From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756277Ab3BRQbd (ORCPT ); Mon, 18 Feb 2013 11:31:33 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:25782 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753954Ab3BRQbb (ORCPT ); Mon, 18 Feb 2013 11:31:31 -0500 X-Authority-Analysis: v=2.0 cv=UN5f7Vjy c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=o2Q8bu201zMA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=90TB_Sdg_p4A:10 a=CRI1Dda8Ao7ugpeRgCQA:9 a=PUjeQqilurYA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-ID: <1361205087.23152.159.camel@gandalf.local.home> Subject: Re: [PATCH v6 04/46] percpu_rwlock: Implement the core design of Per-CPU Reader-Writer Locks From: Steven Rostedt To: "Srivatsa S. Bhat" Cc: Michel Lespinasse , tglx@linutronix.de, peterz@infradead.org, tj@kernel.org, oleg@redhat.com, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org, wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com, rjw@sisk.pl, sbw@mit.edu, fweisbec@gmail.com, linux@arm.linux.org.uk, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, vincent.guittot@linaro.org Date: Mon, 18 Feb 2013 11:31:27 -0500 In-Reply-To: <5122551E.1080703@linux.vnet.ibm.com> References: <20130218123714.26245.61816.stgit@srivatsabhat.in.ibm.com> <20130218123856.26245.46705.stgit@srivatsabhat.in.ibm.com> <5122551E.1080703@linux.vnet.ibm.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.4-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2013-02-18 at 21:51 +0530, Srivatsa S. Bhat wrote: > Hi Michel, > Yes.. I don't think we can avoid that. Moreover, since we _want_ unfair > reader/writer semantics to allow flexible locking rules and guarantee > deadlock-safety, having a recursive reader side is not even an issue, IMHO. Recursive unfair reader lock may guarantee deadlock-safety, but remember, it adds a higher probability of live-locking the write_lock. Which is another argument to keep this separate to cpu hotplug only. -- Steve From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hrndva-omtalb.mail.rr.com (hrndva-omtalb.mail.rr.com [71.74.56.122]) by ozlabs.org (Postfix) with ESMTP id 7ED4E2C0293 for ; Tue, 19 Feb 2013 03:31:31 +1100 (EST) Message-ID: <1361205087.23152.159.camel@gandalf.local.home> Subject: Re: [PATCH v6 04/46] percpu_rwlock: Implement the core design of Per-CPU Reader-Writer Locks From: Steven Rostedt To: "Srivatsa S. Bhat" Date: Mon, 18 Feb 2013 11:31:27 -0500 In-Reply-To: <5122551E.1080703@linux.vnet.ibm.com> References: <20130218123714.26245.61816.stgit@srivatsabhat.in.ibm.com> <20130218123856.26245.46705.stgit@srivatsabhat.in.ibm.com> <5122551E.1080703@linux.vnet.ibm.com> Content-Type: text/plain; charset="ISO-8859-15" Mime-Version: 1.0 Cc: linux-doc@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, Michel Lespinasse , mingo@kernel.org, linux-arch@vger.kernel.org, linux@arm.linux.org.uk, xiaoguangrong@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, paulmck@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, rjw@sisk.pl, namhyung@kernel.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, oleg@redhat.com, vincent.guittot@linaro.org, sbw@mit.edu, tj@kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2013-02-18 at 21:51 +0530, Srivatsa S. Bhat wrote: > Hi Michel, > Yes.. I don't think we can avoid that. Moreover, since we _want_ unfair > reader/writer semantics to allow flexible locking rules and guarantee > deadlock-safety, having a recursive reader side is not even an issue, IMHO. Recursive unfair reader lock may guarantee deadlock-safety, but remember, it adds a higher probability of live-locking the write_lock. Which is another argument to keep this separate to cpu hotplug only. -- Steve From mboxrd@z Thu Jan 1 00:00:00 1970 From: rostedt@goodmis.org (Steven Rostedt) Date: Mon, 18 Feb 2013 11:31:27 -0500 Subject: [PATCH v6 04/46] percpu_rwlock: Implement the core design of Per-CPU Reader-Writer Locks In-Reply-To: <5122551E.1080703@linux.vnet.ibm.com> References: <20130218123714.26245.61816.stgit@srivatsabhat.in.ibm.com> <20130218123856.26245.46705.stgit@srivatsabhat.in.ibm.com> <5122551E.1080703@linux.vnet.ibm.com> Message-ID: <1361205087.23152.159.camel@gandalf.local.home> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, 2013-02-18 at 21:51 +0530, Srivatsa S. Bhat wrote: > Hi Michel, > Yes.. I don't think we can avoid that. Moreover, since we _want_ unfair > reader/writer semantics to allow flexible locking rules and guarantee > deadlock-safety, having a recursive reader side is not even an issue, IMHO. Recursive unfair reader lock may guarantee deadlock-safety, but remember, it adds a higher probability of live-locking the write_lock. Which is another argument to keep this separate to cpu hotplug only. -- Steve