What VxWorks primitives are used for mutual exclusion in Berkeley DB?
Mutexes inside of Berkeley DB use the basic binary semaphores in VxWorks. The mutexes are created using the FIFO queue type. • What are the implications of VxWorks’ mutex implementation using microkernel resources? On VxWorks, the semaphore primitives implementing mutexes consume system resources. Therefore, if an application unexpectedly fails, those resources could leak. Berkeley DB solves this problem by always allocating mutexes in the persistent shared memory regions. Then, if an application fails, running recovery or explicitly removing the database environment by calling the DB_ENV->remove method will allow Berkeley DB to release those previously held mutex resources. If an application specifies the DB_PRIVATE flag (choosing not to use persistent shared memory), and then fails, mutexes allocated in that private memory may leak their underlying system resources. Therefore, the DB_PRIVATE flag should be used with caution on VxWorks.
