Tutorial Week 11

Questions

Recap any outstanding questions in last week's tutorial - especially Q8 and Q14 which were covered in lectures after the tutorial.

Q1: Describe programmed I/O and interrupt-driven I/O in the case of receiving input (e.g. from a serial port). Which technique normally leads to more efficient use of the CPU? Describe a scenario where the alternative technique is more efficient.

Q2: A device driver routine (e.g. read_block() from disk) is invoked by the file system code. The data for the filesystem is requested from the disk, but is not yet available. What do device drivers generally do in this scenario?

Q3: Describe how I/O buffering can be formulated as a bounded-buffer producer-consumer problem.

Q4: An example operating system runs its interrupt handlers on the kernel stack of the currently running application. What restriction does this place on the interrupt handler code? Why is the restriction required?