Fix race in rwlock implementation which can occur when

your task is rescheduled to a different cpu after you've
taken the lock but before calling RW_LOCK_HELD is called.
We need the spinlock to ensure there is a wmb() there.


git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@68 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c

include/sys/rwlock.h

@@ -163,6 +163,8 @@ rw_tryenter(krwlock_t *rwlp, krw_t rw)
 				rwlp->rw_owner = current;
 			}
 			break;
+		default:
+			BUG_ON(1);
 	}
 
 	return result;
@@ -193,6 +195,8 @@ rw_enter(krwlock_t *rwlp, krw_t rw)
 			BUG_ON(rwlp->rw_owner != NULL);
 			rwlp->rw_owner = current;
 			break;
+		default:
+			BUG_ON(1);
 	}
 }