Bug #51648 DBUG_SYNC_POINT is not defined on all platforms and mtr cant pre-check that

DBUG_SYNC_POINT has at least one strong limitation that it's not defined
on all platforms. It has issues cooperating with @@debug.
All in all its functionality is superseded by DEBUG_SYNC facility and
there is no reason to maintain the old less flexible one.

Fixed with adding debug_sync_set_action() function as a facility to set up
a sync-action in the server sources code and re-writing existing simulations
(found 3) to use it.
Couple of tests have been reworked as well.

The patch offers a pattern for setting sync-points in replication threads
where the standard DEBUG_SYNC does not suffice to reach goals.





mysql-test/extra/rpl_tests/rpl_get_master_version_and_clock.test:
  rewriting the test from GET_LOCK()-based to DEBUG_SYNC-based;
  a pattern of usage DEBUG_SYNC for replication testing is provided.
mysql-test/suite/rpl/r/rpl_get_master_version_and_clock.result:
  results are changed.
mysql-test/suite/rpl/t/rpl_get_master_version_and_clock.test:
  rewriting the test from GET_LOCK()-based to DEBUG_SYNC-based;
  limiting the test to run only with MIXED binlog-format as the test last
  some 10 secs sensitively contributing to the total of tests run.
mysql-test/suite/rpl/t/rpl_show_slave_running.test:
  rewriting the test from GET_LOCK()-based to DEBUG_SYNC-based.
sql/debug_sync.cc:
  adding debug_sync_set_action() function as a facility to set up
  a sync-action in the server sources code.
sql/debug_sync.h:
  externalizing debug_sync_set_action().
sql/item_func.cc:
  purging sources from DBUG_SYNC_POINT.
sql/mysql_priv.h:
  purging sources from DBUG_SYNC_POINT.
sql/slave.cc:
  rewriting failure simulations to base on DEBUG_SYNC rather than GET_LOCK()-based DBUG_SYNC_POINT.
sql/sql_repl.cc:
  removing an orphan failure simulation line because no counterpart in tests existing.

1 files changed, 38 insertions, 0 deletions

diff --git a/sql/debug_sync.cc b/sql/debug_sync.cc
index 2580d526b52..23a649a89fa 100644
--- a/sql/debug_sync.cc
+++ b/sql/debug_sync.cc
@@ -1903,4 +1903,42 @@ void debug_sync(THD *thd, const char *sync_point_name, size_t name_len)
   DBUG_VOID_RETURN;
 }
 
+/**
+  Define debug sync action.
+
+  @param[in]        thd             thread handle
+  @param[in]        action_str      action string
+
+  @return           status
+    @retval         FALSE           ok
+    @retval         TRUE            error
+
+  @description
+    The function is similar to @c debug_sync_eval_action but is
+    to be called immediately from the server code rather than 
+    to be triggered by setting a value to DEBUG_SYNC system variable.
+
+  @note
+    The input string is copied prior to be fed to
+    @c debug_sync_eval_action to let the latter modify it.
+
+    Caution.
+    The function allocates in THD::mem_root and therefore
+    is not recommended to be deployed inside big loops.    
+*/
+
+bool debug_sync_set_action(THD *thd, const char *action_str, size_t len)
+{
+  bool                  rc;
+  char *value;
+  DBUG_ENTER("debug_sync_set_action");
+  DBUG_ASSERT(thd);
+  DBUG_ASSERT(action_str);
+  
+  value= strmake_root(thd->mem_root, action_str, len);
+  rc= debug_sync_eval_action(thd, value);
+  DBUG_RETURN(rc);
+}
+
+
 #endif /* defined(ENABLED_DEBUG_SYNC) */