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MDEV-7888, MDEV-7929: Parallel replication hangs sometimes on ANALYZE TABLE or DDL

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The hangs occur when the group_commit_orderer object is freed before the last
mark_start_commit() call on it - this loses the wakeup to other waiting worker
threads, causing them to hang until killed manually.

The object was freed because wakeup_subsequent_commits() was called two early
in two places. For MDEV-7888, during ANALYZE TABLE, and for MDEV-7929 during
record_gtid() after processing a DDL event. The group_commit_orderer object
can be freed when its last transaction has called wait_for_prior_commit().

Fix by implementing a suspend/resume mechanism for wakeup_subsequent_commits()
that can be used in places where a transaction is committed without this being
the commit of the actual replication event group.

Also add a protection mechanism (that asserts in debug builds) which can
prevent the too-early free and hang if other similar bugs should remain in
other parts of the code.
This commit is contained in:
Kristian Nielsen
2015-04-08 11:01:18 +02:00
parent 880f2273fd
commit 3b961347db
7 changed files with 231 additions and 3 deletions
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9
sql/sql_class.h
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@ -3682,6 +3682,15 @@ public:
if (wait_for_commit_ptr)
wait_for_commit_ptr->wakeup_subsequent_commits(wakeup_error);
}
wait_for_commit *suspend_subsequent_commits() {
wait_for_commit *suspended= wait_for_commit_ptr;
wait_for_commit_ptr= NULL;
return suspended;
}
void resume_subsequent_commits(wait_for_commit *suspended) {
DBUG_ASSERT(!wait_for_commit_ptr);
wait_for_commit_ptr= suspended;
}
private: