ck_rwlock: Ditch ck_rwlock latch for ck_swlock.

include/ck_rwlock.h

@@ -233,6 +233,7 @@ ck_rwlock_read_latchlock(ck_rwlock_t *rw)
 				snapshot = ck_pr_load_32(&rw->n_readers);
 			} while (snapshot >> CK_RWLOCK_LATCH_SHIFT);
 
+			ck_pr_cas_32(&rw->n_readers, snapshot + 1, snapshot);
 			continue;
 		} 
 

regressions/ck_rwlock/validate/Makefile

@@ -14,4 +14,4 @@ clean:
 	rm -rf *.dSYM *.exe *~ *.o $(OBJECTS)
 
 include ../../../build/regressions.build
-CFLAGS+=$(PTHREAD_CFLAGS) -D_GNU_SOURCE
+CFLAGS+=$(PTHREAD_CFLAGS) -D_GNU_SOURCE -O0

regressions/ck_rwlock/validate/validate.c

@@ -333,6 +333,55 @@ thread_rtm(void *null CK_CC_UNUSED)
 }
 #endif /* CK_F_PR_RTM */
 
+static void *
+thread_latch(void *null CK_CC_UNUSED)
+{
+	unsigned int i = ITERATE;
+	unsigned int l;
+
+        if (aff_iterate(&a)) {
+                perror("ERROR: Could not affine thread");
+                exit(EXIT_FAILURE);
+        }
+
+	while (i--) {
+		ck_rwlock_write_lock(&lock);
+		ck_rwlock_write_latch(&lock);
+		{
+			ck_pr_inc_uint(&locked);
+			ck_pr_inc_uint(&locked);
+			ck_pr_inc_uint(&locked);
+			ck_pr_inc_uint(&locked);
+			ck_pr_inc_uint(&locked);
+			ck_pr_inc_uint(&locked);
+			ck_pr_inc_uint(&locked);
+			ck_pr_inc_uint(&locked);
+
+			ck_pr_dec_uint(&locked);
+			ck_pr_dec_uint(&locked);
+			ck_pr_dec_uint(&locked);
+			ck_pr_dec_uint(&locked);
+			ck_pr_dec_uint(&locked);
+			ck_pr_dec_uint(&locked);
+			ck_pr_dec_uint(&locked);
+			ck_pr_dec_uint(&locked);
+		}
+		ck_rwlock_write_unlatch(&lock);
+		ck_rwlock_write_unlock(&lock);
+
+		ck_rwlock_read_latchlock(&lock);
+		{
+			l = ck_pr_load_uint(&locked);
+			if (l != 0) {
+				ck_error("ERROR [RD:%d]: %u != 0\n", __LINE__, l);
+			}
+		}
+		ck_rwlock_read_unlock(&lock);
+	}
+
+	return (NULL);
+}
+
 static void *
 thread(void *null CK_CC_UNUSED)
 {
@@ -436,6 +485,7 @@ main(int argc, char *argv[])
 	a.delta = atoi(argv[2]);
 
 	rwlock_test(threads, thread, "regular");
+	rwlock_test(threads, thread_latch, "latch");
 #ifdef CK_F_PR_RTM
 	rwlock_test(threads, thread_rtm, "rtm");
 	rwlock_test(threads, thread_rtm_mix, "rtm-mix");