From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754195AbZBTSS4 (ORCPT ); Fri, 20 Feb 2009 13:18:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752488AbZBTSSr (ORCPT ); Fri, 20 Feb 2009 13:18:47 -0500 Received: from bc.sympatico.ca ([209.226.175.184]:40958 "EHLO tomts22-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751838AbZBTSSq (ORCPT ); Fri, 20 Feb 2009 13:18:46 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AkwFAGF/nklMQWt2/2dsb2JhbACBbtMUhA8G Date: Fri, 20 Feb 2009 13:18:35 -0500 From: Mathieu Desnoyers To: "Paul E. McKenney" Cc: ltt-dev@lists.casi.polymtl.ca, bert.wesarg@googlemail.com, bob@watson.ibm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH URCU formal] Add liveness checks to user-level RCU model. Message-ID: <20090220181835.GA4092@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 13:17:08 up 50 days, 18:15, 4 users, load average: 0.58, 0.39, 0.32 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote: > Break all potentially infinite loops in both urcu_reader() and > urcu_updater(), ensure that urcu_reader() will process any memory barriers > that urcu_updater() might issue, and formulate a "never" claim that checks > to make sure that if either urcu_reader() or urcu_updater() completes, > then the other will eventually also complete. Since urcu_reader() > now has a finite number of steps, it must eventually complete. > > Also replace the code at the end of urcu_reader() that previously absorbed > late memory-barrier requests from urcu_updater with code in urcu_writer() > that checks to see if urcu_reader() has completed. > > Signed-off-by: Paul E. McKenney Thanks Paul, I'll merge it. However, I am currently reworking our spin tree so we can execute the tests in batch (rather that all at once, which consumes more memory than necessary) and also I am doing a nice build script which lets us create our own LTL formulaes for verification. The never claims will be automatically generated and verified. I'll keep you posted. Mathieu > --- > formal-model/urcu.sh | 26 ++++++++++- > formal-model/urcu.spin | 113 ++++++++++++++++++++++------------------------- > 2 files changed, 77 insertions(+), 62 deletions(-) > > diff --git a/formal-model/urcu.sh b/formal-model/urcu.sh > index b76c764..5e525ec 100644 > --- a/formal-model/urcu.sh > +++ b/formal-model/urcu.sh > @@ -1,3 +1,25 @@ > +#!/bin/sh > +# > +# Compiles and runs the urcu.spin Promela model. > +# > +# This program is free software; you can redistribute it and/or modify > +# it under the terms of the GNU General Public License as published by > +# the Free Software Foundation; either version 2 of the License, or > +# (at your option) any later version. > +# > +# This program is distributed in the hope that it will be useful, > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +# GNU General Public License for more details. > +# > +# You should have received a copy of the GNU General Public License > +# along with this program; if not, write to the Free Software > +# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. > +# > +# Copyright (C) IBM Corporation, 2009 > +# > +# Authors: Paul E. McKenney > + > spin -a urcu.spin > -cc -DSAFETY -o pan pan.c > -./pan > +cc -o pan pan.c > +./pan -a > diff --git a/formal-model/urcu.spin b/formal-model/urcu.spin > index 3e18457..cf1f670 100644 > --- a/formal-model/urcu.spin > +++ b/formal-model/urcu.spin > @@ -40,21 +40,28 @@ bit updater_done = 0; > byte urcu_gp_ctr = 1; > byte urcu_active_readers = 0; > > +/* must be at least the number of smp_mb() statements in urcu_updater(). */ > +#define N_SMP_MB 9 > + > /* Model the RCU read-side critical section. */ > > proctype urcu_reader() > { > bit done = 0; > + byte i; > bit mbok; > byte tmp; > byte tmp_removed; > byte tmp_free; > > /* Absorb any early requests for memory barriers. */ > + i = 0; > do > - :: need_mb == 1 -> > + :: i < N_SMP_MB && need_mb == 1 -> > need_mb = 0; > - :: !updater_done -> skip; > + i++; > + :: i < N_SMP_MB -> > + i++; > :: 1 -> break; > od; > > @@ -91,12 +98,17 @@ proctype urcu_reader() > if > :: (tmp & RCU_GP_CTR_NEST_MASK) == 0 -> > tmp = urcu_gp_ctr; > + i = 0; > do > - :: (reader_progress[1] + > + :: i < N_SMP_MB && > + (reader_progress[1] + > reader_progress[2] + > - reader_progress[3] == 0) && need_mb == 1 -> > + reader_progress[3] == 0) && > + need_mb == 1 -> > need_mb = 0; > - :: !updater_done -> skip; > + i++; > + :: i < N_SMP_MB -> > + i++; > :: 1 -> break; > od; > urcu_active_readers = tmp; > @@ -151,10 +163,13 @@ proctype urcu_reader() > if > :: mbok == 1 -> > /* We get here if mb processing is safe. */ > + i = 0; > do > - :: need_mb == 1 -> > + :: i < N_SMP_MB && need_mb == 1 -> > need_mb = 0; > - :: !updater_done -> skip; > + i++; > + :: i < N_SMP_MB -> > + i++; > :: 1 -> break; > od; > :: else -> skip; > @@ -169,36 +184,30 @@ proctype urcu_reader() > :: else -> skip; > fi > od; > + > + /* Make sure any concurrent grace period was sufficiently long. */ > assert((tmp_free == 0) || (tmp_removed == 1)); > > /* Reader has completed. */ > reader_done = 1; > - > - /* Process any late-arriving memory-barrier requests. */ > - do > - :: need_mb == 1 -> > - need_mb = 0; > - :: !updater_done -> skip; > - :: 1 -> break; > - od; > } > > +#define smp_mb() \ > + need_mb = 1; \ > + do \ > + :: !reader_done && need_mb == 1 -> skip; \ > + :: reader_done -> break; \ > + :: need_mb == 0 -> break; \ > + od > + > /* Model the RCU update process. */ > > proctype urcu_updater() > { > /* prior synchronize_rcu(), second counter flip. */ > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > urcu_gp_ctr = urcu_gp_ctr + RCU_GP_CTR_BIT; > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > do > :: 1 -> > if > @@ -209,27 +218,15 @@ proctype urcu_updater() > :: else -> break; > fi; > od; > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > > /* Removal statement, e.g., list_del_rcu(). */ > removed = 1; > > /* current synchronize_rcu(), first counter flip. */ > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > urcu_gp_ctr = urcu_gp_ctr + RCU_GP_CTR_BIT; > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > do > :: 1 -> > if > @@ -240,24 +237,12 @@ proctype urcu_updater() > :: else -> break; > fi; > od; > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > > /* current synchronize_rcu(), second counter flip. */ > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > urcu_gp_ctr = urcu_gp_ctr + RCU_GP_CTR_BIT; > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > do > :: 1 -> > if > @@ -268,11 +253,7 @@ proctype urcu_updater() > :: else -> break; > fi; > od; > - need_mb = 1; > - do > - :: need_mb == 1 -> skip; > - :: need_mb == 0 -> break; > - od; > + smp_mb(); > > /* free-up step, e.g., kfree(). */ > free = 1; > @@ -299,3 +280,15 @@ init { > run urcu_updater(); > } > } > + > +/* Require that both reader and updater eventually get done. */ > + > +never { > + do > + :: skip; > + :: reader_done != 0 || updater_done != 0 -> break; > + od; > +accept: do > + :: reader_done == 0 || updater_done == 0; > + od; > +} > -- > 1.5.2.5 > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68