From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756043Ab3AVUy3 (ORCPT ); Tue, 22 Jan 2013 15:54:29 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:17364 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752392Ab3AVUy0 (ORCPT ); Tue, 22 Jan 2013 15:54:26 -0500 X-Authority-Analysis: v=2.0 cv=W/m6pGqk c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=8XPjA_W9iWwA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=cA-augn98TgA:10 a=KwsRBNIfCVfK20CjW1kA:9 a=PUjeQqilurYA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-ID: <1358888061.21576.57.camel@gandalf.local.home> Subject: Re: [PATCH v5 01/45] percpu_rwlock: Introduce the global reader-writer lock backend From: Steven Rostedt To: "Srivatsa S. Bhat" Cc: linux-doc@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, 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, sbw@mit.edu, tj@kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Date: Tue, 22 Jan 2013 15:54:21 -0500 In-Reply-To: <50FEEF5D.6080302@linux.vnet.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> <20130122073315.13822.27093.stgit@srivatsabhat.in.ibm.com> <1358883152.21576.55.camel@gandalf.local.home> <50FEEF5D.6080302@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 Wed, 2013-01-23 at 01:28 +0530, Srivatsa S. Bhat wrote: > > I thought global locks are now fair. That is, a reader will block if a > > writer is waiting. Hence, the above should deadlock on the current > > rwlock_t types. > > > > Oh is it? Last I checked, lockdep didn't complain about this ABBA scenario! It doesn't and Peter Zijlstra said we need to fix that ;-) It only recently became an issue with the new "fair" locking of rwlocks. -- Steve