Ticket #48146 - async simple paged results issue; need to close a small window for a pr index competed among multiple threads.

Description: If multiple async simple paged results requests come in via one
connection simultaneously, the same slot in the paged results array in the
connection could be shared.  If one of them has to do paging, the search
request object stashed in the paged result array slot could be freed by the
other request if it has the shorter life cycle.

These 3 reqs use the same paged results array slot.
req0: <--------------><----x
page1           page2
req1: <----->
req2:              <------->
frees search result object of req0

Reviewed by [email protected] (Thank you, Rich!!)

(cherry picked from commit 3cf85d1ad6cbc0feac5578dee5ce259c0f65055f)

ldap/servers/slapd/opshared.c

@@ -408,6 +408,51 @@ op_shared_search (Slapi_PBlock *pb, int send_result)
    */
   operation_set_target_spec (pb->pb_op, basesdn);
 
+  if (be_name == NULL)
+  {
+    /* no specific backend was requested, use the mapping tree
+     */
+    err_code = slapi_mapping_tree_select_all(pb, be_list, referral_list, errorbuf);
+    if (((err_code != LDAP_SUCCESS) && (err_code != LDAP_OPERATIONS_ERROR) && (err_code != LDAP_REFERRAL))
+      || ((err_code == LDAP_OPERATIONS_ERROR) && (be_list[0] == NULL)))
+    {
+      send_ldap_result(pb, err_code, NULL, errorbuf, 0, NULL);
+      rc = -1;
+      goto free_and_return;
+    }
+    if (be_list[0] != NULL)
+    {
+      index = 0;
+      if (pr_be) { /* PAGED RESULT: be is found from the previous paging. */
+        /* move the index in the be_list which matches pr_be */
+        while (be_list[index] && be_list[index+1] && pr_be != be_list[index])
+          index++;
+      } else {
+        while (be_list[index] && be_list[index+1])
+          index++;
+      }
+      /* "be" is either pr_be or the last backend */
+      be = be_list[index];
+    }
+    else
+      be = pr_be?pr_be:NULL;
+  }
+  else
+  {
+      /* specific backend be_name was requested, use slapi_be_select_by_instance_name
+       */
+      if (pr_be) {
+        be_single = be = pr_be;
+      } else {
+        be_single = be = slapi_be_select_by_instance_name(be_name);
+      }
+      if (be_single)
+        slapi_be_Rlock(be_single);
+      be_list[0] = NULL;
+      referral_list[0] = NULL;
+      referral = NULL;
+  }
+
   /* this is time to check if mapping tree specific control
    * was used to specify that we want to parse only 
    * one backend 
@@ -478,8 +523,7 @@ op_shared_search (Slapi_PBlock *pb, int send_result)
       if ( slapi_control_present (ctrlp, LDAP_CONTROL_PAGEDRESULTS,
                                   &ctl_value, &iscritical) )
       {
-          rc = pagedresults_parse_control_value(pb, ctl_value,
-                                                &pagesize, &pr_idx);
+          rc = pagedresults_parse_control_value(pb, ctl_value, &pagesize, &pr_idx, be);
           /* Let's set pr_idx even if it fails; in case, pr_idx == -1. */
           slapi_pblock_set(pb, SLAPI_PAGED_RESULTS_INDEX, &pr_idx);
           if ((LDAP_SUCCESS == rc) ||
@@ -520,51 +564,6 @@ op_shared_search (Slapi_PBlock *pb, int send_result)
       }
   }
 
-  if (be_name == NULL)
-  {
-    /* no specific backend was requested, use the mapping tree
-     */
-    err_code = slapi_mapping_tree_select_all(pb, be_list, referral_list, errorbuf);
-    if (((err_code != LDAP_SUCCESS) && (err_code != LDAP_OPERATIONS_ERROR) && (err_code != LDAP_REFERRAL))
-      || ((err_code == LDAP_OPERATIONS_ERROR) && (be_list[0] == NULL)))
-    {
-      send_ldap_result(pb, err_code, NULL, errorbuf, 0, NULL);
-      rc = -1;
-      goto free_and_return;
-    }
-    if (be_list[0] != NULL)
-    {
-      index = 0;
-      if (pr_be) { /* PAGED RESULT: be is found from the previous paging. */
-        /* move the index in the be_list which matches pr_be */
-        while (be_list[index] && be_list[index+1] && pr_be != be_list[index])
-          index++;
-      } else {
-        while (be_list[index] && be_list[index+1])
-          index++;
-      }
-      /* "be" is either pr_be or the last backend */
-      be = be_list[index];
-    }
-    else
-      be = pr_be?pr_be:NULL;
-  }
-  else
-  {
-      /* specific backend be_name was requested, use slapi_be_select_by_instance_name
-       */
-      if (pr_be) {
-        be_single = be = pr_be;
-      } else {
-        be_single = be = slapi_be_select_by_instance_name(be_name);
-      }
-      if (be_single)
-        slapi_be_Rlock(be_single);
-      be_list[0] = NULL;
-      referral_list[0] = NULL;
-      referral = NULL;
-  }
-
   slapi_pblock_set(pb, SLAPI_BACKEND_COUNT, &index);
 
   if (be)

ldap/servers/slapd/pagedresults.c

@@ -58,7 +58,7 @@
 int
 pagedresults_parse_control_value( Slapi_PBlock *pb,
                                   struct berval *psbvp, ber_int_t *pagesize,
-                                  int *index )
+                                  int *index, Slapi_Backend *be )
 {
     int rc = LDAP_SUCCESS;
     struct berval cookie = {0};
@@ -119,6 +119,7 @@ pagedresults_parse_control_value( Slapi_PBlock *pb,
         } else {
             for (i = 0; i < conn->c_pagedresults.prl_maxlen; i++) {
                 if (!conn->c_pagedresults.prl_list[i].pr_current_be) {
+                    conn->c_pagedresults.prl_list[i].pr_current_be = be;
                     *index = i;
                     break;
                 }

ldap/servers/slapd/proto-slap.h

@@ -1487,7 +1487,7 @@ int slapd_do_all_nss_ssl_init(int slapd_exemode, int importexport_encrypt,
  * pagedresults.c
  */
 int pagedresults_parse_control_value(Slapi_PBlock *pb, struct berval *psbvp,
-                                     ber_int_t *pagesize, int *index);
+                                     ber_int_t *pagesize, int *index, Slapi_Backend *be);
 void pagedresults_set_response_control(Slapi_PBlock *pb, int iscritical, 
                                        ber_int_t estimate,
                                        int curr_search_count, int index);