Django DB transactions and deadlocks with multiple WSGI processes

When running Django with Gunicorn with multiple processes/workers I'm getting a deadlock issue with some of my manual MySQL database transactions.

    DatabaseError(1205, 'Lock wait timeout exceeded; try restarting transaction')

My setup uses multiple databases, and my function needs to be passed the database to use when it's called. For this reason, I can't use the standard [Django transaction decorators](https://docs.djangoproject.com/en/1.4/topics/db/transactions/) as the db needs to be hard-coded as an argument. I've inspected the decorator code to look at how transactions are managed, and my function looks like this:

    from django.db import connections

    def process(self, db, data):

        # Takeover transaction management

        connections[db].enter_transaction_management(True)

        connections[db].managed(True)

        # Process

        try:

            # do things with my_objects...

            for obj in my_objects:

                obj.save(using=db)

            connections[db].commit()

        except Exception as e:

            connections[db].rollback()

        finally:

            connections[db].leave_transaction_management()

Can anyone spot what may be going wrong here?

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