Add InnoDB UNIV_SYNC_DEBUG assertions to rw-lock code.

rw_lock_x_lock_func(): Assert that the thread is not already holding
the lock in a conflicting mode (RW_LOCK_SHARED).

rw_lock_s_lock_func(): Assert that the thread is not already holding
the lock in a conflicting mode (RW_LOCK_EX).

storage/innobase/include/sync0rw.ic

@@ -238,6 +238,7 @@ rw_lock_s_lock_func(
 
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(!rw_lock_own(lock, RW_LOCK_SHARED)); /* see NOTE above */
+	ut_ad(!rw_lock_own(lock, RW_LOCK_EX));
 #endif /* UNIV_SYNC_DEBUG */
 
 	mutex_enter(rw_lock_get_mutex(lock));

storage/innobase/sync/sync0rw.c

@@ -476,6 +476,9 @@ rw_lock_x_lock_func(
 	ulint	i;	/* spin round count */
 
 	ut_ad(rw_lock_validate(lock));
+#ifdef UNIV_SYNC_DEBUG
+	ut_ad(!rw_lock_own(lock, RW_LOCK_SHARED));
+#endif /* UNIV_SYNC_DEBUG */
 
 lock_loop:
 	/* Acquire the mutex protecting the rw-lock fields */

storage/innodb_plugin/include/sync0rw.ic

@@ -406,6 +406,7 @@ rw_lock_s_lock_func(
 
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(!rw_lock_own(lock, RW_LOCK_SHARED)); /* see NOTE above */
+	ut_ad(!rw_lock_own(lock, RW_LOCK_EX));
 #endif /* UNIV_SYNC_DEBUG */
 
 	/* TODO: study performance of UNIV_LIKELY branch prediction hints. */

storage/innodb_plugin/sync/sync0rw.c

@@ -612,6 +612,9 @@ rw_lock_x_lock_func(
 	ibool   spinning = FALSE;
 
 	ut_ad(rw_lock_validate(lock));
+#ifdef UNIV_SYNC_DEBUG
+	ut_ad(!rw_lock_own(lock, RW_LOCK_SHARED));
+#endif /* UNIV_SYNC_DEBUG */
 
 	i = 0;