daverave:

In general, you can avoid locking if you can guarantee that there would be no overlap. However, I'd argue against it:

• First, it's difficult to make those sorts of guarantees, especially as the constraints get more complicated.
• Second, during maintenance, it's amazingly simple to break the guarantee.

The second reason is especially pernicious, as thread interaction bugs can raise their heads infrequently. The interval between creating the bug and being bitten by it can hide the cause of the bug, as you wouldn't necessarily remember the change you made four months ago!

...roboticus