definition of soft/hard interrupts.

[Bahadir Balban]

Hi,

In "The design and implementation of 4.4BSD", the execution of
workqueues, some timer events and scheduling are referred to as
"software interrupts", as well as system calls. I thought only system
calls would be in "soft interrupt" category as they are initiated with
a software interrupt instruction.

By my definition, a hardware interrupt is one that is notified by the
interrupt controller, and to my knowledge, timer events are hardware
interrupts. Am I wrong?

There's also a softclock and hardclock defined. It is as if, an
interrupt handler for an interrupt reported on the controller, is
termed as "hard", but a low-priority workqueue initiated by a later
timer event is called as a "software interrupt" here. The distinction
here mainly being made by their "priority". Would you confirm this?

In my opinion this isn't the way to put it and software interrupts
should only mean interrupts initiated by interrupt instructions.

All this is mentioned in pp. 56-57 in the book and extends to other parts.

Many thanks for reading,
Bahadir