GATE CS Deadlock questions

With respect to deadlocks in an operating system, which of the following statements is/are FALSE?

Consider a system consisting of $k$ instances of a resource $R$, being shared by $5$ processes. Assume that each process requires a maximum of two instances of resource $R$ and a process can request or release only one instance at a time. Further, a process can request the second instance of the resource only after acquiring the first instance. The …

$P=\left\{P_{1}, P_{2}, P_{3}, P_{4}\right\}$ consists of all active processes in an operating system. $R=\left\{R_{1}, R_{2}, R_{3}, R_{4}\right\}$ consists of single instances of distinct types of resources in the system. The resource allocation graph has the following assignment and claim edges. Assignment edges: …

Which of the following statements is/are $\text{TRUE}$ with respect to deadlocks?

Consider a computer system with multiple shared resource types, with one instance per resource type. Each instance can be owned by only one process at a time. Owning and freeing of resources are done by holding a global lock $(L)$. The following scheme is used to own a resource instance: function OWNRESOURCE(Resource R) Acquire lock L // a global lock if R …

Consider the following snapshot of a system running $n$ concurrent processes. Process $i$ is holding $X_i$ instances of a resource $R$, $1 \leq i \leq n$. Assume that all instances of $R$ are currently in use. Further, for all $i$, process $i$ can place a request for at most $Y_i$ additional instances of $R$ while holding the $X_i$ …

In a system, there are three types of resources: $E, F$ and $G$. Four processes $P_0$, $P_1$, $P_2$ and $P_3$ execute concurrently. At the outset, the processes have declared their maximum resource requirements using a matrix named Max as given below. For example, Max[$P_2, F$] is the maximum number of instances of $F$ that $P_2$ would …

Consider a system with $3$ processes that share $4$ instances of the same resource type. Each process can request a maximum of $K$ instances. Resources can be requested and releases only one at a time. The largest value of $K$ that will always avoid deadlock is ___

A system shares $9$ tape drives. The current allocation and maximum requirement of tape drives for that processes are shown below: …

A system has $6$ identical resources and $N$ processes competing for them. Each process can request at most $2$ resources. Which one of the following values of $N$ could lead to a deadlock?

Consider the following policies for preventing deadlock in a system with mutually exclusive resources. Process should acquire all their resources at the beginning of execution. If any resource is not available, all resources acquired so far are released. The resources are numbered uniquely, and processes are allowed to request for resources only in …

An operating system uses the Banker's algorithm for deadlock avoidance when managing the allocation of three resource types $X, Y,$ and $Z$ to three processes $P0, P1,$ and $P2.$ The table given below presents the current system state. Here, the Allocation matrix shows the current number of resources of each type allocated to each process and the Max …

A system contains three programs and each requires three tape units for its operation. The minimum number of tape units which the system must have such that deadlocks never arise is _________.

Three concurrent processes $X$, $Y$, and $Z$ execute three different code segments that access and update certain shared variables. Process $X$ executes the $P$ operation (i.e., $wait$) on semaphores $a$, $b,$ and $c$; process $Y$ executes the $P$ operation on semaphores $b$, $c,$ and $d$; process $Z$ executes the $P$ …

A system has $n$ resources $R_0, \dots,R_{n-1}$, and $k$ processes $P_0, \dots, P_{k-1}$. The implementation of the resource request logic of each process $P_i$ is as follows: $\text{if} (i\%2==0) \{$ $\quad\text{if} (i<n) \text{ request } R_i;$ $\quad\text{if} (i+2 < n) \text{ request } R_{i+2}; \}$ $\text{else} \{$ …

Consider a system with $4$ types of resources $R1$ ($3$ units), $R2$ ($2$ units), $R3$ ($3$ units), $R4$ ($2$ units). A non-preemptive resource allocation policy is used. At any given instance, a request is not entertained if it cannot be completely satisfied. Three processes $P1$, $P2$, $P3$ request the resources as follows if …

Which of the following is NOT true of deadlock prevention and deadlock avoidance schemes?

A single processor system has three resource types $X, Y$ and $Z$, which are shared by three processes. There are $5$ units of each resource type. Consider the following scenario, where the column alloc denotes the number of units of each resource type allocated to each process, and the column request denotes the number of units of each resource type …

Consider the following snapshot of a system running $n$ processes. Process $i$ is holding $x_i$ instances of a resource $R$, $1\leq i\leq n$ . Currently, all instances of $R$ are occupied. Further, for all $i$, process $i$ has placed a request for an additional $y_i$ instances while holding the $x_i$ instances it already has. There are …

Suppose $n$ processes, $P_1, \dots P_n$ share $m$ identical resource units, which can be reserved and released one at a time. The maximum resource requirement of process $P_i$ is $s_i$, where $s_i > 0$. Which one of the following is a sufficient condition for ensuring that deadlock does not occur?