Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759551Ab3D2XLU (ORCPT ); Mon, 29 Apr 2013 19:11:20 -0400 Received: from ja.ssi.bg ([178.16.129.10]:54746 "EHLO ja.ssi.bg" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1759231Ab3D2XLR (ORCPT ); Mon, 29 Apr 2013 19:11:17 -0400 Date: Tue, 30 Apr 2013 02:12:10 +0300 (EEST) From: Julian Anastasov To: "Paul E. McKenney" cc: Eric Dumazet , Peter Zijlstra , Simon Horman , Ingo Molnar , lvs-devel@vger.kernel.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, linux-kernel@vger.kernel.org, Pablo Neira Ayuso , Dipankar Sarma , dhaval.giani@gmail.com Subject: Re: [PATCH 2/2] ipvs: Use cond_resched_rcu_lock() helper when dumping connections In-Reply-To: <20130429213002.GP3780@linux.vnet.ibm.com> Message-ID: References: <1366940708-10180-1-git-send-email-horms@verge.net.au> <1366940708-10180-3-git-send-email-horms@verge.net.au> <20130426080313.GC8669@dyad.programming.kicks-ass.net> <20130426154547.GC3860@linux.vnet.ibm.com> <20130426171948.GA31467@dyad.programming.kicks-ass.net> <20130426174815.GI3860@linux.vnet.ibm.com> <1367000815.8964.243.camel@edumazet-glaptop> <20130427162049.GB3780@linux.vnet.ibm.com> <20130429213002.GP3780@linux.vnet.ibm.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1943 Lines: 67 Hello, On Mon, 29 Apr 2013, Paul E. McKenney wrote: > On Tue, Apr 30, 2013 at 12:08:18AM +0300, Julian Anastasov wrote: > > > > Hello, > > > > On Sat, 27 Apr 2013, Paul E. McKenney wrote: > > > > > I would instead suggest something like: > > > > > > #ifndef CONFIG_PREEMPT_RCU > > > > > > But yes, in the CONFIG_PREEMPT_RCU case, the cond_resched() is not > > > needed. > > > > Hm, is this correct? If I follow the ifdefs > > preempt_schedule is called when CONFIG_PREEMPT is > > defined _and_ CONFIG_PREEMPT_RCU is not defined. > > Your example for CONFIG_PREEMPT_RCU is the opposite to this? > > Yep, I really did intend to say "#ifndef CONFIG_PREEMPT_RCU". > > A couple of things to keep in mind: > > 1. Although rcu_read_unlock() does map to preempt_enable() for > CONFIG_TINY_RCU and CONFIG_TREE_RCU, the current Kconfig refuses > to allow either CONFIG_TINY_RCU or CONFIG_TREE_RCU to be selected > if CONFIG_PREEMPT=y. I see, CONFIG_PREEMPT_RCU depends on CONFIG_PREEMPT > 2. In the CONFIG_PREEMPT_RCU case, __rcu_read_unlock() will check > to see if the RCU core needs to be informed, so there is no > need to invoke cond_resched() in that case. OK > 3. If we drop your "|| defined(CONFIG_PREEMPT_RCU)", we get an > almost-synonym for my "#ifndef CONFIG_PREEMPT_RCU". The "almost" > applies to older kernels due to the possibility of having a > CONFIG_TINY_PREEMPT_RCU kernel -- but this possibility is going > away soon. > > Make sense? Yes, thanks for the explanation! Simon, so lets do it as suggested by Eric and Paul: rcu_read_unlock(); #ifndef CONFIG_PREEMPT_RCU cond_resched(); #endif rcu_read_lock(); Regards -- Julian Anastasov -- 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/