Mesa Semantics

state

ready

to (re)enter

waiting

wait()

(exit)

(enter)

Mesa semantics: the signaled thread transitions back to the ready state (Nachos, Topaz, Java).

signal()

(Mesa)

BUT: the signaled thread must examine the monitor state again after the wait, as the state may have changed since the signal.

Suppose again that purple signals blue in the original example.

There is no suspended state: the signaler continues until it exits the monitor or waits.

The signaled thread contends with other ready threads to (re)enter the monitor and return from wait.

Mesa semantics are easier to understand and implement...

Loop before you leap!