WL#4259 - Debug Sync Facility

Backport from 6.0 to 5.1.
Only those sync points are included, which are used in debug_sync.test.

  The Debug Sync Facility allows to place synchronization points
  in the code:
  
  open_tables(...)
  
  DEBUG_SYNC(thd, "after_open_tables");
  
  lock_tables(...)
  
  When activated, a sync point can
  
  - Send a signal and/or
  - Wait for a signal
  
  Nomenclature:
  
  - signal:            A value of a global variable that persists
                       until overwritten by a new signal. The global
                       variable can also be seen as a "signal post"
                       or "flag mast". Then the signal is what is
                       attached to the "signal post" or "flag mast".
  
  - send a signal:     Assign the value (the signal) to the global
                       variable ("set a flag") and broadcast a
                       global condition to wake those waiting for
                       a signal.
  
  - wait for a signal: Loop over waiting for the global condition until
                       the global value matches the wait-for signal.
  
  Please find more information in the top comment in debug_sync.cc
  or in the worklog entry.


.bzrignore:
  WL#4259 - Debug Sync Facility
  Added the symbolic link libmysqld/debug_sync.cc.
CMakeLists.txt:
  WL#4259 - Debug Sync Facility
  Added definition for ENABLED_DEBUG_SYNC.
configure.in:
  WL#4259 - Debug Sync Facility
  Added definition for ENABLED_DEBUG_SYNC.
include/my_sys.h:
  WL#4259 - Debug Sync Facility
  Added definition for the DEBUG_SYNC_C macro.
libmysqld/CMakeLists.txt:
  WL#4259 - Debug Sync Facility
  Added sql/debug_sync.cc.
libmysqld/Makefile.am:
  WL#4259 - Debug Sync Facility
  Added sql/debug_sync.cc.
mysql-test/include/have_debug_sync.inc:
  WL#4259 - Debug Sync Facility
  New include file.
mysql-test/mysql-test-run.pl:
  WL#4259 - Debug Sync Facility
  Added option --debug_sync_timeout.
mysql-test/r/debug_sync.result:
  WL#4259 - Debug Sync Facility
  New test result.
mysql-test/r/have_debug_sync.require:
  WL#4259 - Debug Sync Facility
  New require file.
mysql-test/t/debug_sync.test:
  WL#4259 - Debug Sync Facility
  New test file.
mysys/my_static.c:
  WL#4259 - Debug Sync Facility
  Added definition for debug_sync_C_callback_ptr.
mysys/thr_lock.c:
  WL#4259 - Debug Sync Facility
  Added sync point "wait_for_lock".
sql/CMakeLists.txt:
  WL#4259 - Debug Sync Facility
  Added debug_sync.cc and debug_sync.h.
sql/Makefile.am:
  WL#4259 - Debug Sync Facility
  Added debug_sync.cc and debug_sync.h.
sql/debug_sync.cc:
  WL#4259 - Debug Sync Facility
  New source file.
sql/debug_sync.h:
  WL#4259 - Debug Sync Facility
  New header file.
sql/mysqld.cc:
  WL#4259 - Debug Sync Facility
  Added opt_debug_sync_timeout.
  Added calls to debug_sync_init() and debug_sync_end().
  Fixed a purecov comment (unrelated).
sql/set_var.cc:
  WL#4259 - Debug Sync Facility
  Added server variable "debug_sync".
sql/set_var.h:
  WL#4259 - Debug Sync Facility
  Added declaration for server variable "debug_sync".
sql/share/errmsg.txt:
  WL#4259 - Debug Sync Facility
  Added error messages ER_DEBUG_SYNC_TIMEOUT and ER_DEBUG_SYNC_HIT_LIMIT.
sql/sql_base.cc:
  WL#4259 - Debug Sync Facility
  Added sync points "after_flush_unlock" and "before_lock_tables_takes_lock".
sql/sql_class.cc:
  WL#4259 - Debug Sync Facility
  Added initialization for debug_sync_control to THD::THD.
  Added calls to debug_sync_init_thread() and debug_sync_end_thread().
sql/sql_class.h:
  WL#4259 - Debug Sync Facility
  Added element debug_sync_control to THD.
storage/myisam/myisamchk.c:
  Fixed a typo in an error message string (unrelated).

