Check double write read order
authorMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Mon, 6 Apr 2009 20:30:04 +0000 (16:30 -0400)
committerMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Mon, 6 Apr 2009 20:30:04 +0000 (16:30 -0400)
Check the following scenario :

> > P.S.:  Regarding very weak memory-ordering models, I recall that in our
> > earlier discussions we considered this scenario:

> >     CPU 0                   CPU 1
> >     -----                   -----
> >     x = 1;                  y = 1;
> >     mb();                   mb();
> >     read y                  read x

> > with the question being whether it was possible for both reads to
> > obtain the value 0.  With sufficiently weak ordering it is possible,
> > but it turned out that there are places in the Linux kernel (I don't
> > remember where) that essentially assume this cannot happen.  Have you
> > gotten far enough in your outline of the semi-formal model to address
> > this sort of question?

formal-model/ooomem-double-update/DEFINES [new file with mode: 0644]
formal-model/ooomem-double-update/Makefile [new file with mode: 0644]
formal-model/ooomem-double-update/mem.sh [new file with mode: 0644]
formal-model/ooomem-double-update/mem.spin [new file with mode: 0644]
formal-model/ooomem-double-update/read_order.ltl [new file with mode: 0644]
formal-model/ooomem-double-update/read_order_no_rmb.define [new file with mode: 0644]
formal-model/ooomem-double-update/read_order_no_wmb.define [new file with mode: 0644]
formal-model/ooomem-double-update/references.txt [new file with mode: 0644]

