help needed: hsqldb shutdown race condition, how to fix without deadlock

[Noel Grandin]

On 2015-06-02 03:07 PM, Lionel Elie Mamane wrote:
> Hi,
>
> I found a race condition between
>
> 1) connectivity::hsqldb::ODriverDelegator::flushConnections()
>     (in file connectivity/source/drivers/hsqldb/HDriver.cxx around line 620)
>     walking over m_aConnections
>
> 2) connectivity::hsqldb::ODriverDelegator::disposing()
>     (same file around line 565)
>     calling
>
>          m_aConnections.clear();
>          TWeakPairVector().swap(m_aConnections);
>
>     which invalidates the iterators used by flushConnection()
>
> Plus also probably, race condition between flushConnections() calling
> flush() and disposing() disposing the underlying connection (although
> this is probably handled correctly by the exception catching...).
>

I would suggest something like this in ODriverDelegator::flushConnections():

     take_mutex();
     std::vector<Connection> tmp = m_aConnections;
     release_mutex();
     for (Connection conn : tmp)
         conn.flush();

so that the mutex is not held during the problematic phase