Add multicoreverif paper ticketlock and spinlock models
authorMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Sat, 26 Sep 2009 06:53:44 +0000 (02:53 -0400)
committerMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Sat, 26 Sep 2009 06:53:44 +0000 (02:53 -0400)
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
17 files changed:
formal-model/spinlock/DEFINES [new file with mode: 0644]
formal-model/spinlock/Makefile [new file with mode: 0644]
formal-model/spinlock/lock_progress.ltl [new file with mode: 0644]
formal-model/spinlock/mem-progress.spin [new file with mode: 0644]
formal-model/spinlock/mem.sh [new file with mode: 0644]
formal-model/spinlock/mem.spin [new file with mode: 0644]
formal-model/spinlock/refcount.ltl [new file with mode: 0644]
formal-model/spinlock/references.txt [new file with mode: 0644]
formal-model/ticketlock/DEFINES [new file with mode: 0644]
formal-model/ticketlock/Makefile [new file with mode: 0644]
formal-model/ticketlock/config_4_bits_per_byte.define [new file with mode: 0644]
formal-model/ticketlock/lock_progress.ltl [new file with mode: 0644]
formal-model/ticketlock/mem-progress.spin [new file with mode: 0644]
formal-model/ticketlock/mem.sh [new file with mode: 0644]
formal-model/ticketlock/mem.spin [new file with mode: 0644]
formal-model/ticketlock/refcount.ltl [new file with mode: 0644]
formal-model/ticketlock/references.txt [new file with mode: 0644]

diff --git a/formal-model/spinlock/DEFINES b/formal-model/spinlock/DEFINES
new file mode 100644 (file)
index 0000000..4eb5315
--- /dev/null
@@ -0,0 +1 @@
+#define refcount_gt_one (refcount > 1)
diff --git a/formal-model/spinlock/Makefile b/formal-model/spinlock/Makefile
new file mode 100644 (file)
index 0000000..a153e7a
--- /dev/null
@@ -0,0 +1,103 @@
+# 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) Mathieu Desnoyers, 2009
+#
+# Authors: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+
+#CFLAGS=-DSAFETY
+#CFLAGS=-DHASH64 -DREACH
+CFLAGS=-DHASH64
+
+#try pan -i to get the smallest trace.
+
+SPINFILE=mem.spin
+SPINFILE_FAIR=mem-progress.spin
+
+default:
+       make refcount | tee refcount.log
+       make lock_progress | tee lock_progress.log
+       make asserts | tee asserts.log
+       make summary
+
+#show trail : spin -v -t -N pan.ltl input.spin
+# after each individual make.
+
+summary:
+       @echo
+       @echo "Verification summary"
+       @grep error *.log
+
+asserts: clean
+       cat DEFINES > .input.spin
+       cat ${SPINFILE} >> .input.spin
+       rm -f .input.spin.trail
+       spin -a -X .input.spin
+       gcc -w ${CFLAGS} -DSAFETY -o pan pan.c
+       ./pan -v -c1 -X -m10000 -w19
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+refcount: clean refcount_ltl run
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+refcount_ltl:
+       touch .input.define
+       cat DEFINES > pan.ltl
+       cat .input.define >> pan.ltl
+       spin -f "!(`cat refcount.ltl | grep -v ^//`)" >> pan.ltl
+
+lock_progress: clean lock_progress_ltl run_weak_fair
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+lock_progress_ltl:
+       touch .input.define
+       cat .input.define > pan.ltl
+       cat DEFINES >> pan.ltl
+       spin -f "!(`cat lock_progress.ltl | grep -v ^//`)" >> pan.ltl
+
+run: pan
+       ./pan -a -v -c1 -X -m10000 -w19
+
+run_weak_fair: pan_fair
+       ./pan_fair -a -f -v -c1 -X -m10000000 -w20
+
+pan_fair: pan_fair.c
+       gcc -w ${CFLAGS} -o pan_fair pan_fair.c
+
+pan: pan.c
+       gcc -w ${CFLAGS} -o pan pan.c
+
+pan_fair.c: pan.ltl ${SPINFILE_FAIR}
+       cat DEFINES > .input.spin
+       cat .input.define >> .input.spin
+       cat ${SPINFILE_FAIR} >> .input.spin
+       rm -f .input.spin.trail
+       spin -a -X -N pan.ltl .input.spin
+       mv pan.c pan_fair.c
+
+pan.c: pan.ltl ${SPINFILE}
+       cat DEFINES > .input.spin
+       cat .input.define >> .input.spin
+       cat ${SPINFILE} >> .input.spin
+       rm -f .input.spin.trail
+       spin -a -X -N pan.ltl .input.spin
+
+.PHONY: clean default distclean summary
+clean:
+       rm -f pan* trail.out .input.spin* *.spin.trail .input.define
+distclean:
+       rm -f *.trail *.input *.log
diff --git a/formal-model/spinlock/lock_progress.ltl b/formal-model/spinlock/lock_progress.ltl
new file mode 100644 (file)
index 0000000..8718641
--- /dev/null
@@ -0,0 +1 @@
+([] <> !np_)
diff --git a/formal-model/spinlock/mem-progress.spin b/formal-model/spinlock/mem-progress.spin
new file mode 100644 (file)
index 0000000..7930d04
--- /dev/null
@@ -0,0 +1,69 @@
+/*
+ * 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) 2009 Mathieu Desnoyers
+ */
+
+byte lock = 0;
+byte refcount = 0;
+
+inline spin_lock(lock)
+{
+       do
+       :: 1 -> atomic {
+                       if
+                       :: (lock) ->
+                               skip;
+                       :: else ->
+                               lock = 1;
+                               break;
+                       fi;
+               }
+       od;
+}
+
+inline spin_unlock(lock)
+{
+       lock = 0;
+}
+
+proctype proc_A()
+{
+       do
+       :: 1->
+progress_A:
+               spin_lock(lock);
+               refcount = refcount + 1;
+               refcount = refcount - 1;
+               spin_unlock(lock);
+       od;
+}
+
+proctype proc_B()
+{
+       do
+       :: 1->
+               spin_lock(lock);
+               refcount = refcount + 1;
+               refcount = refcount - 1;
+               spin_unlock(lock);
+       od;
+}
+
+init
+{
+       run proc_A();
+       run proc_B();
+}
diff --git a/formal-model/spinlock/mem.sh b/formal-model/spinlock/mem.sh
new file mode 100644 (file)
index 0000000..56e8123
--- /dev/null
@@ -0,0 +1,29 @@
+#!/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
+#               Mathieu Desnoyers, 2009
+#
+# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+#          Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+
+# Basic execution, without LTL clauses. See Makefile.
+
+spin -a mem.spin
+cc -DSAFETY -o pan pan.c
+./pan -v -c1 -X -m10000000 -w21
diff --git a/formal-model/spinlock/mem.spin b/formal-model/spinlock/mem.spin
new file mode 100644 (file)
index 0000000..9e87809
--- /dev/null
@@ -0,0 +1,57 @@
+/*
+ * 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) 2009 Mathieu Desnoyers
+ */
+
+byte lock = 0;
+byte refcount = 0;
+
+inline spin_lock(lock)
+{
+       do
+       :: 1 -> atomic {
+                       if
+                       :: (lock) ->
+                               skip;
+                       :: else ->
+                               lock = 1;
+                               break;
+                       fi;
+               }
+       od;
+}
+
+inline spin_unlock(lock)
+{
+       lock = 0;
+}
+
+proctype proc_X()
+{
+       do
+       :: 1 ->
+               spin_lock(lock);
+               refcount = refcount + 1;
+               refcount = refcount - 1;
+               spin_unlock(lock);
+       od;
+}
+
+init
+{
+       run proc_X();
+       run proc_X();
+}
diff --git a/formal-model/spinlock/refcount.ltl b/formal-model/spinlock/refcount.ltl
new file mode 100644 (file)
index 0000000..48f971f
--- /dev/null
@@ -0,0 +1 @@
+[] (!(refcount_gt_one))
diff --git a/formal-model/spinlock/references.txt b/formal-model/spinlock/references.txt
new file mode 100644 (file)
index 0000000..ca6798f
--- /dev/null
@@ -0,0 +1,7 @@
+http://spinroot.com/spin/Man/ltl.html
+http://en.wikipedia.org/wiki/Linear_temporal_logic
+http://www.dcs.gla.ac.uk/~muffy/MRS4-2002/lect11.ppt
+
+http://www.lsv.ens-cachan.fr/~gastin/ltl2ba/index.php
+http://spinroot.com/spin/Man/index.html
+http://spinroot.com/spin/Man/promela.html
diff --git a/formal-model/ticketlock/DEFINES b/formal-model/ticketlock/DEFINES
new file mode 100644 (file)
index 0000000..4eb5315
--- /dev/null
@@ -0,0 +1 @@
+#define refcount_gt_one (refcount > 1)
diff --git a/formal-model/ticketlock/Makefile b/formal-model/ticketlock/Makefile
new file mode 100644 (file)
index 0000000..c41afd3
--- /dev/null
@@ -0,0 +1,112 @@
+# 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) Mathieu Desnoyers, 2009
+#
+# Authors: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+
+#CFLAGS=-DSAFETY
+#CFLAGS=-DHASH64 -DREACH
+CFLAGS=-DHASH64
+
+#try pan -i to get the smallest trace.