diff --git a/formal-model/ooomem-double-update/DEFINES b/formal-model/ooomem-double-update/DEFINES
new file mode 100644 (file)
index 0000000..e74150d
--- /dev/null
@@ -0,0 +1,2 @@
+#define read_one_is_zero (read_one == 0)
+#define read_two_is_zero (read_two == 0)
diff --git a/formal-model/ooomem-double-update/Makefile b/formal-model/ooomem-double-update/Makefile
new file mode 100644 (file)
index 0000000..09107bc
--- /dev/null
@@ -0,0 +1,92 @@
+# 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
+
+#try pan -i to get the smallest trace.
+
+SPINFILE=mem.spin
+
+default:
+       make read_order | tee read_order.log
+       make read_order_no_wmb | tee read_order_no_wmb.log
+       make read_order_no_rmb | tee read_order_no_rmb.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 -i -v -c1 -X -m10000 -w19
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+read_order: clean read_order_ltl run
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+read_order_no_rmb: clean read_order_ltl read_order_no_rmb_define run
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+read_order_no_rmb_define:
+       cp read_order_no_rmb.define .input.define
+
+read_order_no_wmb: clean read_order_ltl read_order_no_wmb_define run
+       cp .input.spin $@.spin.input
+       -cp .input.spin.trail $@.spin.input.trail
+
+read_order_no_wmb_define:
+       cp read_order_no_wmb.define .input.define
+
+read_order_ltl:
+       touch .input.define
+       cat DEFINES > pan.ltl
+       cat .input.define >> pan.ltl
+       spin -f "!(`cat read_order.ltl | grep -v ^//`)" >> pan.ltl
+
+run: pan
+       ./pan -a -i -v -c1 -X -m10000 -w19
+
+pan: pan.c
+       gcc -w ${CFLAGS} -o pan pan.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/ooomem-double-update/mem.sh b/formal-model/ooomem-double-update/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/ooomem-double-update/mem.spin b/formal-model/ooomem-double-update/mem.spin
new file mode 100644 (file)
index 0000000..4c5d6fd
--- /dev/null
@@ -0,0 +1,167 @@
+/*
+ * mem.spin: Promela code to validate memory barriers with OOO memory.
+ *
+ * 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
+ */
+
+/* Promela validation variables. */
+
+#define NR_READERS 1
+#define NR_WRITERS 1
+
+#define NR_PROCS 2
+
+#define get_pid()      (_pid)
+
+/*
+ * Each process have its own data in cache. Caches are randomly updated.
+ * smp_wmb and smp_rmb forces cache updates (write and read), wmb_mb forces
+ * both.
+ */
+
+#define DECLARE_CACHED_VAR(type, x, v) \
+       type mem_##x = v;               \
+       type cached_##x[NR_PROCS] = v;  \
+       bit cache_dirty_##x[NR_PROCS] = 0
+
+#define IS_CACHE_DIRTY(x, id)  (cache_dirty_##x[id])
+
+#define READ_CACHED_VAR(x)     (cached_##x[get_pid()])
+
+#define WRITE_CACHED_VAR(x, v)         \
+       atomic {                        \
+               cached_##x[get_pid()] = v;      \
+               cache_dirty_##x[get_pid()] = 1; \
+       }
+
+#define CACHE_WRITE_TO_MEM(x, id)              \
+       if                                      \
+       :: IS_CACHE_DIRTY(x, id) ->             \
+               mem_##x = cached_##x[id];       \
+               cache_dirty_##x[id] = 0;        \
+       :: else ->                              \
+               skip                            \
+       fi;
+
+#define CACHE_READ_FROM_MEM(x, id)     \
+       if                              \
+       :: !IS_CACHE_DIRTY(x, id) ->    \
+               cached_##x[id] = mem_##x;\
+       :: else ->                      \
+               skip                    \
+       fi;
+
+/*
+ * May update other caches if cache is dirty, or not.
+ */
+#define RANDOM_CACHE_WRITE_TO_MEM(x, id)\
+       if                              \
+       :: 1 -> CACHE_WRITE_TO_MEM(x, id);      \
+       :: 1 -> skip                    \
+       fi;
+
+#define RANDOM_CACHE_READ_FROM_MEM(x, id)\
+       if                              \
+       :: 1 -> CACHE_READ_FROM_MEM(x, id);     \
+       :: 1 -> skip                    \
+       fi;
+
+inline smp_rmb()
+{
+       atomic {
+               CACHE_READ_FROM_MEM(alpha, get_pid());
+               CACHE_READ_FROM_MEM(beta, get_pid());
+       }
+}
+
+inline smp_wmb()
+{
+       atomic {
+               CACHE_WRITE_TO_MEM(alpha, get_pid());
+               CACHE_WRITE_TO_MEM(beta, get_pid());
+       }
+}
+
+inline smp_mb()
+{
+       atomic {
+               smp_wmb();
+               smp_rmb();
+       }
+}
+
+/* Keep in sync manually with smp_rmb, wmp_wmb and ooo_mem */
+DECLARE_CACHED_VAR(byte, alpha, 0);
+DECLARE_CACHED_VAR(byte, beta, 0);
+
+inline ooo_mem()
+{
+       atomic {
+               RANDOM_CACHE_WRITE_TO_MEM(alpha, get_pid());
+               RANDOM_CACHE_WRITE_TO_MEM(beta, get_pid());
+               RANDOM_CACHE_READ_FROM_MEM(alpha, get_pid());
+               RANDOM_CACHE_READ_FROM_MEM(beta, get_pid());
+       }
+}
+
+/* value 2 is uninitialized */
+byte read_one = 2;
+byte read_two = 2;
+
+active proctype test_proc_one()
+{
+       assert(get_pid() < NR_PROCS);
+
+       ooo_mem();
+       WRITE_CACHED_VAR(alpha, 1);
+       ooo_mem();
+#ifndef NO_WMB
+       smp_wmb();
+       ooo_mem();
+#endif
+#ifndef NO_RMB
+       smp_rmb();
+       ooo_mem();
+#endif
+       read_one = READ_CACHED_VAR(beta);
+       ooo_mem();
+       // test : [] (read_one == 0 -> read_two != 0)
+       // test : [] (read_two == 0 -> read_one != 0)
+       assert(!(read_one == 0 && read_two == 0));
+}
+
+active proctype test_proc_two()
+{
+       assert(get_pid() < NR_PROCS);
+
+       ooo_mem();
+       WRITE_CACHED_VAR(beta, 1);
+       ooo_mem();
+#ifndef NO_WMB
+       smp_wmb();
+       ooo_mem();
+#endif
+#ifndef NO_RMB
+       smp_rmb();
+       ooo_mem();
+#endif
+       read_two = READ_CACHED_VAR(alpha);
+       ooo_mem();
+       // test : [] (read_one == 0 -> read_two != 0)
+       // test : [] (read_two == 0 -> read_one != 0)
+       assert(!(read_one == 0 && read_two == 0));
+}
diff --git a/formal-model/ooomem-double-update/read_order.ltl b/formal-model/ooomem-double-update/read_order.ltl
new file mode 100644 (file)
index 0000000..f4dbf03
--- /dev/null
@@ -0,0 +1 @@
+[] (read_one_is_zero -> !read_two_is_zero)
diff --git a/formal-model/ooomem-double-update/read_order_no_rmb.define b/formal-model/ooomem-double-update/read_order_no_rmb.define
new file mode 100644 (file)
index 0000000..73e61a4
--- /dev/null
@@ -0,0 +1 @@
+#define NO_RMB
diff --git a/formal-model/ooomem-double-update/read_order_no_wmb.define b/formal-model/ooomem-double-update/read_order_no_wmb.define
new file mode 100644 (file)
index 0000000..710f29d
--- /dev/null
@@ -0,0 +1 @@
+#define NO_WMB
diff --git a/formal-model/ooomem-double-update/references.txt b/formal-model/ooomem-double-update/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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