1.2 What is a Data Race?

The Thread Analyzer detects data-races that occur during the execution of a multi-threaded process. A data race occurs when:

• two or more threads in a single process access the same memory location concurrently, and

• at least one of the accesses is for writing, and

• the threads are not using any exclusive locks to control their accesses to that memory.

When these three conditions hold, the order of accesses is non-deterministic, and the computation may give different results from run to run depending on that order. Some data-races may be benign (for example, when the memory access is used for a busy-wait), but many data-races are bugs in the program.

The Thread Analyzer works on a multi-threaded program written using the POSIX thread API, Solaris thread API, OpenMP, Sun parallel directives, Cray parallel directives, or a mix of the above.