+
+SPINFILE=mem.spin
+SPINFILE_FAIR=mem-progress.spin
+
+default:
+       make refcount | tee refcount.log
+       make refcount_4_bits_per_byte | tee refcount_4_bits_per_byte.log
+       make lock_progress | tee lock_progress.log
+       make lock_progress_4_bits_per_byte | tee lock_progress_4_bits_per_byte.log
+       make asserts | tee asserts.log
+       make summary
+
+#show trail : spin -v -t -N pan.ltl input.spin
+# after each individual make.
+
+summary:
+       @echo
+       @echo "Verification summary"
+       @grep error *.log
+
+asserts: clean
+       cat DEFINES > .input.spin
+       cat ${SPINFILE} >> .input.spin
+       rm -f .input.spin.trail
+       spin -a -X .input.spin
+       gcc -w ${CFLAGS} -DSAFETY -o pan pan.c
+       ./pan -v -c1 -X -m10000000 -w19
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+refcount: clean refcount_ltl run
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+refcount_ltl:
+       touch .input.define
+       cat DEFINES > pan.ltl
+       cat .input.define >> pan.ltl
+       spin -f "!(`cat refcount.ltl | grep -v ^//`)" >> pan.ltl
+
+refcount_4_bits_per_byte: clean refcount_ltl config_4_bits_per_byte_define run
+
+lock_progress: clean lock_progress_ltl run_weak_fair
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+lock_progress_ltl:
+       touch .input.define
+       cat .input.define > pan.ltl
+       cat DEFINES >> pan.ltl
+       spin -f "!(`cat lock_progress.ltl | grep -v ^//`)" >> pan.ltl
+
+lock_progress_4_bits_per_byte: clean lock_progress_ltl config_4_bits_per_byte_define run
+
+config_4_bits_per_byte_define:
+       cp config_4_bits_per_byte.define .input.define
+
+run: pan
+       ./pan -a -v -c1 -X -m1000000 -w19
+
+run_weak_fair: pan_fair
+       ./pan_fair -a -f -v -c1 -X -m1000000 -w20
+
+pan_fair: pan_fair.c
+       gcc -w ${CFLAGS} -DNFAIR=4 -o pan_fair pan_fair.c
+
+pan: pan.c
+       gcc -w ${CFLAGS} -o pan pan.c
+
+pan_fair.c: pan.ltl ${SPINFILE_FAIR}
+       cat DEFINES > .input.spin
+       cat .input.define >> .input.spin
+       cat ${SPINFILE_FAIR} >> .input.spin
+       rm -f .input.spin.trail
+       spin -a -X -N pan.ltl .input.spin
+       mv pan.c pan_fair.c
+
+pan.c: pan.ltl ${SPINFILE}
+       cat DEFINES > .input.spin
+       cat .input.define >> .input.spin
+       cat ${SPINFILE} >> .input.spin
+       rm -f .input.spin.trail
+       spin -a -X -N pan.ltl .input.spin
+
+.PHONY: clean default distclean summary
+clean:
+       rm -f pan* trail.out .input.spin* *.spin.trail .input.define
+distclean:
+       rm -f *.trail *.input *.log
diff --git a/formal-model/ticketlock/config_4_bits_per_byte.define b/formal-model/ticketlock/config_4_bits_per_byte.define
new file mode 100644 (file)
index 0000000..e1d13ca
--- /dev/null
@@ -0,0 +1 @@
+#define CONFIG_BITS_PER_BYTE 4
diff --git a/formal-model/ticketlock/lock_progress.ltl b/formal-model/ticketlock/lock_progress.ltl
new file mode 100644 (file)
index 0000000..8718641
--- /dev/null
@@ -0,0 +1 @@
+([] <> !np_)
diff --git a/formal-model/ticketlock/mem-progress.spin b/formal-model/ticketlock/mem-progress.spin
new file mode 100644 (file)
index 0000000..dad43a4
--- /dev/null
@@ -0,0 +1,98 @@
+/*
+ * 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) 2009 Mathieu Desnoyers
+ */
+
+/* 16 CPUs max (byte has 8 bits, divided in two) */
+
+#ifndef CONFIG_BITS_PER_BYTE
+#define BITS_PER_BYTE          8
+#else
+// test progress failure with shorter byte size. Will fail with 5 proc.
