From cc76fd1df9192f5bf2e10113bda65e25251075c8 Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Fri, 27 Feb 2009 14:13:12 -0500
Subject: [PATCH] Add remote barrier model

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
 formal-model/urcu/DEFINES   |  2 ++
 formal-model/urcu/urcu.spin | 64 +++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/formal-model/urcu/DEFINES b/formal-model/urcu/DEFINES
index e1fb32c..843d135 100644
--- a/formal-model/urcu/DEFINES
+++ b/formal-model/urcu/DEFINES
@@ -7,3 +7,5 @@
 #ifndef READER_NEST_LEVEL
 #define READER_NEST_LEVEL 2
 #endif
+
+#define REMOTE_BARRIERS
diff --git a/formal-model/urcu/urcu.spin b/formal-model/urcu/urcu.spin
index 903782b..2282407 100644
--- a/formal-model/urcu/urcu.spin
+++ b/formal-model/urcu/urcu.spin
@@ -80,6 +80,68 @@
 	:: 1 -> skip			\
 	fi;
 
+/*
+ * Remote barriers tests the scheme where a signal (or IPI) is sent to all
+ * reader threads to promote their compiler barrier to a smp_mb().
+ */
+#ifdef REMOTE_BARRIERS
+
+inline smp_rmb_pid(i)
+{
+	atomic {
+		CACHE_READ_FROM_MEM(urcu_gp_ctr, i);
+		CACHE_READ_FROM_MEM(urcu_active_readers_one, i);
+		CACHE_READ_FROM_MEM(generation_ptr, i);
+	}
+}
+
+inline smp_wmb_pid(i)
+{
+	atomic {
+		CACHE_WRITE_TO_MEM(urcu_gp_ctr, i);
+		CACHE_WRITE_TO_MEM(urcu_active_readers_one, i);
+		CACHE_WRITE_TO_MEM(generation_ptr, i);
+	}
+}
+
+inline smp_mb_pid(i)
+{
+	atomic {
+#ifndef NO_WMB
+		smp_wmb_pid(i);
+#endif
+#ifndef NO_RMB
+		smp_rmb_pid(i);
+#endif
+		skip;
+	}
+}
+
+/*
+ * Readers do a simple barrier(), writers are doing a smp_mb() _and_ sending a
+ * signal or IPI to have all readers execute a smp_mb.
+ * We are not modeling the whole rendez-vous between readers and writers here,
+ * we just let the writer update each reader's caches remotely.
+ */
+inline smp_mb(i)
+{
+	if
+	:: get_pid() >= NR_READERS ->
+		smp_mb_pid(get_pid());
+		i = 0;
+		do
+		:: i < NR_READERS ->
+			smp_mb_pid(i);
+			i++;
+		:: i >= NR_READERS -> break
+		od;
+		smp_mb_pid(get_pid());
+	:: else -> skip;
+	fi;
+}
+
+#else
+
 inline smp_rmb(i)
 {
 	atomic {
@@ -111,6 +173,8 @@ inline smp_mb(i)
 	}
 }
 
+#endif
+
 /* Keep in sync manually with smp_rmb, wmp_wmb and ooo_mem */
 DECLARE_CACHED_VAR(byte, urcu_gp_ctr, 1);
 /* Note ! currently only one reader */
-- 
2.34.1