For Solaris threads, a condition variable enables threads to atomically block until a condition is satisfied. The condition is tested under the protection of a mutex lock. When the condition is false, a thread blocks on a condition variable and atomically releases the mutex waiting for the condition to change. When another thread changes the condition, it can signal the associated condition variable to cause one or more waiting threads to wake up, reacquire the mutex, and re-evaluate the condition. Condition variables can be used to synchronize threads in this process and other processes if the variable is allocated in memory that is writable and shared among the cooperating processes and have been initialized for this behavior.