diff options
Diffstat (limited to 'sql/ha_innodb.cc')
| -rw-r--r-- | sql/ha_innodb.cc | 48 |
1 files changed, 34 insertions, 14 deletions
diff --git a/sql/ha_innodb.cc b/sql/ha_innodb.cc index e330a0b532f..194c8b558f0 100644 --- a/sql/ha_innodb.cc +++ b/sql/ha_innodb.cc @@ -313,6 +313,35 @@ convert_error_code_to_mysql( } /***************************************************************** +If you want to print a thd that is not associated with the current thread, +you must call this function before reserving the InnoDB kernel_mutex, to +protect MySQL from setting thd->query NULL. If you print a thd of the current +thread, we know that MySQL cannot modify thd->query, and it is not necessary +to call this. Call innobase_mysql_end_print_arbitrary_thd() after you release +the kernel_mutex. +NOTE that /mysql/innobase/lock/lock0lock.c must contain the prototype for this +function! */ +extern "C" +void +innobase_mysql_prepare_print_arbitrary_thd(void) +/*============================================*/ +{ + VOID(pthread_mutex_lock(&LOCK_thread_count)); +} + +/***************************************************************** +Relases the mutex reserved by innobase_mysql_prepare_print_arbitrary_thd(). +NOTE that /mysql/innobase/lock/lock0lock.c must contain the prototype for this +function! */ +extern "C" +void +innobase_mysql_end_print_arbitrary_thd(void) +/*========================================*/ +{ + VOID(pthread_mutex_unlock(&LOCK_thread_count)); +} + +/***************************************************************** Prints info of a THD object (== user session thread) to the standard output. NOTE that /mysql/innobase/trx/trx0trx.c must contain the prototype for this function! */ @@ -329,15 +358,6 @@ innobase_mysql_print_thd( thd = (const THD*) input_thd; -/* We cannot use LOCK_thread_count to protect this operation because we own -the InnoDB kernel_mutex when we enter this function, but in freeing of a -THD object, MySQL first reserves LOCK_thread_count and AFTER THAT InnoDB -reserves kernel_mutex when freeing the trx object => a deadlock can occur. -The solution is for MySQL to use a separate mutex to protect thd->query and -thd->query_len. Someone should do that! This bug has been here for 3 years! - - VOID(pthread_mutex_lock(&LOCK_thread_count)); */ - fprintf(f, "MySQL thread id %lu, query id %lu", thd->thread_id, thd->query_id); if (thd->host) { @@ -367,14 +387,16 @@ thd->query_len. Someone should do that! This bug has been here for 3 years! len = thd->query_length; if (len > 300) { - len = 300; /* A TEMPORARY SOLUTION: print at most + len = 300; /* ADDITIONAL SAFETY: print at most 300 chars to reduce the probability of - a seg fault in a race */ + a seg fault if there is a race in + thd->query_len in MySQL; on May 13, + 2004 we do not know */ } for (i = 0; i < len && s[i]; i++); - memcpy(buf, s, i); /* use memcpy to reduce the timeframe + memcpy(buf, s, i); /* Use memcpy to reduce the timeframe for a race, compared to fwrite() */ buf[300] = '\0'; @@ -383,8 +405,6 @@ thd->query_len. Someone should do that! This bug has been here for 3 years! } putc('\n', f); - -/* VOID(pthread_mutex_unlock(&LOCK_thread_count)); */ } /************************************************************************* |