From f8c46d903b303b81ef0d25cb8495de22d299466b Mon Sep 17 00:00:00 2001
From: Peizhao Ou <peizhaoo@uci.edu>
Date: Thu, 12 Feb 2015 18:26:01 -0800
Subject: [PATCH] changes to seqlock

---
 Makefile                   | 2 +-
 seqlock/seqlock-wildcard.h | 3 +--
 seqlock/seqlock.c          | 4 ++--
 seqlock/seqlock.h          | 9 ++++-----
 seqlock/testcase1.c        | 5 +++--
 5 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index 835f7d1..b681de1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 DIRS := barrier mcs-lock mpmc-queue spsc-queue spsc-bugfix linuxrwlocks \
 	dekker-fences chase-lev-deque ms-queue chase-lev-deque-bugfix \
-	concurrent-hashmap
+	concurrent-hashmap seqlock
 
 .PHONY: $(DIRS)
 
diff --git a/seqlock/seqlock-wildcard.h b/seqlock/seqlock-wildcard.h
index 85686ea..62b7583 100644
--- a/seqlock/seqlock-wildcard.h
+++ b/seqlock/seqlock-wildcard.h
@@ -27,9 +27,8 @@ typedef struct seqlock {
 	}
 	
 	void write(int new_data) {
+		int old_seq = _seq.load(wildcard(4)); // acquire
 		while (true) {
-			// This might be a relaxed too
-			int old_seq = _seq.load(wildcard(4)); // acquire
 			if (old_seq % 2 == 1)
 				continue; // Retry
 
diff --git a/seqlock/seqlock.c b/seqlock/seqlock.c
index d2e33b8..146239f 100644
--- a/seqlock/seqlock.c
+++ b/seqlock/seqlock.c
@@ -22,11 +22,11 @@ int user_main(int argc, char **argv) {
 	lock = new seqlock_t();
 
 	thrd_create(&t1, (thrd_start_t)&a, NULL);
-	thrd_create(&t2, (thrd_start_t)&b, NULL);
+	//thrd_create(&t2, (thrd_start_t)&b, NULL);
 	thrd_create(&t3, (thrd_start_t)&c, NULL);
 
 	thrd_join(t1);
-	thrd_join(t2);
+	//thrd_join(t2);
 	thrd_join(t3);
 	return 0;
 }
diff --git a/seqlock/seqlock.h b/seqlock/seqlock.h
index f263bec..c5a965c 100644
--- a/seqlock/seqlock.h
+++ b/seqlock/seqlock.h
@@ -17,7 +17,7 @@ typedef struct seqlock {
 			int old_seq = _seq.load(memory_order_acquire); // acquire
 			if (old_seq % 2 == 1) continue;
 
-			int res = _data.load(memory_order_acquire); // acquire
+			int res = _data.load(memory_order_acquire); 
 			if (_seq.load(memory_order_relaxed) == old_seq) { // relaxed
 				return res;
 			}
@@ -25,20 +25,19 @@ typedef struct seqlock {
 	}
 	
 	void write(int new_data) {
+		int old_seq = _seq.load(memory_order_acquire); // acquire
 		while (true) {
 			// This might be a relaxed too
-			int old_seq = _seq.load(memory_order_acquire); // acquire
 			if (old_seq % 2 == 1)
 				continue; // Retry
 
-			// Should be relaxed!!! 
 			if (_seq.compare_exchange_strong(old_seq, old_seq + 1,
-				memory_order_relaxed, memory_order_relaxed)) // relaxed 
+				memory_order_acq_rel, memory_order_acquire)) 
 				break;
 		}
 
 		// Update the data
-		_data.store(new_data, memory_order_release); // release
+		_data.store(new_data, memory_order_release); // Can be relaxed
 
 		_seq.fetch_add(1, memory_order_release); // release
 	}
diff --git a/seqlock/testcase1.c b/seqlock/testcase1.c
index 6417db3..8441972 100644
--- a/seqlock/testcase1.c
+++ b/seqlock/testcase1.c
@@ -14,6 +14,7 @@ static void b(void *obj) {
 }
 
 static void c(void *obj) {
+	lock->write(2);
 	int r1 = lock->read();
 }
 
@@ -22,11 +23,11 @@ int user_main(int argc, char **argv) {
 	lock = new seqlock_t();
 
 	thrd_create(&t1, (thrd_start_t)&a, NULL);
-	thrd_create(&t2, (thrd_start_t)&b, NULL);
+	//thrd_create(&t2, (thrd_start_t)&b, NULL);
 	thrd_create(&t3, (thrd_start_t)&c, NULL);
 
 	thrd_join(t1);
-	thrd_join(t2);
+	//thrd_join(t2);
 	thrd_join(t3);
 	return 0;
 }
-- 
2.34.1