3746 ZRLs are racy
Submitted by:   Justin Gibbs <justing@spectralogic.com>

*** 74,83 ****
--- 74,84 ----
  zrl_add(zrlock_t *zrl)
  #endif
  {
          uint32_t n = (uint32_t)zrl->zr_refcount;
  
+         while (1) {
                  while (n != ZRL_LOCKED) {
                          uint32_t cas = atomic_cas_32(
                              (uint32_t *)&zrl->zr_refcount, n, n + 1);
                          if (cas == n) {
                                  ASSERT((int32_t)n >= 0);
*** 91,112 ****
  #endif
                          return;
                  }
                  n = cas;
          }
- 
          mutex_enter(&zrl->zr_mtx);
          while (zrl->zr_refcount == ZRL_LOCKED) {
                  cv_wait(&zrl->zr_cv, &zrl->zr_mtx);
          }
-         ASSERT(zrl->zr_refcount >= 0);
-         zrl->zr_refcount++;
- #ifdef  ZFS_DEBUG
-         zrl->zr_owner = curthread;
-         zrl->zr_caller = zc;
- #endif
          mutex_exit(&zrl->zr_mtx);
  }
  
  void
  zrl_remove(zrlock_t *zrl)
  {
--- 92,107 ----
  #endif
                                  return;
                          }
                          n = cas;
                  }
                  mutex_enter(&zrl->zr_mtx);
                  while (zrl->zr_refcount == ZRL_LOCKED) {
                          cv_wait(&zrl->zr_cv, &zrl->zr_mtx);
                  }
                  mutex_exit(&zrl->zr_mtx);
+         }
  }
  
  void
  zrl_remove(zrlock_t *zrl)
  {