$[$Resource allocation graph$-$ concurrency$]$

Deadlock can be defined as the permanent blocking of a set of processes that either compete for

system resources or communicate with each other. A set of processes is deadlocked when each

process in the set is blocked awaiting an event $($typically the freeing up of some requested

resource$)$ that can only be triggered by another blocked process in the set. Deadlock is permanent

because none of the events is ever triggered. Unlike other problems in concurrent process

management, there is no efficient solution in the general case.

In the code below, four processes $($P$0,$ P$1,$ P$2,$ P$3)$ are competing for seven resources labelled A to

G$.$ Each resource has a single instance, except resource E which has $2$ instances.

Source: $($Kishinkwa$,2024)$

$2\mathrm{.}1$

a$.$ Suppose the following codes are scheduled for execution line by line from PO to P$3.$ Using a

resource allocation graph, show the possibility of a deadlock in this implementation.

$(10$ marks$)$

b$.$ Modify the order of some of the get requests to prevent the possibility of any deadlock.

$(5$ Marks$)$

c$.$ Is it possible that a resource deadlock involves multiple units of one type and a single unit of

another? If so$,$ give an example.

$(5$ marks$)$