Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754628Ab3IIQA3 (ORCPT ); Mon, 9 Sep 2013 12:00:29 -0400 Received: from mail-bk0-f50.google.com ([209.85.214.50]:39478 "EHLO mail-bk0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753760Ab3IIQA2 (ORCPT ); Mon, 9 Sep 2013 12:00:28 -0400 Date: Mon, 9 Sep 2013 18:00:24 +0200 From: Ingo Molnar To: Christoph Lameter Cc: Peter Zijlstra , "Paul E. McKenney" , Frederic Weisbecker , Eric Dumazet , linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, sbw@mit.edu Subject: Re: [PATCH] rcu: Is it safe to enter an RCU read-side critical section? Message-ID: <20130909160024.GA25555@gmail.com> References: <20130906151851.GQ3966@linux.vnet.ibm.com> <1378488088.31445.39.camel@edumazet-glaptop> <20130906174117.GU3966@linux.vnet.ibm.com> <20130906185927.GE2706@somewhere> <20130909105347.GK31370@twins.programming.kicks-ass.net> <20130909132343.GN3966@linux.vnet.ibm.com> <20130909133604.GC31370@twins.programming.kicks-ass.net> <000001410333127c-486c74ec-3209-4c5e-a92f-0c11e00fa141-000000@email.amazonses.com> <20130909150854.GD26785@twins.programming.kicks-ass.net> <0000014103534c88-48ee11a3-a581-4e52-b2df-3a1168047d96-000000@email.amazonses.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000014103534c88-48ee11a3-a581-4e52-b2df-3a1168047d96-000000@email.amazonses.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1842 Lines: 49 * Christoph Lameter wrote: > On Mon, 9 Sep 2013, Peter Zijlstra wrote: > > > > Slander. Certainly validation is good. Its just that PREEMPT kernels > > > are not in use > > > > Complete bullshit, its part of the mainline kernel, lots of people run > > them -- including me, and any patch is supposed to keep it working. > > Nonsense. There is no main line distro that supports full preempt. Its > an academic exercise. You are dead wrong on multiple levels. Firstly, here's a "popularity list" of preempt kernel config options, distilled from kernel configs sent to lkml, from a time span of a couple of months: 73 CONFIG_PREEMPT_NONE=y 81 CONFIG_PREEMPT_VOLUNTARY=y 135 CONFIG_PREEMPT=y CONFIG_PREEMPT=y is in fact more popular than the other two modes of preemption, amongst kernel testers who post configs to lkml. Secondly, even if, hypotethically, in an alternate universe, CONFIG_PREEMPT=y was used only rarely, the preempt debug checks are still very important for automated testing: they often catch bugs that are relevant on !PREEMPT as well. (such as accidental unlocked access) The last thing we want to do is to reduce the 'reach' of debug checks. Distros typically go for the lowest overhead preemption option with server loads in mind - still even they enjoy the bug fixes generated by the preempt checks. So my NAK stands: you are still in denial, you should stop the silly arguing and you should stop wasting maintainer time. You need to address PeterZ's review feedback and fix the bugs in your patches, ASAP. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/