Race Condition

File systems
In file systems, two or more programs may "collide" in their attempts to modify or access a file, which could result in data corruption. File locking provides a commonly-used solution. A more cumbersome remedy involves organizing the system in such a way that one unique process (running a daemon or the like) has exclusive access to the file, and all other processes that need to access the data in that file do so only via interprocess communication with that one process (which of course requires synchronization at the process level).

A different form of race condition exists in file systems where unrelated programs may affect each other by suddenly using up available resources such as disk space (or memory, or processor cycles). Software not carefully designed to anticipate and handle this rare situation may then become quite fragile and unpredictable. Such a risk may be overlooked for a long time in a system that seems very reliable. But eventually enough data may accumulate or enough other software may be added to critically destabilize many parts of a system. Probably the best known example of this occurred with the near-loss of the Mars Rover "Spirit" not long after landing, but this is a commonly overlooked hazard in many computer systems. A solution is for software to request and reserve all the resources it will need before beginning a task; if this request fails then the task is postponed, avoiding the many points where failure could have occurred. (Alternately, each of those points can be equipped with error handling, or the success of the entire task can be verified afterwards, before continuing on.) A more common but incorrect approach is to simply verify that enough disk space (for example) is available before starting a task; this is not adequate because in complex systems the actions of other running programs can be unpredictable.

Networking
In networking, consider a distributed chat network like IRC, where a user acquires channel-operator privileges in any channel he starts. If two users on different servers, on different ends of the same network, try to start the same-named channel at the same time, each user's respective server will grant channel-operator privileges to each user, since neither server will yet have received the other server's signal that it has allocated that channel. (Note that this problem has been largely solved by various IRC server implementations.)

In this case of a race condition, the concept of the "shared resource" covers the state of the network (what channels exist, as well as what users started them and therefore have what prk operation). Where users find such a solution unacceptable, a pragmatic solution can have the system 1) recognize when a race condition has occurred; and 2) repair the ill effects.

This Module
Due to database concurrency issues (fixed)