The OS implements interrupt handlers for floppies, like when the drive door is closed or when a floppy is ejected.
22.
A data acquisition device driver has an interrupt handler which uses data from the output pages and stores data in the input pages.
23.
They were used in implementing the FIS instruction subset, with instructions processed not in microcode, but as interrupt handlers in shadow ROM.
24.
If the interrupt handler does not modify the saved status register, returning from the interrupt will then resume the original low-power mode.
25.
For this reason it can be problematic when an interrupt handler calls an OS function while the application is in the act of also doing so.
26.
The OS function called from an interrupt handler could find the object database to be in an inconsistent state because of the application's update.
27.
But if the function is used in a reentrant interrupt handler and a second interrupt arises inside the function, the second routine will hang forever.
28.
An example situation when a double fault would occur is when an interrupt is triggered but the segment in which the interrupt handler resides is invalid.
29.
Locks don't work for sharing data between interrupt handlers and ordinary code because you deadlock if a thread is interrupted while holding the lock.
30.
For example, most processors allow programs to disable interrupts, putting off the execution of interrupt handlers, in order to protect critical sections of code.
