diff --git a/sql/slave.h b/sql/slave.h index 2b1af08fb7a..778ddf2ec72 100644 --- a/sql/slave.h +++ b/sql/slave.h @@ -171,31 +171,10 @@ typedef struct st_relay_log_info Handling of the relay_log_space_limit optional constraint. ignore_log_space_limit is used to resolve a deadlock between I/O and SQL threads, the SQL thread sets it to unblock the I/O thread and make it - temporarily forget about the constraint. It is declared volatile because we - have this loop in the I/O thread (slave.cc): - while (rli->log_space_limit < rli->log_space_total && - !(slave_killed=io_slave_killed(thd,mi)) && - !rli->ignore_log_space_limit) - pthread_cond_wait(&rli->log_space_cond, &rli->log_space_lock); - According to Monty, on some systems pthread_cond_wait() could be inline, - and so the loop be optimized by the compiler, so rli->ignore_log_space_limit - could be considered constant and the loop never ends, even if the SQL thread - has set rli->ignore_log_space_limit to 1 (and called - pthread_cond_broadcast()) to break the loop in the I/O thread. - By declaring it volatile, we are sure that the variable will not be - considered constant and that the loop can be broken. - This is the same for all bool variables used by a thread to inform another - thread that something has changed: thd->killed, rli->abort_slave, - MYSQL_LOG::log_type; they are all volatile. - Quoting: - while (a>0) { wait_for_condition } - here a should be volatile ? - serg: in most system no, but on some yes - on what systems ? - On any system where pthread_mutex is a macro. + temporarily forget about the constraint. */ ulonglong log_space_limit,log_space_total; - volatile bool ignore_log_space_limit; + bool ignore_log_space_limit; /* InnoDB internally stores the master log position it has processed