machine is in problem mode, the type of interrupt (if it is other than an
ing in the user's virtual machine). Control is transferred to the appropriate inter
rupt handler for
If the machine is in supervisor mode, the
branch is taken to the appropriate
If a timer interrupt occurs,
indicates time slice end for the running user. The clock comparator indicates that a
specified timer event occurred, such as midnight, scheduled shutdown, or user
event reached.
The external console interrupt invokes
3215 to an alternate operator's console.
A service signal is a class 24 external interrupt that is generated when either a log
ical device or the Maintenance and
pletion of an operation initiated by a program (in the case of the logical device
Control
GA22-
Synchronous Interrupts in an Attached Processor or Multiprocessor System
Real
Generally, when synchronous interrupts (such as program and
occur in an attached processor or multiprocessor system, the processing of the
interrupt can proceed without the global system lock for mainline, nonerror paths.
Otherwise, the global system lock is required. If the global system lock is needed
and it is already in use, the processing of the interrupt is deferred until the global
system lock is available. In this case, the interrupted processor attempts to run
another user.
In an attached processor configuration, only the main processor can receive real
processor are initialized to ones to enable interruptions from any available channel.
zeros. In a multiprocessor configuration, both processors can receive real
tialized to ones to enable interruptions from any available channel.
Interruption Handling 23