MESSAGE PASSING USING SHARED MEMORY OF A COMPUTER

A lock-free mechanism is provided for successfully passing messages between processes even if a process is preempted while sending or receiving a message. Messages are communicated between processes using a mailbox data structure stored in memory shared by the processes, without the use of locks or other mutual exclusion entities that would otherwise limit concurrent delivery and receipt of messages placed in the data structure. The data structure in the illustrative embodiment includes one or more message slots for storing messages placed in the data structure and a number of state variables for inserting messages into and removing messages from the message slots. A process sends or retrieves messages by manipulating the state variables using indivisible atomic operations. This ensures that a process cannot be preempted from message passing until it finishes executing the atomic instruction. The method and mechanism have particular value in distributed shared memory (DSM) and non-uniform memory access (NUMA) machines.