From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Mon, 23 Feb 2009 07:02:54 +0000 (-0500)
Subject: dual writer fix
X-Git-Tag: v0.1~276
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=710b09b7ba5203ea868240c1746d0ac0fc65f884;p=userspace-rcu.git

dual writer fix

Make mutex between writers really atomic. Fixes the two flips run.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---

diff --git a/formal-model/urcu/Makefile b/formal-model/urcu/Makefile
index 7802c7f..7b395cb 100644
--- a/formal-model/urcu/Makefile
+++ b/formal-model/urcu/Makefile
@@ -44,7 +44,7 @@ asserts: clean
 	rm -f .input.spin.trail
 	spin -a -X .input.spin
 	gcc -w ${CFLAGS} -DSAFETY -o pan pan.c
-	./pan -v -c1 -X -m10000 -w19
+	./pan -v -c1 -X -m10000 -w20
 	cp .input.spin $@.spin.input
 	-cp .input.spin.trail $@.spin.input.trail
 
@@ -87,7 +87,7 @@ urcu_free_ltl:
 	spin -f "!(`cat urcu_free.ltl | grep -v ^//`)" >> pan.ltl
 
 run: pan
-	./pan -a -v -c1 -X -m10000 -w19
+	./pan -a -v -c1 -X -m10000 -w20
 
 pan: pan.c
 	gcc -w ${CFLAGS} -o pan pan.c
diff --git a/formal-model/urcu/urcu.spin b/formal-model/urcu/urcu.spin
index 7f94d3b..5ac2f02 100644
--- a/formal-model/urcu/urcu.spin
+++ b/formal-model/urcu/urcu.spin
@@ -225,11 +225,16 @@ active [NR_WRITERS] proctype urcu_writer()
 	ooo_mem(i);
 
 	do
-	:: write_lock == 0 ->
-		write_lock = 1;
-		break;
-	:: else ->
-		skip;
+	:: 1 ->
+		atomic {
+			if
+			:: write_lock == 0 ->
+				write_lock = 1;
+				break;
+			:: else ->
+				skip;
+			fi;
+		}
 	od;
 	smp_mb(i);
 	ooo_mem(i);
@@ -251,11 +256,11 @@ active [NR_WRITERS] proctype urcu_writer()
 #endif
 	ooo_mem(i);
 	smp_mb(i);
-	/* free-up step, e.g., kfree(). */
 	ooo_mem(i);
+	write_lock = 0;
+	/* free-up step, e.g., kfree(). */
 	atomic {
 		last_free_gen = old_gen;
 		free_done = 1;
-		write_lock = 0;
 	}
 }