.bzrignore

@@ -3064,3 +3064,4 @@ sql/share/spanish
 sql/share/swedish
 sql/share/ukrainian
 libmysqld/examples/mysqltest.cc
+libmysqld/debug_sync.cc

CMakeLists.txt

@@ -66,6 +66,12 @@ IF(EXTRA_DEBUG)
   ADD_DEFINITIONS(-D EXTRA_DEBUG)
 ENDIF(EXTRA_DEBUG)
 
+IF(ENABLED_DEBUG_SYNC)
+  ADD_DEFINITIONS(-D ENABLED_DEBUG_SYNC)
+ENDIF(ENABLED_DEBUG_SYNC)
+SET(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DENABLED_DEBUG_SYNC")
+SET(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -DENABLED_DEBUG_SYNC")
+
 # in some places we use DBUG_OFF
 SET(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -DDBUG_OFF")
 SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -DDBUG_OFF")

configure.in

@@ -1708,6 +1708,23 @@ else
   CXXFLAGS="$OPTIMIZE_CXXFLAGS $CXXFLAGS"
 fi
 
+# Debug Sync Facility. NOTE: depends on 'with_debug'. Must be behind it.
+AC_MSG_CHECKING(if Debug Sync Facility should be enabled.)
+AC_ARG_ENABLE(debug_sync,
+              AS_HELP_STRING([--enable-debug-sync],
+                             [Build a version with Debug Sync Facility]),
+              [ enable_debug_sync=$enableval ],
+              [ enable_debug_sync=$with_debug ])
+
+if test "$enable_debug_sync" != "no"
+then
+  AC_DEFINE([ENABLED_DEBUG_SYNC], [1],
+            [If Debug Sync Facility should be enabled])
+  AC_MSG_RESULT([yes]) 
+else
+  AC_MSG_RESULT([no])
+fi
+
 # If we should allow error injection tests
 AC_ARG_WITH(error-inject,
     AC_HELP_STRING([--with-error-inject],[Enable error injection in MySQL Server]),

include/my_sys.h

@@ -172,6 +172,16 @@ extern char *my_strndup(const char *from, size_t length,
 #define TRASH(A,B) /* nothing */
 #endif
 
+#if defined(ENABLED_DEBUG_SYNC)
+extern void (*debug_sync_C_callback_ptr)(const char *, size_t);
+#define DEBUG_SYNC_C(_sync_point_name_) do {                            \
+    if (debug_sync_C_callback_ptr != NULL)                              \
+      (*debug_sync_C_callback_ptr)(STRING_WITH_LEN(_sync_point_name_)); } \
+  while(0)
+#else
+#define DEBUG_SYNC_C(_sync_point_name_)
+#endif /* defined(ENABLED_DEBUG_SYNC) */
+
 #ifdef HAVE_LARGE_PAGES
 extern uint my_get_large_page_size(void);
 extern uchar * my_large_malloc(size_t size, myf my_flags);

libmysqld/CMakeLists.txt

@@ -129,6 +129,7 @@ SET(LIBMYSQLD_SOURCES emb_qcache.cc libmysqld.c lib_sql.cc
            ../sql/sql_list.cc ../sql/sql_load.cc ../sql/sql_locale.cc 
            ../sql/sql_binlog.cc ../sql/sql_manager.cc ../sql/sql_map.cc 
            ../sql/sql_parse.cc ../sql/sql_partition.cc ../sql/sql_plugin.cc 
+           ../sql/debug_sync.cc
            ../sql/sql_prepare.cc ../sql/sql_rename.cc ../sql/sql_repl.cc 
            ../sql/sql_select.cc ../sql/sql_servers.cc
            ../sql/sql_show.cc ../sql/sql_state.c ../sql/sql_string.cc

