5981 Deadlock in dmu_objset_find_dp

*** 1744,1754 ****
  dmu_objset_find_dp_cb(void *arg)
  {
          dmu_objset_find_ctx_t *dcp = arg;
          dsl_pool_t *dp = dcp->dc_dp;
  
!         dsl_pool_config_enter(dp, FTAG);
  
          dmu_objset_find_dp_impl(dcp);
  
          dsl_pool_config_exit(dp, FTAG);
  }
--- 1744,1766 ----
  dmu_objset_find_dp_cb(void *arg)
  {
          dmu_objset_find_ctx_t *dcp = arg;
          dsl_pool_t *dp = dcp->dc_dp;
  
!         /*
!          * We need to get a pool_config_lock here, as there are several
!          * asssert(pool_config_held) down the stack. Getting a lock via
!          * dsl_pool_config_enter is risky, as it might be stalled by a
!          * pending writer. This would deadlock, as the write lock can
!          * only be granted when our parent thread gives up the lock.
!          * The _prio interface gives us priority over a pending writer.
!          * On the other hand, we don't risk to stall any pending writers,
!          * as the parent thread already holds a config lock. We give up
!          * our lock before the parent does, so in effect we do not prolong
!          * the waiting time for the writer.
!          */
!         dsl_pool_config_enter_prio(dp, FTAG);
  
          dmu_objset_find_dp_impl(dcp);
  
          dsl_pool_config_exit(dp, FTAG);
  }