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| author | unknown <guilhem@mysql.com> | 2004-07-30 00:53:25 +0200 |
|---|---|---|
| committer | unknown <guilhem@mysql.com> | 2004-07-30 00:53:25 +0200 |
| commit | d475643da872a78a8b9a4f806b768803959bbb69 (patch) | |
| tree | 397ba8915bf684bd260adc0419a320e31f309c4a /sql/log.cc | |
| parent | 382ff793bb52de384ce49074c61ce81fc2ce3236 (diff) | |
| download | mariadb-git-d475643da872a78a8b9a4f806b768803959bbb69.tar.gz | |
Avoiding a theoretically possible crash (pthread_mutex_lock(0)) which could (at least in POSIX Threads books)
happen on SMP machines, when a thread is going to wait on a condition and it is KILLed at the
same time.
Cleaning code a bit by adding a test in enter_cond() that we have the mutex (was already the case in all places
where it's called except one which is fixed here).
sql/log.cc:
safe_mutex_assert_owner() is now in THD::enter_cond()
sql/slave.cc:
lock mutex before waiting on condition.
sql/sql_class.cc:
THD::awake(): before locking the mutex, let's test it's not zero;
in theory indeed, the killer thread may see current_cond non-zero and current_mutex zero
(order of assignments is not guaranteed by POSIX).
A comment noting that there is still a small chance a KILL does not work and needs
being re-issued.
sql/sql_class.h:
Assert in enter_cond() that we have the mutex.
It is already the case in all places where we call enter_cond(), so better ensure it there.
Diffstat (limited to 'sql/log.cc')
| -rw-r--r-- | sql/log.cc | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/sql/log.cc b/sql/log.cc index 559d30f28ba..a0e2196cc59 100644 --- a/sql/log.cc +++ b/sql/log.cc @@ -1544,7 +1544,6 @@ bool MYSQL_LOG::write(THD *thd,const char *query, uint query_length, void MYSQL_LOG:: wait_for_update(THD* thd, bool master_or_slave) { - safe_mutex_assert_owner(&LOCK_log); const char* old_msg = thd->enter_cond(&update_cond, &LOCK_log, master_or_slave ? "Has read all relay log; waiting for \ |