libmysqld/Makefile.am

@@ -74,6 +74,7 @@ sqlsources = derror.cc field.cc field_conv.cc strfunc.cc filesort.cc \
 	sp_head.cc sp_pcontext.cc sp.cc sp_cache.cc sp_rcontext.cc \
 	parse_file.cc sql_view.cc sql_trigger.cc my_decimal.cc \
 	rpl_filter.cc sql_partition.cc sql_builtin.cc sql_plugin.cc \
+	debug_sync.cc \
 	sql_tablespace.cc \
 	rpl_injector.cc my_user.c partition_info.cc \
 	sql_servers.cc event_parse_data.cc

mysql-test/include/have_debug_sync.inc

+--require r/have_debug_sync.require
+disable_query_log;
+let $value= query_get_value(SHOW VARIABLES LIKE 'debug_sync', Value, 1);
+eval SELECT ('$value' LIKE 'ON %') AS debug_sync;
+enable_query_log;

mysql-test/mysql-test-run.pl

@@ -226,6 +226,7 @@ my @default_valgrind_args= ("--show-reachable=yes");
 my @valgrind_args;
 my $opt_valgrind_path;
 my $opt_callgrind;
+my $opt_debug_sync_timeout= 300; # Default timeout for WAIT_FOR actions.
 
 our $opt_warnings= 1;
 
@@ -867,6 +868,7 @@ sub command_line_setup {
              'valgrind-option=s'        => \@valgrind_args,
              'valgrind-path=s'          => \$opt_valgrind_path,
 	     'callgrind'                => \$opt_callgrind,
+	     'debug-sync-timeout=i'     => \$opt_debug_sync_timeout,
 
 	     # Directories
              'tmpdir=s'                 => \$opt_tmpdir,
@@ -4170,6 +4172,11 @@ sub mysqld_arguments ($$$) {
     mtr_add_arg($args, "%s", "--core-file");
   }
 
+  # Enable the debug sync facility, set default wait timeout.
+  # Facility stays disabled if timeout value is zero.
+  mtr_add_arg($args, "--loose-debug-sync-timeout=%s",
+              $opt_debug_sync_timeout);
+
   return $args;
 }
 
@@ -5280,6 +5287,8 @@ Misc options
                         to turn off.
 
   sleep=SECONDS         Passed to mysqltest, will be used as fixed sleep time
+  debug-sync-timeout=NUM Set default timeout for WAIT_FOR debug sync
+                        actions. Disable facility with NUM=0.
   gcov                  Collect coverage information after the test.
                         The result is a gcov file per source and header file.
   experimental=<file>   Refer to list of tests considered experimental;

mysql-test/r/have_debug_sync.require

+debug_sync
+1

mysys/my_static.c

@@ -92,6 +92,14 @@ int (*error_handler_hook)(uint error,const char *str,myf MyFlags)=
 int (*fatal_error_handler_hook)(uint error,const char *str,myf MyFlags)=
   my_message_no_curses;
 
+#if defined(ENABLED_DEBUG_SYNC)
+/**
+  Global pointer to be set if callback function is defined
+  (e.g. in mysqld). See sql/debug_sync.cc.
+*/
+void (*debug_sync_C_callback_ptr)(const char *, size_t);
+#endif /* defined(ENABLED_DEBUG_SYNC) */
+
 #ifdef __WIN__
 /* from my_getsystime.c */
 ulonglong query_performance_frequency, query_performance_offset;

mysys/thr_lock.c

@@ -398,6 +398,28 @@ wait_for_lock(struct st_lock_list *wait, THR_LOCK_DATA *data,
   my_bool can_deadlock= test(data->owner->info->n_cursors);
   DBUG_ENTER("wait_for_lock");
 
