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BUG#54509: rpl_show_slave_running crashes the server sporadically

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Problem: SQL and IO thread were racing for the IO_CACHE. The former to
flush it, the latter to close it. In some cases this would cause the
SQL thread to lock an invalid IO_CACHE mutex (it had been destroyed by
IO thread). This would happen when SQL thread was initializing the
master.info

Solution: We solve this by locking the log and checking if it is
hot. If it is we keep the log while seeking. Otherwise we release it
right away, because a log can get from hot to cold, but not from cold
to hot.
This commit is contained in:
Luis Soares
2010-06-24 19:03:23 +01:00
parent 72584c312d
commit 16141e0c85
1 changed files with 22 additions and 0 deletions
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22
sql/rpl_mi.cc
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@ -164,7 +164,29 @@ int init_master_info(Master_info* mi, const char* master_info_fname,
*/
if (thread_mask & SLAVE_SQL)
{
bool hot_log= FALSE;
/*
my_b_seek does an implicit flush_io_cache, so we need to:
1. check if this log is active (hot)
2. if it is we keep log_lock until the seek ends, otherwise
release it right away.
If we did not take log_lock, SQL thread might race with IO
thread for the IO_CACHE mutex.
*/
mysql_mutex_t *log_lock= mi->rli.relay_log.get_log_lock();
mysql_mutex_lock(log_lock);
hot_log= mi->rli.relay_log.is_active(mi->rli.linfo.log_file_name);
if (!hot_log)
mysql_mutex_unlock(log_lock);
my_b_seek(mi->rli.cur_log, (my_off_t) 0);
if (hot_log)
mysql_mutex_unlock(log_lock);
}
DBUG_RETURN(0);
}