System test is hanging due to read/write locking

[mantid-builder]

Original Reporter: @jzikovsky

Original Owner: @jzikovsky

Here is the smallest code to reproduce the problem:

LoadEventNexus(OutputWorkspace="EQSANS_4061_event", Filename="EQSANS_4061_event.nxs")
EQSANSNormalise(InputWorkspace="EQSANS_4061_event", NormaliseToBeam='0')

The issue is that there is a parent python algorithm (EQSANSNormalise) that calls child algorithms (Scale) but these are not marked as such.

The way read/write locking works for C++ algorithms with children is:

• The parent algorithm locks the input/output workspaces
• The child algorithms do NOT do any locking.

With the EQSANSNormalise, it has its InputWorkspace erroneously set as "Input" (not InOut which is what it really is).

• EQSANSNormalise read-locks the workspace
• Then Scale tries to write-lock, so it hangs.

If EQSANSNormalise has its InputWorkspace set as InOut, it throws an exception when trying to double-write-lock.

So Martyn, what I need to do is to have the algorithms called in a Python algorithm to be set as "child". Do you know how to do that?

[mantid-builder]

This issue was originally trac ticket 4752