+  /*
+    One can use this to signal when a thread is going to wait for a lock.
+    See debug_sync.cc.
+
+    Beware of waiting for a signal here. The lock has aquired its mutex.
+    While waiting on a signal here, the locking thread could not aquire
+    the mutex to release the lock. One could lock up the table
+    completely.
+
+    In detail it works so: When thr_lock() tries to acquire a table
+    lock, it locks the lock->mutex, checks if it can have the lock, and
+    if not, it calls wait_for_lock(). Here it unlocks the table lock
+    while waiting on a condition. The sync point is located before this
+    wait for condition. If we have a waiting action here, we hold the
+    the table locks mutex all the time. Any attempt to look at the table
+    lock by another thread blocks it immediately on lock->mutex. This
+    can easily become an unexpected and unobvious blockage. So be
+    warned: Do not request a WAIT_FOR action for the 'wait_for_lock'
+    sync point unless you really know what you do.
+  */
+  DEBUG_SYNC_C("wait_for_lock");
+
   if (!in_wait_list)
   {
     (*wait->last)=data;				/* Wait for lock */

sql/CMakeLists.txt

@@ -64,6 +64,7 @@ SET (SQL_SOURCE
                sql_error.cc sql_handler.cc sql_help.cc sql_insert.cc sql_lex.cc 
                sql_list.cc sql_load.cc sql_manager.cc sql_map.cc sql_parse.cc 
                sql_partition.cc sql_plugin.cc sql_prepare.cc sql_rename.cc 
+               debug_sync.cc debug_sync.h
                sql_repl.cc sql_select.cc sql_show.cc sql_state.c sql_string.cc 
                sql_table.cc sql_test.cc sql_trigger.cc sql_udf.cc sql_union.cc
                sql_update.cc sql_view.cc strfunc.cc table.cc thr_malloc.cc 

sql/Makefile.am

@@ -58,6 +58,7 @@ noinst_HEADERS =	item.h item_func.h item_sum.h item_cmpfunc.h \
 			ha_ndbcluster.h ha_ndbcluster_cond.h \
 			ha_ndbcluster_binlog.h ha_ndbcluster_tables.h \
 			ha_partition.h rpl_constants.h \
+			debug_sync.h \
 			opt_range.h protocol.h rpl_tblmap.h rpl_utility.h \
 			rpl_reporting.h \
 			log.h sql_show.h rpl_rli.h rpl_mi.h \
@@ -102,6 +103,7 @@ mysqld_SOURCES =	sql_lex.cc sql_handler.cc sql_partition.cc \
 			discover.cc time.cc opt_range.cc opt_sum.cc \
 		   	records.cc filesort.cc handler.cc \
 		        ha_partition.cc \
+			debug_sync.cc \
 			sql_db.cc sql_table.cc sql_rename.cc sql_crypt.cc \
 			sql_load.cc mf_iocache.cc field_conv.cc sql_show.cc \
 			sql_udf.cc sql_analyse.cc sql_analyse.h sql_cache.cc \

sql/debug_sync.h

+#ifndef DEBUG_SYNC_INCLUDED
+#define DEBUG_SYNC_INCLUDED
+
+/* Copyright (C) 2008 Sun Microsystems, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
+
+/**
+  @file
+
+  Declarations for the Debug Sync Facility. See debug_sync.cc for details.
+*/
+
+#ifdef USE_PRAGMA_INTERFACE
+#pragma interface                      /* gcc class implementation */
+#endif
+
+#include <my_global.h>
+
+class THD;
+
+#if defined(ENABLED_DEBUG_SYNC)
+
+/* Macro to be put in the code at synchronization points. */
+#define DEBUG_SYNC(_thd_, _sync_point_name_)                            \
+          do { if (unlikely(opt_debug_sync_timeout))                    \
+               debug_sync(_thd_, STRING_WITH_LEN(_sync_point_name_));   \
+             } while (0)
+
+/* Command line option --debug-sync-timeout. See mysqld.cc. */
+extern uint opt_debug_sync_timeout;
+
+/* Default WAIT_FOR timeout if command line option is given without argument. */
+#define DEBUG_SYNC_DEFAULT_WAIT_TIMEOUT 300
+
+/* Debug Sync prototypes. See debug_sync.cc. */
+extern int  debug_sync_init(void);
+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);
+
+#else /* defined(ENABLED_DEBUG_SYNC) */
+
+#define DEBUG_SYNC(_thd_, _sync_point_name_)    /* disabled DEBUG_SYNC */
+
+#endif /* defined(ENABLED_DEBUG_SYNC) */
+
+#endif /* DEBUG_SYNC_INCLUDED */

