From: Peizhao Ou <peizhaoo@uci.edu>
Date: Thu, 12 Feb 2015 06:34:47 +0000 (-0800)
Subject: changes
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=0487e29583033894529edd8c8e20291aa5eefbb6;p=model-checker-benchmarks.git

changes
---

diff --git a/mcs-lock/Makefile b/mcs-lock/Makefile
index 5a311b3..51f9891 100644
--- a/mcs-lock/Makefile
+++ b/mcs-lock/Makefile
@@ -2,10 +2,16 @@ include ../benchmarks.mk
 
 TESTNAME = mcs-lock
 
-all: $(TESTNAME)
+WILDCARD_TESTS = testcase1
+
+all: $(TESTNAME) $(WILDCARD_TESTS)
+	echo $^
 
 $(TESTNAME): $(TESTNAME).cc $(TESTNAME).h
 	$(CXX) -o $@ $< $(CXXFLAGS) $(LDFLAGS)
 
+$(WILDCARD_TESTS): % : %.cc $(TESTNAME)-wildcard.h
+	$(CXX) -o $@ $< $(CXXFLAGS) $(LDFLAGS)
+
 clean:
-	rm -f $(TESTNAME) *.o
+	rm -f $(TESTNAME) *.o $(WILDCARD_TESTS) 
diff --git a/mcs-lock/mcs-lock-wildcard.h b/mcs-lock/mcs-lock-wildcard.h
new file mode 100644
index 0000000..b8d92b2
--- /dev/null
+++ b/mcs-lock/mcs-lock-wildcard.h
@@ -0,0 +1,103 @@
+// mcs on stack
+
+#include <stdatomic.h>
+#include <unrelacy.h>
+#include "wildcard.h" 
+
+
+struct mcs_node {
+	std::atomic<mcs_node *> next;
+	std::atomic<int> gate;
+
+	mcs_node() {
+		next.store(0);
+		gate.store(0);
+	}
+};
+
+struct mcs_mutex {
+public:
+	// tail is null when lock is not held
+	std::atomic<mcs_node *> m_tail;
+
+	mcs_mutex() {
+		m_tail.store( NULL);
+	}
+	~mcs_mutex() {
+		//ASSERT( m_tail.load() == NULL );
+	}
+
+	// Each thread will have their own guard.
+	class guard {
+	public:
+		mcs_mutex * m_t;
+		mcs_node    m_node; // node held on the stack
+
+		guard(mcs_mutex * t) : m_t(t) { t->lock(this); }
+		~guard() { m_t->unlock(this); }
+	};
+
+	void lock(guard * I) {
+		mcs_node * me = &(I->m_node);
+
+		// set up my node :
+		// not published yet so relaxed :
+		me->next.store(NULL, wildcard(1) ); // relaxed
+		me->gate.store(1, wildcard(2) ); // relaxed
+
+		// publish my node as the new tail :
+		mcs_node * pred = m_tail.exchange(me, wildcard(3)); // acq_rel
+		if ( pred != NULL ) {
+			// (*1) race here
+			// unlock of pred can see me in the tail before I fill next
+
+			// publish me to previous lock-holder :
+			pred->next.store(me, wildcard(4) ); // release
+
+			// (*2) pred not touched any more       
+
+			// now this is the spin -
+			// wait on predecessor setting my flag -
+			rl::linear_backoff bo;
+			int my_gate = 1;
+			while ( (my_gate = me->gate.load(wildcard(5))) ) { // acquire
+				thrd_yield();
+			}
+		}
+	}
+
+	void unlock(guard * I) {
+		mcs_node * me = &(I->m_node);
+
+		mcs_node * next = me->next.load(wildcard(6)); // acquire
+		if ( next == NULL )
+		{
+			mcs_node * tail_was_me = me;
+			bool success;
+			// FIXME: SCFence infers acq_rel / release
+			// Could be release if wildcard(8) is acquire
+			if ( (success = m_tail.compare_exchange_strong(
+				tail_was_me,NULL,wildcard(7))) ) { // acq_rel
+				// got null in tail, mutex is unlocked
+				return;
+			}
+
+			// (*1) catch the race :
+			rl::linear_backoff bo;
+			for(;;) {
+				// FIXME: SCFence infers relaxed / acquire
+				// Could be relaxed if wildcard(7) is acq_rel
+				next = me->next.load(wildcard(8)); // acquire
+				if ( next != NULL )
+					break;
+				thrd_yield();
+			}
+		}
+
+		// (*2) - store to next must be done,
+		//  so no locker can be viewing my node any more        
+
+		// let next guy in :
+		next->gate.store( 0, wildcard(9) ); // release
+	}
+};
diff --git a/mcs-lock/testcase1.cc b/mcs-lock/testcase1.cc
new file mode 100644
index 0000000..971bf1d
--- /dev/null
+++ b/mcs-lock/testcase1.cc
@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <threads.h>
+
+#include "mcs-lock-wildcard.h"
+
+/* For data race instrumentation */
+#include "librace.h"
+
+struct mcs_mutex *mutex;
+static uint32_t shared;
+
+void threadA(void *arg)
+{
+	mcs_mutex::guard g(mutex);
+	printf("store: %d\n", 17);
+	store_32(&shared, 17);
+	mutex->unlock(&g);
+	mutex->lock(&g);
+	printf("load: %u\n", load_32(&shared));
+}
+
+void threadB(void *arg)
+{
+	mcs_mutex::guard g(mutex);
+	printf("load: %u\n", load_32(&shared));
+	mutex->unlock(&g);
+	mutex->lock(&g);
+	printf("store: %d\n", 17);
+	store_32(&shared, 17);
+}
+
+int user_main(int argc, char **argv)
+{
+	thrd_t A, B;
+
+	mutex = new mcs_mutex();
+
+	thrd_create(&A, &threadA, NULL);
+	thrd_create(&B, &threadB, NULL);
+	thrd_join(A);
+	thrd_join(B);
+	return 0;
+}