When two activities run concurrently, we say there is potential interference if there is some shared data that is accessed by both activities, and where at least one of the activities can modify this data. Some say “We only need to prevent concurrency in cases where the concurrent activities can both modify some shared data.”

Why is this view is incorrect?

  • Is this an exam / interview question?
    – Dave M
    Apr 25, 2016 at 14:19

1 Answer 1


Consistency. Suppose two pieces of data need to be mutually consistent. If the update activity changes those two pieces of data in a non-atomic way, it is possible that the reading activity will read the data when only one piece has been updated.

  • yes. However the somewhat confusing question asks why the view is incorrect about cases where the concurrent activity can both modify some shared data. sort of like a double negative perhaps Apr 20, 2017 at 12:13

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