sql/mysqld.cc

@@ -26,6 +26,7 @@
 #include "mysqld_suffix.h"
 #include "mysys_err.h"
 #include "events.h"
+#include "debug_sync.h"
 
 #include "../storage/myisam/ha_myisam.h"
 
@@ -486,6 +487,9 @@ my_bool lower_case_file_system= 0;
 my_bool opt_large_pages= 0;
 my_bool opt_myisam_use_mmap= 0;
 uint    opt_large_page_size= 0;
+#if defined(ENABLED_DEBUG_SYNC)
+uint    opt_debug_sync_timeout= 0;
+#endif /* defined(ENABLED_DEBUG_SYNC) */
 my_bool opt_old_style_user_limits= 0, trust_function_creators= 0;
 /*
   True if there is at least one per-hour limit for some user, so we should
@@ -1333,6 +1337,10 @@ void clean_up(bool print_message)
 #ifdef USE_REGEX
   my_regex_end();
 #endif
+#if defined(ENABLED_DEBUG_SYNC)
+  /* End the debug sync facility. See debug_sync.cc. */
+  debug_sync_end();
+#endif /* defined(ENABLED_DEBUG_SYNC) */
 
 #if !defined(EMBEDDED_LIBRARY)
   if (!opt_bootstrap)
@@ -3464,6 +3472,12 @@ static int init_common_variables(const char *conf_file_name, int argc,
   sys_var_slow_log_path.value= my_strdup(s, MYF(0));
   sys_var_slow_log_path.value_length= strlen(s);
 
+#if defined(ENABLED_DEBUG_SYNC)
+  /* Initialize the debug sync facility. See debug_sync.cc. */
+  if (debug_sync_init())
+    return 1; /* purecov: tested */
+#endif /* defined(ENABLED_DEBUG_SYNC) */
+
 #if (ENABLE_TEMP_POOL)
   if (use_temp_pool && bitmap_init(&temp_pool,0,1024,1))
     return 1;
@@ -4858,7 +4872,7 @@ void create_thread_to_handle_connection(THD *thd)
                               handle_one_connection,
                               (void*) thd)))
     {
-      /* purify: begin inspected */
+      /* purecov: begin inspected */
       DBUG_PRINT("error",
                  ("Can't create thread to handle request (error %d)",
                   error));
@@ -5671,6 +5685,9 @@ enum options_mysqld
   OPT_SECURE_FILE_PRIV,
   OPT_MIN_EXAMINED_ROW_LIMIT,
   OPT_LOG_SLOW_SLAVE_STATEMENTS,
+#if defined(ENABLED_DEBUG_SYNC)
+  OPT_DEBUG_SYNC_TIMEOUT,
+#endif /* defined(ENABLED_DEBUG_SYNC) */
   OPT_OLD_MODE,
   OPT_SLAVE_EXEC_MODE,
   OPT_GENERAL_LOG_FILE,
@@ -6442,6 +6459,14 @@ log and this option does nothing anymore.",
    "Decision to use in heuristic recover process. Possible values are COMMIT or ROLLBACK.",
    (uchar**) &opt_tc_heuristic_recover, (uchar**) &opt_tc_heuristic_recover,
    0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
+#if defined(ENABLED_DEBUG_SYNC)
+  {"debug-sync-timeout", OPT_DEBUG_SYNC_TIMEOUT,
+   "Enable the debug sync facility "
+   "and optionally specify a default wait timeout in seconds. "
+   "A zero value keeps the facility disabled.",
+   (uchar**) &opt_debug_sync_timeout, 0,
+   0, GET_UINT, OPT_ARG, 0, 0, UINT_MAX, 0, 0, 0},
+#endif /* defined(ENABLED_DEBUG_SYNC) */
   {"temp-pool", OPT_TEMP_POOL,
 #if (ENABLE_TEMP_POOL)
    "Using this option will cause most temporary files created to use a small set of names, rather than a unique name for each new file.",
@@ -7626,6 +7651,9 @@ static int mysql_init_variables(void)
   bzero((uchar*) &mysql_tmpdir_list, sizeof(mysql_tmpdir_list));
   bzero((char *) &global_status_var, sizeof(global_status_var));
   opt_large_pages= 0;
+#if defined(ENABLED_DEBUG_SYNC)
+  opt_debug_sync_timeout= 0;
+#endif /* defined(ENABLED_DEBUG_SYNC) */
   key_map_full.set_all();
 
