Attention handling

When the runtime option INTERRUPT(ON) is specified, the Language Environment condition manager issues a STAX macro, which requests attention interrupts to be directed to a STAX exit.

In the CAA at offset X'120', label CEECAAATTN, is initially set to the address of a routine that runs a BR 14.

If an attention interrupt occurs and the STAX exit is entered, the STAX exit changes the address of the routine at CEECAAATTN to a routine that issues a CALL CEESGL raising the ATTENTION condition.

Polling code is contained in both library- and compiler-generated code and is the following code sequence; there is no parameter for this routine and R1 is not used:

L    15,CEECAAATTN
BALR 14,15

When polling code calls the routine that calls CEESGL, the attention condition is raised. Condition handling proceeds with the defined sequence of condition handling events, as if a synchronous condition were raised.