NEX-9755 Race in libshare can cause zfs set sharenfs to fail
Reviewed by: Rick McNeal <rick.mcneal@nexenta.com>
Reviewed by: Gordon Ross <gordon.ross@nexenta.com>

*** 51,62 ****
--- 51,66 ----
  
  struct sa_proto_plugin *sap_proto_list;
  
  static struct sa_proto_handle sa_proto_handle;
  
+ extern mutex_t sa_global_lock;
+ 
  void proto_plugin_fini();
  
+ static void proto_plugin_fini_impl(boolean_t);
+ 
  /*
   * Returns true if name is "." or "..", otherwise returns false.
   */
  static boolean_t
  proto_is_dot_or_dotdot(const char *name)
*** 93,108 ****
--- 97,118 ----
          struct dirent *dent;
          int ret = SA_OK;
          struct stat st;
          char isa[MAXISALEN];
  
+         assert(MUTEX_HELD(&sa_global_lock));
+ 
  #if defined(_LP64)
          if (sysinfo(SI_ARCHITECTURE_64, isa, MAXISALEN) == -1)
                  isa[0] = '\0';
  #else
          isa[0] = '\0';
  #endif
+         if (sap_proto_list != NULL && sa_proto_handle.sa_proto != NULL) {
+                 sa_proto_handle.sa_ref_count++;
+                 return (SA_OK);
+         }
  
          if ((dir = opendir(SA_LIB_DIR)) == NULL)
                  return (SA_OK);
  
          while ((dent = readdir(dir)) != NULL) {
*** 153,163 ****
                  sap_proto_list = proto;
          }
  
          (void) closedir(dir);
  
!         if (num_protos != 0) {
                  sa_proto_handle.sa_proto =
                      (char **)calloc(num_protos, sizeof (char *));
                  sa_proto_handle.sa_ops =
                      (struct sa_plugin_ops **)calloc(num_protos,
                      sizeof (struct sa_plugin_ops *));
--- 163,173 ----
                  sap_proto_list = proto;
          }
  
          (void) closedir(dir);
  
!         if (num_protos != 0 && sa_proto_handle.sa_proto == NULL) {
                  sa_proto_handle.sa_proto =
                      (char **)calloc(num_protos, sizeof (char *));
                  sa_proto_handle.sa_ops =
                      (struct sa_plugin_ops **)calloc(num_protos,
                      sizeof (struct sa_plugin_ops *));
*** 192,203 ****
          }
  
          /*
           * There was an error, so cleanup prior to return of failure.
           */
!         if (ret != SA_OK)
!                 proto_plugin_fini();
  
          return (ret);
  }
  
  /*
--- 202,217 ----
          }
  
          /*
           * There was an error, so cleanup prior to return of failure.
           */
!         if (ret != SA_OK) {
!                 proto_plugin_fini_impl(B_TRUE);
!         } else {
!                 assert(sa_proto_handle.sa_ref_count >= 0);
!                 sa_proto_handle.sa_ref_count++;
!         }
  
          return (ret);
  }
  
  /*
*** 207,219 ****
--- 221,255 ----
   */
  
  void
  proto_plugin_fini()
  {
+         assert(MUTEX_HELD(&sa_global_lock));
+ 
+         proto_plugin_fini_impl(B_FALSE);
+ }
+ 
+ static void
+ proto_plugin_fini_impl(boolean_t forcefini)
+ {
          struct sa_proto_plugin *p;
  
+         assert(MUTEX_HELD(&sa_global_lock));
+ 
+         sa_proto_handle.sa_ref_count--;
          /*
+          * If another thread has a reference to the proto list,
+          * we don't want to clear it out while they're using it
+          * or find_protocol() could fail.
+          */
+         if (!forcefini && sa_proto_handle.sa_ref_count > 0) {
+                 return;
+         } else {
+                 sa_proto_handle.sa_ref_count = 0;
+         }
+ 
+         /*
           * Protocols may call this framework during _fini
           * (the smbfs plugin is known to do this) so do
           * two passes: 1st call _fini; 2nd free, dlclose.
           */
          for (p = sap_proto_list; p != NULL; p = p->plugin_next)
*** 224,233 ****
--- 260,271 ----
  
                  if (p->plugin_handle != NULL)
                          (void) dlclose(p->plugin_handle);
                  free(p);
          }
+         if (sap_proto_list != NULL)
+                 sap_proto_list = NULL;
          if (sa_proto_handle.sa_ops != NULL) {
                  free(sa_proto_handle.sa_ops);
                  sa_proto_handle.sa_ops = NULL;
          }
          if (sa_proto_handle.sa_proto != NULL) {
*** 247,257 ****
  static struct sa_plugin_ops *
  find_protocol(char *proto)
  {
          int i;
          struct sa_plugin_ops *ops = NULL;
-         extern mutex_t sa_global_lock;
  
          (void) mutex_lock(&sa_global_lock);
          if (proto != NULL) {
                  for (i = 0; i < sa_proto_handle.sa_num_proto; i++) {
                          if (strcmp(proto, sa_proto_handle.sa_proto[i]) == 0) {
--- 285,294 ----