INTERRUPT(3CC4)INTERRUPT(3CC4)NAMEinterrupt Interrupt_handler - signal handling for the task library
SYNOPSIS
#include <task.h>
class Interrupt_handler : public object {
public:
// exported constructor
Interrupt_handler(int signo);
// exported virtual function
virtual int pending();
private:
// private virtual function
virtual void interrupt();
};
DESCRIPTION
Class Interrupt_handler provides a way for a task to wait for an exter‐
nal Unix signal. It is derived from class object so that tasks may
wait on a handler object.
Interrupt_handler ih(signo);
Constructs a new interrupt handler ih, which will wait for sig‐
nal number signo (see signal(3c)). When that signal occurs, the
private virtual function interrupt() is called immediately, via
the usual Unix signal mechanism. When the function returns, the
task which was interrupted resumes. That is, interrupts do not
cause preemption within the task model.
A special task, the interrupt alerter, is automatically created
by the task system. When a running task is suspended and an
interrupt has occurred since the last task suspension, the
interrupt alerter is scheduled. The alerter alerts the Inter‐
rupt_handlers associated with any interrupts which have occured
since the last time the alerter ran. Any tasks waiting for such
handlers therefore become runnable.
In the absence of any interrupt handlers, the scheduling process
terminates when there are no more tasks to be run. So long as
there are any interrupt handlers, scheduling will not terminate,
but will wait indefinitely for any interrupts which may occur.
int i = ih.pending();
Always returns ``true'' (non-zero) except the first time it is
called after an interrupt occurs.
void interrupt()
This is a private virtual function. The base-class version does
nothing. Normally you will derive a class from Interrupt_han‐
dler and define this function to do whatever is appropriate for
that class. See the tutorial for an example.
DIAGNOSTICS
See task(3CC4).
SEE ALSOtask.intro(3CC4), queue(3CC4), task(3CC4), tasksim(3CC4), and sig‐
nal(3c).
08 August 2000 INTERRUPT(3CC4)
