From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH RFC 6/9] RCU priority boosting for preemptible RCU Date: Sat, 29 Sep 2007 20:11:31 -0700 Message-ID: <20070930031131.GF9119@linux.vnet.ibm.com> References: <20070910183004.GA3299@linux.vnet.ibm.com> <20070910183901.GF3819@linux.vnet.ibm.com> <20070928225649.GA9899@in.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Gautham R Shenoy , LKML , linux-rt-users , Ingo Molnar , akpm@linux-foundation.org, dipankar@in.ibm.com, josht@linux.vnet.ibm.com, tytso@us.ibm.com, dvhltc@us.ibm.com, Thomas Gleixner , a.p.zijlstra@chello.nl, bunk@kernel.org, oleg@tv-sign.ru, srostedt@redhat.com To: Steven Rostedt Return-path: Received: from e5.ny.us.ibm.com ([32.97.182.145]:37603 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753144AbXI3DLj (ORCPT ); Sat, 29 Sep 2007 23:11:39 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Fri, Sep 28, 2007 at 07:05:14PM -0400, Steven Rostedt wrote: > > > -- > On Fri, 28 Sep 2007, Gautham R Shenoy wrote: > > > > > > > +#ifdef CONFIG_PREEMPT_RCU_BOOST > > > +/* > > > + * Task state with respect to being RCU-boosted. This state is changed > > > + * by the task itself in response to the following three events: > > ^^^ > > > + * 1. Preemption (or block on lock) while in RCU read-side critical section. > > > > I am wondering, can a task block on a lock while in RCU read-side > > critical section? > > I think this may be specific to the -rt patch. In the -rt patch, > spin_locks turn into mutexes, and therefor can block a read-side critical > section. Yep! I do need to fix the comment. > > > + * 2. Outermost rcu_read_unlock() for blocked RCU read-side critical section. > > > + * > > > > Event #3. is missing? > > I guess Paul needs to answer that one ;-) An older version had three, the new one has two, and I forgot to s/three/two/. Thanx, Paul