Comment 15 for bug 724396

Yes, you are right. The proposed way breaks simulations (--check does not path with j>1).

I have done locks in non-parallel implementation, and the performance goes down, as you said:

-j Parallel Non-Parallel %
------------------------------------
1 997 1002 -0.5
2 821 842 -2.6
3 764 825 -8
4 752 908 -20.7
5 745 1132 -51.9
6 742 1180 -59