A spooling system (Figure 6.17) consists of an input process I, a user process P, and an o...

A spooling system (Figure 6.17) consists of an input process I, a user process P, and an output process O connected by two buffers. The processes exchange data in blocks of equal size. These blocks are buffered on a disk using a floating boundary between the input and the output buffers, depending on the speed of the processes. The communication primitives used ensure that the following resource constraint is satisfied:

i + o ≤ max

where

max = maximum number of blocks on disk

i = number of input blocks on disk

o = number of output blocks on disk

The following is known about the processes:

1. As long as the environment supplies data, process I will eventually input it to the disk (provided disk space becomes available).

2. As long as input is available on the disk, process P will eventually consume it and output a finite amount of data on the disk for each block input (provided disk space becomes available).

3. As long as output is available on the disk, process O will eventually consume it.

Show that this system can become deadlocked.

Figure 6.17 A Spooling System