X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=mpmc-queue%2Fmpmc-queue.h;h=fa5f37a1cf054634bdb4d9c152ef7299ed7f6b63;hb=1438eb7c0715e53611a717e593bfa3fe1bd30588;hp=fdfbb365164a0ab8ef0ab87e75b044b62cae6388;hpb=3f557d137e70ca9da76ce84ec663da53e266e272;p=model-checker-benchmarks.git

diff --git a/mpmc-queue/mpmc-queue.h b/mpmc-queue/mpmc-queue.h
index fdfbb36..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;
-
-			if ( m_rdwr.compare_exchange(rdwr,rdwr+(1<<16),mo_acq_rel) )
+				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(;;) {
@@ -67,14 +73,16 @@ public:
 			if ( wr == ((rd + t_size)&0xFFFF) ) // full
 				return NULL;
 
-			if ( m_rdwr.compare_exchange(rdwr,(rd<<16) | ((wr+1)&0xFFFF),mo_acq_rel) )
+			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 ] );