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All in all its functionality is superseded by DEBUG_SYNC facility and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.

6 files changed, 69 insertions, 92 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) */
diff --git a/sql/debug_sync.h b/sql/debug_sync.h
index f4cd0b364cf..9ac7da39d4d 100644
--- a/sql/debug_sync.h
+++ b/sql/debug_sync.h
@@ -50,6 +50,7 @@ extern void debug_sync_end(void);
 extern void debug_sync_init_thread(THD *thd);
 extern void debug_sync_end_thread(THD *thd);
 extern void debug_sync(THD *thd, const char *sync_point_name, size_t name_len);
+extern bool debug_sync_set_action(THD *thd, const char *action_str, size_t len);
 
 #else /* defined(ENABLED_DEBUG_SYNC) */
 
diff --git a/sql/item_func.cc b/sql/item_func.cc
index 845654c1881..1e31755179b 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -3362,80 +3362,6 @@ longlong Item_master_pos_wait::val_int()
   return event_count;
 }
 
-#ifdef EXTRA_DEBUG
-void debug_sync_point(const char* lock_name, uint lock_timeout)
-{
-  THD* thd=current_thd;
-  User_level_lock* ull;
-  struct timespec abstime;
-  size_t lock_name_len;
-  lock_name_len= strlen(lock_name);
-  pthread_mutex_lock(&LOCK_user_locks);
-
-  if (thd->ull)
-  {
-    item_user_lock_release(thd->ull);
-    thd->ull=0;
-  }
-
-  /*
-    If the lock has not been aquired by some client, we do not want to
-    create an entry for it, since we immediately release the lock. In
-    this case, we will not be waiting, but rather, just waste CPU and
-    memory on the whole deal
-  */
-  if (!(ull= ((User_level_lock*) hash_search(&hash_user_locks,
-                                             (uchar*) lock_name,
-                                             lock_name_len))))
-  {
-    pthread_mutex_unlock(&LOCK_user_locks);
-    return;
-  }
-  ull->count++;
-
-  /*
-    Structure is now initialized.  Try to get the lock.
-    Set up control struct to allow others to abort locks
-  */
-  thd_proc_info(thd, "User lock");
-  thd->mysys_var->current_mutex= &LOCK_user_locks;
-  thd->mysys_var->current_cond=  &ull->cond;
-
-  set_timespec(abstime,lock_timeout);
-  while (ull->locked && !thd->killed)
-  {
-    int error= pthread_cond_timedwait(&ull->cond, &LOCK_user_locks, &abstime);
-    if (error == ETIMEDOUT || error == ETIME)
-      break;
-  }
-
-  if (ull->locked)
-  {
-    if (!--ull->count)
-      delete ull;				// Should never happen
-  }
-  else
-  {
-    ull->locked=1;
-    ull->set_thread(thd);
-    thd->ull=ull;
-  }
-  pthread_mutex_unlock(&LOCK_user_locks);
-  pthread_mutex_lock(&thd->mysys_var->mutex);
-  thd_proc_info(thd, 0);
-  thd->mysys_var->current_mutex= 0;
-  thd->mysys_var->current_cond=  0;
-  pthread_mutex_unlock(&thd->mysys_var->mutex);
-  pthread_mutex_lock(&LOCK_user_locks);
-  if (thd->ull)
-  {
-    item_user_lock_release(thd->ull);
-    thd->ull=0;
-  }
-  pthread_mutex_unlock(&LOCK_user_locks);
-}
-
-#endif
 
 /**
   Get a user level lock.  If the thread has an old lock this is first released.
diff --git a/sql/mysql_priv.h b/sql/mysql_priv.h
index 90b02f5337a..098ea514cb6 100644
--- a/sql/mysql_priv.h
+++ b/sql/mysql_priv.h
@@ -580,20 +580,6 @@ protected:
 
