Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH URCU formal] Add liveness checks to user-level RCU model. | Date | Fri, 20 Feb 2009 09:39:27 -0800 |
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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 <paulmck@linux.vnet.ibm.com> --- 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 <paulmck@linux.vnet.ibm.com> + 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
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