Alfranio Correia a0946fa3d1 BUG#50038 Deadlock on flush logs with concurrent DML and RBR ... In auto-commit mode, updating both trx and non-trx tables (i.e. issuing a mixed statement) causes the following sequence of events: 1 - "Flush trx changes" (MYSQL_BIN_LOG::write) - T1: 1.1 - mutex_lock (&LOCK_log) 1.2 - mutex_lock (&LOCK_prep_xids) 1.3 - increase prepared_xids 1.4 - mutex_unlock (&LOCK_prep_xids) 1.5 - mutex_unlock (&LOCK_log) 2 - "Flush non-trx changes" (MYSQL_BIN_LOG::write) - T1: 2.1 - mutex_lock (&LOCK_log) 2.2 - mutex_unlock (&LOCK_log) 3. "unlog" - T1 3.1 - mutex_lock (&LOCK_prep_xids) 3.2 - decrease prepared xids 3.3 - pthread_cond_signal(&COND_prep_xids); 3.4 - mutex_unlock (&LOCK_prep_xids) The "FLUSH logs" command produces the following sequence of events: 1 - "FLUSH logs" command (MYSQL_BIN_LOG::new_file_impl) - user thread: 1.1 - mutex_lock (&LOCK_log) 1.2 - mutex_lock (&LOCK_prep_xids) 1.3 - while (prepared_xids) pthread_cond_wait(..., &LOCK_prep_xids); 1.4 - mutex_unlock (&LOCK_prep_xids) 1.5 - mutex_unlock (&LOCK_log) A deadlock will arise if T1 flushes the trx changes and thus increases prepared_xids but before it is able to continue the execution and flush the non-trx changes, an user thread calls the "FLUSH logs" command and wait that the prepared_xids is decreased and gets to zero. However, T1 cannot proceed with the call to "Flush non-trx changes" because it will block in the mutex "LOCK_log" and by consequence cannot complete the execution and call the unlog to decrease the prepared_xids. To fix the problem, we ensure that the non-trx changes are always flushed before the trx changes. Note that if you call "Flush non-trx changes" and a concurrent "FLUSH logs" is issued, the "Flush non-trx changes" may block, but a deadlock will never happen because the prepared_xids will eventually get to zero. Bottom line, there will not be any transaction able to increase the prepared_xids because they will block in the mutex "LOCK_log" (MYSQL_BIN_LOG::write) and those that increased the prepared_xids will eventually commit and decrease the prepared_xids.		2010-01-05 16:55:23 +00:00
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r	BUG#50038 Deadlock on flush logs with concurrent DML and RBR	2010-01-05 16:55:23 +00:00
std_data	Bug#47323 : mysqlbinlog --verbose displays bad output when events contain subset of columns	2009-10-09 16:54:48 +08:00
t	Bug #47863 binlog_format should be writable only at transaction boundaries	2009-12-23 18:43:45 +08:00
combinations	WL#4350 Options in my.cnf style config file should not start with --	2008-09-05 15:31:09 +02:00