A follow-up to fix for

BUG#47073 - valgrind errs, corruption,failed repair of partition,
            low myisam_sort_buffer_size

Fixed race conditions discovered with the provided test case and
stabilized test case.

include/myisam.h:
  Serialize submission of messages from multi-threaded REPAIR.
mysql-test/r/myisam.result:
  REPAIR output highly depend on threads activity. Disabled
  result log to make test case deterministic.
mysql-test/t/myisam.test:
  REPAIR output highly depend on threads activity. Disabled
  result log to make test case deterministic.
storage/myisam/ha_myisam.cc:
  Serialize submission of messages from multi-threaded REPAIR.
storage/myisam/mi_check.c:
  Serialize submission of messages from multi-threaded REPAIR.
storage/myisam/sort.c:
  Only master thread is allowed to detach write cache from
  the share.

include/myisam.h

@@ -432,6 +432,10 @@ typedef struct st_mi_check_param
   const char *db_name, *table_name;
   const char *op_name;
   enum_mi_stats_method stats_method;
+#ifdef THREAD
+  pthread_mutex_t print_msg_mutex;
+  my_bool need_print_msg_lock;
+#endif
 } MI_CHECK;
 
 typedef struct st_sort_ft_buf

mysql-test/r/myisam.result

@@ -2290,6 +2290,12 @@ Table	Op	Msg_type	Msg_text
 test.t1	repair	error	myisam_sort_buffer_size is too small
 test.t1	repair	warning	Number of rows changed from 0 to 7168
 test.t1	repair	status	OK
+SET myisam_repair_threads=2;
+REPAIR TABLE t1;
+SET myisam_repair_threads=@@global.myisam_repair_threads;
 SET myisam_sort_buffer_size=@@global.myisam_sort_buffer_size;
+CHECK TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
 DROP TABLE t1;
 End of 5.1 tests

mysql-test/t/myisam.test

@@ -1539,14 +1539,14 @@ INSERT INTO t1 SELECT a+5120,b FROM t1;
 SET myisam_sort_buffer_size=4;
 REPAIR TABLE t1;
 
-# !!! Disabled until additional fix for BUG#47073 is pushed.
-#SET myisam_repair_threads=2;
+SET myisam_repair_threads=2;
 # May report different values depending on threads activity.
-#--replace_regex /changed from [0-9]+/changed from #/
-#REPAIR TABLE t1;
-#SET myisam_repair_threads=@@global.myisam_repair_threads;
-
+--disable_result_log
+REPAIR TABLE t1;
+--enable_result_log
+SET myisam_repair_threads=@@global.myisam_repair_threads;
 SET myisam_sort_buffer_size=@@global.myisam_sort_buffer_size;
+CHECK TABLE t1;
 DROP TABLE t1;
 
 --echo End of 5.1 tests

storage/myisam/ha_myisam.cc

@@ -115,6 +115,10 @@ static void mi_check_print_msg(MI_CHECK *param,	const char* msg_type,
     Also we likely need to lock mutex here (in both cases with protocol and
     push_warning).
   */
+#ifdef THREAD
+  if (param->need_print_msg_lock)
+    pthread_mutex_lock(&param->print_msg_mutex);
+#endif
   protocol->prepare_for_resend();
   protocol->store(name, length, system_charset_info);
   protocol->store(param->op_name, system_charset_info);
@@ -123,6 +127,10 @@ static void mi_check_print_msg(MI_CHECK *param,	const char* msg_type,
   if (protocol->write())
     sql_print_error("Failed on my_net_write, writing to stderr instead: %s\n",
 		    msgbuf);
+#ifdef THREAD
+  if (param->need_print_msg_lock)
+    pthread_mutex_unlock(&param->print_msg_mutex);
+#endif
   return;
 }
 

storage/myisam/mi_check.c

@@ -104,6 +104,9 @@ void myisamchk_init(MI_CHECK *param)
   param->max_record_length= LONGLONG_MAX;
   param->key_cache_block_size= KEY_CACHE_BLOCK_SIZE;
   param->stats_method= MI_STATS_METHOD_NULLS_NOT_EQUAL;
+#ifdef THREAD
+  param->need_print_msg_lock= 0;
+#endif
 }
 
 	/* Check the status flags for the table */
@@ -2703,6 +2706,8 @@ int mi_repair_parallel(MI_CHECK *param, register MI_INFO *info,
   /* Initialize pthread structures before goto err. */
   pthread_mutex_init(&sort_info.mutex, MY_MUTEX_INIT_FAST);
   pthread_cond_init(&sort_info.cond, 0);
+  pthread_mutex_init(&param->print_msg_mutex, MY_MUTEX_INIT_FAST);
+  param->need_print_msg_lock= 1;
 
   if (!(sort_info.key_block=
 	alloc_key_blocks(param, (uint) param->sort_key_blocks,
@@ -3108,6 +3113,8 @@ int mi_repair_parallel(MI_CHECK *param, register MI_INFO *info,
 
   pthread_cond_destroy (&sort_info.cond);
   pthread_mutex_destroy(&sort_info.mutex);
+  pthread_mutex_destroy(&param->print_msg_mutex);
+  param->need_print_msg_lock= 0;
 
   my_free((uchar*) sort_info.ft_buf, MYF(MY_ALLOW_ZERO_PTR));
   my_free((uchar*) sort_info.key_block,MYF(MY_ALLOW_ZERO_PTR));

storage/myisam/sort.c

@@ -466,8 +466,12 @@ pthread_handler_t thr_find_all_keys(void *arg)
       Detach from the share if the writer is involved. Avoid others to
       be blocked. This includes a flush of the write buffer. This will
       also indicate EOF to the readers.
+      That means that a writer always gets here first and readers -
+      only when they see EOF. But if a reader finishes prematurely
+      because of an error it may reach this earlier - don't allow it
+      to detach the writer thread.
     */
-    if (sort_param->sort_info->info->rec_cache.share)
+    if (sort_param->master && sort_param->sort_info->info->rec_cache.share)
       remove_io_thread(&sort_param->sort_info->info->rec_cache);
 
     /* Readers detach from the share if any. Avoid others to be blocked. */
@@ -789,6 +793,7 @@ static int NEAR_F merge_many_buff(MI_SORT_PARAM *info, uint keys,
   close_cached_file(to_file);                   /* This holds old result */
   if (to_file == t_file)
   {
+    DBUG_ASSERT(t_file2.type == WRITE_CACHE);
     *t_file=t_file2;                            /* Copy result file */
     t_file->current_pos= &t_file->write_pos;
     t_file->current_end= &t_file->write_end;