Wed, 5 Jul 2017 15:09:54 +0000 (UTC) Message-ID: <1499267389.3668.16.camel@HansenPartnership.com> From: James Bottomley To: Steven Rostedt Date: Wed, 05 Jul 2017 08:09:49 -0700 In-Reply-To: <20170705105651.5da9c969@gandalf.local.home> References: <576cea07-770a-4864-c3f5-0832ff211e94@leemhuis.info> <20170703123025.7479702e@gandalf.local.home> <20170705084528.67499f8c@gandalf.local.home> <4080ecc7-1aa8-2940-f230-1b79d656cdb4@redhat.com> <20170705092757.63dc2328@gandalf.local.home> <20170705140607.GA30187@kroah.com> <20170705143341.oees22k2snhtmkxo@sirena.org.uk> <20170705103658.226099c6@gandalf.local.home> <1499266228.3668.10.camel@HansenPartnership.com> <20170705105651.5da9c969@gandalf.local.home> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Carlos O'Donell , linux-api@vger.kernel.org, Shuah Khan , ksummit-discuss@lists.linuxfoundation.org, Thorsten Leemhuis Subject: Re: [Ksummit-discuss] [MAINTAINERS SUMMIT] & [TECH TOPIC] Improve regression tracking List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2017-07-05 at 10:56 -0400, Steven Rostedt wrote: > On Wed, 05 Jul 2017 07:50:28 -0700 > James Bottomley wrote: > > > > > On Wed, 2017-07-05 at 10:36 -0400, Steven Rostedt wrote: > > > > > > On Wed, 5 Jul 2017 15:33:41 +0100 > > > Mark Brown wrote: > > >    > > > > > > > > > > > > On Wed, Jul 05, 2017 at 04:06:07PM +0200, Greg KH wrote: > > > >    > > > > > > > > > > > > > > > I don't mean to poo-poo the idea, but please realize that > > > > > around 75% of the kernel is hardware/arch support, so that > > > > > means that 75% of the changes/fixes deal with hardware things > > > > > (yes, change is in direct correlation to size of the codebase > > > > > in the tree, strange but true).     > > > > > > > > Then add in all the fixes for concurrency/locking issues and so > > > > on that're hard to reliably reproduce as well...   > > > > > > All tests should be run with lockdep enabled ;-)  Which a > > > surprising few developers appear to do :-p   > > > > Lockdep checks the locking hierarchies and makes assumptions about > > them which it then validates ... it doesn't tell you if the data > > you think > > We should probably look at adding infrastructure that helps in that. > RCU already has a lot of there to help know if data is being > protected by RCU or not. > > Hmm, maybe we could add a __rcu like type that we can associate > protected data with, where a config can associate access to a > variable with a lock being held? That's about 10x more complex than the releases/acquires/must_hold annotation, which we have fairly dismal coverage on. If you remember the hotplug annotations, which were a shining example: there's a limit of complexity before any annotation system simply becomes a make work tyranny.  > > you're protecting was accessed outside the lock, which is the usual > > source of concurrency problems.  In other words lockdep is useful > > but it's not a panacea. > > Still not an excuse to not have lockdep enabled during tests. OK, what makes you think lockdep isn't enabled?  Since Kconfig is so complex, I usually use a distro config ... they have it enabled (or at least openSUSE does), so it's enabled for everything I do. James