maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Sergey!

On Mar 17, svoj@xxxxxxxxxxx wrote:
> revision-id: 93e746afb2d1a23cb933291ad736a20858b5ac3e
> parent(s): ccc7297fe94af1129c717f91d31fa075d54a0371
> committer: Sergey Vojtovich
> branch nick: mariadb
> timestamp: 2015-03-17 19:49:04 +0400
> message:
> 
> MDEV-7793 - Race condition between XA COMMIT/ROLLBACK and disconnect
> 
> XA COMMIT/ROLLBACK of XA transaction owned by different thread may access
> freed memory if that thread disconnects at the same time.
> 
> Also concurrent XA COMMIT/ROLLBACK of recovered XA transaction were not
> serialized properly.
> 
> diff --git a/sql/sql_class.cc b/sql/sql_class.cc
> index 3071ba6..f18231d 100644
> --- a/sql/sql_class.cc
> +++ b/sql/sql_class.cc
> @@ -5355,7 +5378,7 @@ bool xid_cache_insert(THD *thd, XID_STATE *xid_state)
>    switch (res)
>    {
>    case 0:
> -    xid_state->xid_cache_element->mark_initialized();
> +    xid_state->xid_cache_element->set(XID_cache_element::ACQUIRED);

Why not mark_acquired() here?
Can you be sure that no other thread has already acquired this
xid_cache_element after you've inserted it?

>      break;
>    case 1:
>      my_error(ER_XAER_DUPID, MYF(0));

Regards,
Sergei