   /* Character sets */
@@ -8360,6 +8388,22 @@ mysqld_get_one_option(int optid,
     lower_case_table_names= argument ? atoi(argument) : 1;
     lower_case_table_names_used= 1;
     break;
+#if defined(ENABLED_DEBUG_SYNC)
+  case OPT_DEBUG_SYNC_TIMEOUT:
+    /*
+      Debug Sync Facility. See debug_sync.cc.
+      Default timeout for WAIT_FOR action.
+      Default value is zero (facility disabled).
+      If option is given without an argument, supply a non-zero value.
+    */
+    if (!argument)
+    {
+      /* purecov: begin tested */
+      opt_debug_sync_timeout= DEBUG_SYNC_DEFAULT_WAIT_TIMEOUT;
+      /* purecov: end */
+    }
+    break;
+#endif /* defined(ENABLED_DEBUG_SYNC) */
   }
   return 0;
 }

sql/set_var.cc

@@ -625,6 +625,12 @@ static sys_var_long_ptr	sys_table_cache_size(&vars, "table_open_cache",
 					     &table_cache_size);
 static sys_var_long_ptr	sys_table_lock_wait_timeout(&vars, "table_lock_wait_timeout",
                                                     &table_lock_wait_timeout);
+
+#if defined(ENABLED_DEBUG_SYNC)
+/* Debug Sync Facility. Implemented in debug_sync.cc. */
+static sys_var_debug_sync sys_debug_sync(&vars, "debug_sync");
+#endif /* defined(ENABLED_DEBUG_SYNC) */
+
 static sys_var_long_ptr	sys_thread_cache_size(&vars, "thread_cache_size",
 					      &thread_cache_size);
 #if HAVE_POOL_OF_THREADS == 1

sql/set_var.h

@@ -637,6 +637,21 @@ public:
 };
 #endif /* DBUG_OFF */
 
+#if defined(ENABLED_DEBUG_SYNC)
+/* Debug Sync Facility. Implemented in debug_sync.cc. */
+class sys_var_debug_sync :public sys_var_thd
+{
+public:
+  sys_var_debug_sync(sys_var_chain *chain, const char *name_arg)
+    :sys_var_thd(name_arg)
+  { chain_sys_var(chain); }
+  bool check(THD *thd, set_var *var);
+  bool update(THD *thd, set_var *var);
+  SHOW_TYPE show_type() { return SHOW_CHAR; }
+  bool check_update_type(Item_result type) { return type != STRING_RESULT; }
+  uchar *value_ptr(THD *thd, enum_var_type type, LEX_STRING *base);
+};
+#endif /* defined(ENABLED_DEBUG_SYNC) */
 
 /* some variables that require special handling */
 

sql/share/errmsg.txt

@@ -6206,3 +6206,10 @@ ER_TOO_MANY_CONCURRENT_TRXS
 
 WARN_NON_ASCII_SEPARATOR_NOT_IMPLEMENTED
   eng "Non-ASCII separator arguments are not fully supported"
+
+ER_DEBUG_SYNC_TIMEOUT
+  eng "debug sync point wait timed out"
+  ger "Debug Sync Point Wartezeit berschritten"
+ER_DEBUG_SYNC_HIT_LIMIT
+  eng "debug sync point hit limit reached"
+  ger "Debug Sync Point Hit Limit erreicht"

sql/sql_base.cc

@@ -17,6 +17,7 @@
 /* Basic functions needed by many modules */
 
 #include "mysql_priv.h"
+#include "debug_sync.h"
 #include "sql_select.h"
 #include "sp_head.h"
 #include "sp.h"
@@ -950,6 +951,7 @@ bool close_cached_tables(THD *thd, TABLE_LIST *tables, bool have_lock,
 
     close_old_data_files(thd,thd->open_tables,1,1);
     mysql_ha_flush(thd);
+    DEBUG_SYNC(thd, "after_flush_unlock");
 
     bool found=1;
     /* Wait until all threads has closed all the tables we had locked */
@@ -5289,6 +5291,8 @@ int lock_tables(THD *thd, TABLE_LIST *tables, uint count, bool *need_reopen)
       }
     }
 
+    DEBUG_SYNC(thd, "before_lock_tables_takes_lock");
+
     if (! (thd->lock= mysql_lock_tables(thd, start, (uint) (ptr - start),
                                         lock_flag, need_reopen)))
     {

sql/sql_class.cc

@@ -42,6 +42,7 @@
 
 #include "sp_rcontext.h"
 #include "sp_cache.h"
+#include "debug_sync.h"
 
 /*
   The following is used to initialise Table_ident with a internal
@@ -584,6 +585,9 @@ THD::THD()
    derived_tables_processing(FALSE),
    spcont(NULL),
    m_parser_state(NULL)
+#if defined(ENABLED_DEBUG_SYNC)
+   , debug_sync_control(0)
+#endif /* defined(ENABLED_DEBUG_SYNC) */
 {
   ulong tmp;
 
@@ -832,6 +836,11 @@ void THD::init(void)
   reset_current_stmt_binlog_row_based();
   bzero((char *) &status_var, sizeof(status_var));
   sql_log_bin_toplevel= options & OPTION_BIN_LOG;
+
+#if defined(ENABLED_DEBUG_SYNC)
+  /* Initialize the Debug Sync Facility. See debug_sync.cc. */
+  debug_sync_init_thread(this);
+#endif /* defined(ENABLED_DEBUG_SYNC) */
 }
 
 
@@ -911,6 +920,12 @@ void THD::cleanup(void)
     lock=locked_tables; locked_tables=0;
     close_thread_tables(this);
   }
+
+#if defined(ENABLED_DEBUG_SYNC)
+  /* End the Debug Sync Facility. See debug_sync.cc. */
+  debug_sync_end_thread(this);
+#endif /* defined(ENABLED_DEBUG_SYNC) */
+
   mysql_ha_cleanup(this);
   delete_dynamic(&user_var_events);
   hash_free(&user_vars);

sql/sql_class.h

@@ -1896,6 +1896,11 @@ public:
   partition_info *work_part_info;
 #endif
 
+#if defined(ENABLED_DEBUG_SYNC)
+  /* Debug Sync facility. See debug_sync.cc. */
+  struct st_debug_sync_control *debug_sync_control;
+#endif /* defined(ENABLED_DEBUG_SYNC) */
+
   THD();
   ~THD();
 

storage/myisam/myisamchk.c

@@ -837,7 +837,7 @@ static int myisamchk(MI_CHECK *param, char * filename)
       mi_check_print_error(param,"'%s' is marked as crashed after last repair",filename);
       break;
     case HA_ERR_OLD_FILE:
-      mi_check_print_error(param,"'%s' is a old type of MyISAM-table", filename);
+      mi_check_print_error(param,"'%s' is an old type of MyISAM-table", filename);
       break;
     case HA_ERR_END_OF_FILE:
       mi_check_print_error(param,"Couldn't read complete header from '%s'", filename);