 /* Used to check GROUP BY list in the MODE_ONLY_FULL_GROUP_BY mode */
 #define UNDEF_POS (-1)
-#ifdef EXTRA_DEBUG
-/**
-  Sync points allow us to force the server to reach a certain line of code
-  and block there until the client tells the server it is ok to go on.
-  The client tells the server to block with SELECT GET_LOCK()
-  and unblocks it with SELECT RELEASE_LOCK(). Used for debugging difficult
-  concurrency problems
-*/
-#define DBUG_SYNC_POINT(lock_name,lock_timeout) \
- debug_sync_point(lock_name,lock_timeout)
-void debug_sync_point(const char* lock_name, uint lock_timeout);
-#else
-#define DBUG_SYNC_POINT(lock_name,lock_timeout)
-#endif /* EXTRA_DEBUG */
 
 /* BINLOG_DUMP options */
 
diff --git a/sql/slave.cc b/sql/slave.cc
index a89ac2e682b..e8405ffcd37 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -44,6 +44,7 @@
 #ifdef HAVE_REPLICATION
 
 #include "rpl_tblmap.h"
+#include "debug_sync.h"
 
 #define FLAGSTR(V,F) ((V)&(F)?#F" ":"")
 
@@ -981,7 +982,16 @@ static int get_master_version_and_clock(MYSQL* mysql, Master_info* mi)
     unavailable (very old master not supporting UNIX_TIMESTAMP()?).
   */
 
-  DBUG_SYNC_POINT("debug_lock.before_get_UNIX_TIMESTAMP", 10);
+  DBUG_EXECUTE_IF("dbug.before_get_UNIX_TIMESTAMP",
+                  {
+                    const char act[]=
+                      "now "
+                      "wait_for signal.get_unix_timestamp";
+                    DBUG_ASSERT(opt_debug_sync_timeout > 0);
+                    DBUG_ASSERT(!debug_sync_set_action(current_thd,
+                                                       STRING_WITH_LEN(act)));
+                  };);
+
   master_res= NULL;
   if (!mysql_real_query(mysql, STRING_WITH_LEN("SELECT UNIX_TIMESTAMP()")) &&
       (master_res= mysql_store_result(mysql)) &&
@@ -1020,7 +1030,15 @@ static int get_master_version_and_clock(MYSQL* mysql, Master_info* mi)
     Note: we could have put a @@SERVER_ID in the previous SELECT
     UNIX_TIMESTAMP() instead, but this would not have worked on 3.23 masters.
   */
-  DBUG_SYNC_POINT("debug_lock.before_get_SERVER_ID", 10);
+  DBUG_EXECUTE_IF("dbug.before_get_SERVER_ID",
+                  {
+                    const char act[]=
+                      "now "
+                      "wait_for signal.get_server_id";
+                    DBUG_ASSERT(opt_debug_sync_timeout > 0);
+                    DBUG_ASSERT(!debug_sync_set_action(current_thd, 
+                                                       STRING_WITH_LEN(act)));
+                  };);
   master_res= NULL;
   master_row= NULL;
   if (!mysql_real_query(mysql,
@@ -2557,7 +2575,16 @@ pthread_handler_t handle_slave_io(void *arg)
 
 connected:
 
-  DBUG_SYNC_POINT("debug_lock.before_get_running_status_yes", 10);
+    DBUG_EXECUTE_IF("dbug.before_get_running_status_yes",
+                    {
+                      const char act[]=
+                        "now "
+                        "wait_for signal.io_thread_let_running";
+                      DBUG_ASSERT(opt_debug_sync_timeout > 0);
+                      DBUG_ASSERT(!debug_sync_set_action(thd, 
+                                                         STRING_WITH_LEN(act)));
+                    };);
+
   // TODO: the assignment below should be under mutex (5.0)
   mi->slave_running= MYSQL_SLAVE_RUN_CONNECT;
   thd->slave_net = &mysql->net;
diff --git a/sql/sql_repl.cc b/sql/sql_repl.cc
index ae995ea5ed3..44215d90634 100644
--- a/sql/sql_repl.cc
+++ b/sql/sql_repl.cc
@@ -1711,7 +1711,6 @@ int log_loaded_block(IO_CACHE* file)
       if (mysql_bin_log.write(&b))
         DBUG_RETURN(1);
       lf_info->wrote_create_file= 1;
-      DBUG_SYNC_POINT("debug_lock.created_file_event",10);
     }
   }
   DBUG_RETURN(0);