X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=mpmc-queue%2Fmpmc-queue.h;h=fa5f37a1cf054634bdb4d9c152ef7299ed7f6b63;hb=1438eb7c0715e53611a717e593bfa3fe1bd30588;hp=f73ab992e0b1fcfbbf962b067c204cdb75b9578f;hpb=ca67665a06590d48352fd2c601004a39bd993ca8;p=model-checker-benchmarks.git

diff --git a/mpmc-queue/mpmc-queue.h b/mpmc-queue/mpmc-queue.h
index f73ab99..fa5f37a 100644
--- a/mpmc-queue/mpmc-queue.h
+++ b/mpmc-queue/mpmc-queue.h
@@ -27,6 +27,8 @@ public:
 	//-----------------------------------------------------
 
 	t_element * read_fetch() {
+		// FIXME: We can have a relaxed for sure here since the next CAS
+		// will fix the problem
 		unsigned int rdwr = m_rdwr.load(mo_acquire);
 		unsigned int rd,wr;
 		for(;;) {
@@ -34,16 +36,18 @@ public:
 			wr = rdwr & 0xFFFF;
 
 			if ( wr == rd ) // empty
-				return false;
-
+				return NULL;
+	
 			if ( m_rdwr.compare_exchange_weak(rdwr,rdwr+(1<<16),mo_acq_rel) )
 				break;
+			else
+				thrd_yield();
 		}
 
 		// (*1)
 		rl::backoff bo;
 		while ( (m_written.load(mo_acquire) & 0xFFFF) != wr ) {
-			bo.yield();
+			thrd_yield();
 		}
 
 		t_element * p = & ( m_array[ rd % t_size ] );
@@ -58,6 +62,8 @@ public:
 	//-----------------------------------------------------
 
 	t_element * write_prepare() {
+		// FIXME: We can have a relaxed for sure here since the next CAS
+		// will fix the problem
 		unsigned int rdwr = m_rdwr.load(mo_acquire);
 		unsigned int rd,wr;
 		for(;;) {
@@ -69,12 +75,14 @@ public:
 
 			if ( m_rdwr.compare_exchange_weak(rdwr,(rd<<16) | ((wr+1)&0xFFFF),mo_acq_rel) )
 				break;
+			else
+				thrd_yield();
 		}
 
 		// (*1)
 		rl::backoff bo;
 		while ( (m_read.load(mo_acquire) & 0xFFFF) != rd ) {
-			bo.yield();
+			thrd_yield();
 		}
 
 		t_element * p = & ( m_array[ wr % t_size ] );