+#define BITS_PER_BYTE          CONFIG_BITS_PER_BYTE
+#endif
+
+#define HBPB                   (BITS_PER_BYTE / 2)     /* 4 */
+#define HMASK                  ((1 << HBPB) - 1)       /* 0x0F */
+
+/* for byte type */
+#define LOW_HALF(val)          ((val) & HMASK)
+#define LOW_HALF_INC           1
+
+#define HIGH_HALF(val)         ((val) & (HMASK << HBPB))
+#define HIGH_HALF_INC          (1 << HBPB)
+
+byte lock = 0;
+byte refcount = 0;
+
+inline spin_lock(lock, ticket)
+{
+       atomic {
+               ticket = HIGH_HALF(lock) >> HBPB;
+               lock = lock + HIGH_HALF_INC;    /* overflow expected */
+       }
+
+       do
+       :: 1 ->
+               if
+               :: (LOW_HALF(lock) == ticket) ->
+                       break;
+               :: else ->
+                       skip;
+               fi;
+       od;
+}
+
+inline spin_unlock(lock)
+{
+       lock = HIGH_HALF(lock) | LOW_HALF(lock + LOW_HALF_INC);
+}
+
+proctype proc_A()
+{
+       byte ticket;
+
+       do
+       :: 1 ->
+progress_A:
+               spin_lock(lock, ticket);
+               refcount = refcount + 1;
+               refcount = refcount - 1;
+               spin_unlock(lock);
+       od;
+}
+
+proctype proc_B()
+{
+       byte ticket;
+
+       do
+       :: 1 ->
+               spin_lock(lock, ticket);
+               refcount = refcount + 1;
+               refcount = refcount - 1;
+               spin_unlock(lock);
+       od;
+}
+
+init
+{
+       run proc_A();
+       run proc_B();
+       run proc_B();
+       run proc_B();
+       run proc_B();
+}
diff --git a/formal-model/ticketlock/mem.sh b/formal-model/ticketlock/mem.sh
new file mode 100644 (file)
index 0000000..56e8123
--- /dev/null
@@ -0,0 +1,29 @@
+#!/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
+#               Mathieu Desnoyers, 2009
+#
+# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+#          Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+
+# Basic execution, without LTL clauses. See Makefile.
+
+spin -a mem.spin
+cc -DSAFETY -o pan pan.c
+./pan -v -c1 -X -m10000000 -w21
diff --git a/formal-model/ticketlock/mem.spin b/formal-model/ticketlock/mem.spin
new file mode 100644 (file)
index 0000000..445ee9a
--- /dev/null
@@ -0,0 +1,83 @@
+/*
+ * 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) 2009 Mathieu Desnoyers
+ */
+
+/* 16 CPUs max (byte has 8 bits, divided in two) */
+
+#ifndef CONFIG_BITS_PER_BYTE
+#define BITS_PER_BYTE          8
+#else
+#define BITS_PER_BYTE          CONFIG_BITS_PER_BYTE
+#endif
+
+#define HBPB                   (BITS_PER_BYTE / 2)     /* 4 */
+#define HMASK                  ((1 << HBPB) - 1)       /* 0x0F */
+
+/* for byte type */
+#define LOW_HALF(val)          ((val) & HMASK)
+#define LOW_HALF_INC           1
+
+#define HIGH_HALF(val)         ((val) & (HMASK << HBPB))
+#define HIGH_HALF_INC          (1 << HBPB)
+
+byte lock = 0;
+byte refcount = 0;
+
+inline spin_lock(lock, ticket)
+{
+       atomic {
+               ticket = HIGH_HALF(lock) >> HBPB;
+               lock = lock + HIGH_HALF_INC;    /* overflow expected */
+       }
+
+       do
+       :: 1 ->
+               if
+               :: (LOW_HALF(lock) == ticket) ->
+                       break;
+               :: else ->
+                       skip;
+               fi;
+       od;
+}
+
+inline spin_unlock(lock)
+{
+       lock = HIGH_HALF(lock) | LOW_HALF(lock + LOW_HALF_INC);
+}
+
+proctype proc_X()
+{
+       byte ticket;
+
+       do
+       :: 1->
+               spin_lock(lock, ticket);
+               refcount = refcount + 1;
+               refcount = refcount - 1;
+               spin_unlock(lock);
+       od;
+}
+
+init
+{
+       run proc_X();
+       run proc_X();
+       run proc_X();
+       run proc_X();
+       run proc_X();
+}
diff --git a/formal-model/ticketlock/refcount.ltl b/formal-model/ticketlock/refcount.ltl
new file mode 100644 (file)
index 0000000..48f971f
--- /dev/null
@@ -0,0 +1 @@
+[] (!(refcount_gt_one))
diff --git a/formal-model/ticketlock/references.txt b/formal-model/ticketlock/references.txt
new file mode 100644 (file)
index 0000000..ca6798f
--- /dev/null
@@ -0,0 +1,7 @@
+http://spinroot.com/spin/Man/ltl.html
+http://en.wikipedia.org/wiki/Linear_temporal_logic
+http://www.dcs.gla.ac.uk/~muffy/MRS4-2002/lect11.ppt
+
+http://www.lsv.ens-cachan.fr/~gastin/ltl2ba/index.php
+http://spinroot.com/spin/Man/index.html
+http://spinroot.com/spin/Man/promela.html
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