A system and method are provided to avoid deadlocks when performing non-atomic operations on data in a shared memory accessed by multiple processors, whereby the shared memory sends messages to implement a split lock. Via the messages, the requesting processor is granted exclusive access to the shared memory so that no other processor may access the same data until after the non-atomic operation has completed. The messages used to avoid the deadlock include a split lock request, a lock message, a grant message, a gone idle message and a release idle message. By using the above messages, the system accepts requests from multiple processors for exclusive access to memory, orders all of the requests, and awards exclusive access to the first processor to make a request. The system can include a cache memory, associated with a requesting processor, which sends a lock request to the main memory in response to a split lock request from a requesting processor.