Race condition
A race condition or race hazard is the behavior of an electronics, software, or other system where the system's substantive behavior is dependent on the sequence or timing of other uncontrollable events. It becomes a bug when one or more of the possible behaviors is undesirable.
Mutual exclusion
This problem (called a "race condition") can be avoided by using the requirement of mutual exclusion to ensure that simultaneous updates to the same part of the list cannot occur.