If the code has race conditions [1], then an MP system can certainly
bring out the worst in the software. It's not because the timeslice
changes, it's because threads really do execute concurrently (instead
of just appearing to execute concurrently on uniproc system).

One approach would be to scour through the code and place locks and
Monitors where appropriate, but a better approach might be to get rid
of the static state where ever possible. It's hard to find all the
places you need a lock. It's easier to write the code so that you
don't have to worry about a lock, or let another service (like a
database) worry about locking.

[1] http://en.wikipedia.org/wiki/Race_condition
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Scott
http://www.OdeToCode.com/blogs/scott/