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, 2 insertions, 2 deletions

diff --git a/sql/slave.cc b/sql/slave.cc
index 27f87d18800..3678c2497de 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -1726,7 +1726,7 @@ static void write_ignored_events_info_to_relay_log(THD *thd, Master_info *mi)
                    " to the relay log, SHOW SLAVE STATUS may be"
                    " inaccurate");
       rli->relay_log.harvest_bytes_written(&rli->log_space_total);
-      if (flush_master_info(mi, 1))
+      if (flush_master_info(mi, TRUE, FALSE))
         sql_print_error("Failed to flush master info file");
       delete ev;
     }
@@ -3047,7 +3047,7 @@ Stopping slave I/O thread due to out-of-memory error from master");
         goto err;
       }
 
-      if (flush_master_info(mi, 1))
+      if (flush_master_info(mi, TRUE, TRUE))
       {
         sql_print_error("Failed to flush master info file");
         goto err;