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 087412C0079 for ; Wed, 23 Jan 2013 07:54:26 +1100 (EST) 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" 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" Mime-Version: 1.0 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 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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