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, 3 insertions, 1 deletions

diff --git a/sql/rpl_mi.h b/sql/rpl_mi.h
index f822a6bc1b1..363c8d4e0b3 100644
--- a/sql/rpl_mi.h
+++ b/sql/rpl_mi.h
@@ -120,7 +120,9 @@ int init_master_info(Master_info* mi, const char* master_info_fname,
 		     bool abort_if_no_master_info_file,
 		     int thread_mask);
 void end_master_info(Master_info* mi);
-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);
 int change_master_server_id_cmp(ulong *id1, ulong *id2);
 
 #endif /* HAVE_REPLICATION */