NEX-6859 TX-commit callback that is registered in sync-ctx causes system panic
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>
Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com>

*** 21,30 ****
--- 21,31 ----
  /*
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  /*
+  * Copyright 2016 Nexenta Systems, Inc.  All rights reserved.
   * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
   */
  
  #ifndef _SYS_TXG_H
  #define _SYS_TXG_H
*** 72,81 ****
--- 73,84 ----
  extern void txg_sync_stop(struct dsl_pool *dp);
  extern uint64_t txg_hold_open(struct dsl_pool *dp, txg_handle_t *txghp);
  extern void txg_rele_to_quiesce(txg_handle_t *txghp);
  extern void txg_rele_to_sync(txg_handle_t *txghp);
  extern void txg_register_callbacks(txg_handle_t *txghp, list_t *tx_callbacks);
+ extern void txg_register_callbacks_sync(struct dsl_pool *dp,
+     uint64_t txg, list_t *tx_callbacks);
  
  extern void txg_delay(struct dsl_pool *dp, uint64_t txg, hrtime_t delta,
      hrtime_t resolution);
  extern void txg_kick(struct dsl_pool *dp);