BUG#50364: FLUSH LOGS crashes the server (rpl.rpl_heartbeat_basic

fails in PB sporadically)
      
The IO thread can concurrently access the relay log IO_CACHE
while another thread is performing an FLUSH LOGS procedure.
      
FLUSH LOGS closes and reopens the relay log and while doing so it
(re)initializes its IO_CACHE. During this procedure the IO_CACHE
mutex is also reinitialized, which can cause problems if some
other thread (namely the IO THREAD) is concurrently accessing it
at the time .
      
This patch fixes the problem by extending the interface of the
flush_master_info function to also include a second paramater, 
"need_relay_log_lock", stating whether the thread should grab the 
relay log lock or not before actually flushing the relay log. 
Also, IO thread now calls flush_master_info with this flag set 
when it flushes master info with in the event read_event loop.

Finally, we also increase loop time in rpl_heartbeat_basic test 
case, so that the number of calls to flush logs doubles, stressing
this part of the code a little more.

mysql-test/suite/rpl/t/rpl_heartbeat_basic.test:
  Doubled the number of iterations on the FLUSH LOGS loop by
  doubling the time available to perform all iterations.
sql/repl_failsafe.cc:
  Updating flush_master_info call so that it uses two parameters
  instead of one.
sql/rpl_mi.cc:
  Updating flush_master_info call so that it uses two parameters
  instead of one.
sql/rpl_mi.h:
  Changed flush_master_info interface. Now takes a second parameter
  instead of just one. The second parameter is: need_lock_relay_log.
sql/rpl_rli.cc:
  Small fix in comment.
sql/slave.cc:
  Updating flush_master_info call so that it uses two parameters
  instead of one.
sql/sql_repl.cc:
  Updating flush_master_info call so that it uses two parameters
  instead of one.

1 files changed, 16 insertions, 3 deletions

diff --git a/sql/rpl_mi.cc b/sql/rpl_mi.cc
index e83e0ad0ba9..28b0af441f8 100644
--- a/sql/rpl_mi.cc
+++ b/sql/rpl_mi.cc
@@ -387,7 +387,7 @@ file '%s')", fname);
   mi->rli.is_relay_log_recovery= FALSE;
   // now change cache READ -> WRITE - must do this before flush_master_info
   reinit_io_cache(&mi->file, WRITE_CACHE, 0L, 0, 1);
-  if ((error=test(flush_master_info(mi, 1))))
+  if ((error=test(flush_master_info(mi, TRUE, TRUE))))
     sql_print_error("Failed to flush master info file");
   pthread_mutex_unlock(&mi->data_lock);
   DBUG_RETURN(error);
@@ -413,7 +413,9 @@ err:
      1 - flush master info failed
      0 - all ok
 */
-int flush_master_info(Master_info* mi, bool flush_relay_log_cache)
+int flush_master_info(Master_info* mi, 
+                      bool flush_relay_log_cache, 
+                      bool need_lock_relay_log)
 {
   IO_CACHE* file = &mi->file;
   char lbuf[22];
@@ -436,8 +438,19 @@ int flush_master_info(Master_info* mi, bool flush_relay_log_cache)
   */
   if (flush_relay_log_cache)
   {
+    pthread_mutex_t *log_lock= mi->rli.relay_log.get_log_lock();
     IO_CACHE *log_file= mi->rli.relay_log.get_log_file();
-    if (flush_io_cache(log_file))
+
+    if (need_lock_relay_log)
+      pthread_mutex_lock(log_lock);
+
+    safe_mutex_assert_owner(log_lock);
+    err= flush_io_cache(log_file);
+
+    if (need_lock_relay_log)
+      pthread_mutex_unlock(log_lock);
+
+    if (err)
       DBUG_RETURN(2);
   }