Message Passing

The message passing is the only way provided by the kernel to communicate with other tasks.

The IPC operations, sending and receiving a message, are synchronous (i.e. blocking). The desitnation of a message is specified by task ID and Resea does not provide the notion of channel or port of IPC for simplicity.

For more details, see IPC API.

Why not asynchronous?

Synchronous IPC is good for performance and for the separation of mechanism and policy. Survey L4 microkernels if you're interested in.

Futhermore, syncronous IPC siginificantly simplifies the complexity of a multi-server OS like Resea and makes easy to debug your code.

Message

A message is fixed sized and consists of the following fields:

  • The type of message (e.g. FS_READ_MSG).
  • The sender task ID.
  • The fixed-sized payload (less than 256 bytes, depends on arch).
  • The out-of-line payload for large data.

We use our own Interface Definition Language to generate message definitions.