Concurrency and Deadlocks Quiz

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Questions and Answers

What happens in a system with no preemption if a process holding resources requests another resource that is not immediately available?

All resources currently held are released (correct)

The process is allowed to keep the resources until the new one becomes available

The new resource is forcibly allocated to the process

The process is terminated and all resources are freed up

What action is taken if a process in a system with no preemption cannot immediately access a requested resource?

Released all held resources (correct)

Forced allocation of the requested resource

Kept holding the current resources

Paused the process temporarily

How can deadlock be avoided in a system where each process requests resources in an increasing order of enumeration?

By preempting processes requesting multiple resources

By randomly allocating resources to processes

By allowing processes to request any resource at any time

By imposing a total ordering of all resource types (correct)

What additional information does a system need to have to avoid deadlocks based on the sequence of requests from active processes?

Sequence of requests associated with each active process Signup and view all the answers

In what scenario can a process be restarted in a system with no preemption?

When it can regain its old resources and the new ones it requested Signup and view all the answers

Which situation can lead to a deadlock in disk sharing?

Competing processes sending conflicting commands to access a disk Signup and view all the answers

What can cause a deadlock in spooling?

Spooling system keeping partially completed output on disk Signup and view all the answers

In the case of deadlocks in a network, what can lead to a deadlock?

All available buffer space being filled with messages Signup and view all the answers

What is a common characteristic of deadlocks in multiple device allocation?

Several processes hold onto dedicated devices while others act similarly Signup and view all the answers

What situation can result in a deadlock in a shared spooling system?

Printer waiting for all job's output before printing Signup and view all the answers

In the context of deadlocks in disk sharing, what leads to conflicting commands?

Two processes waiting for I/O requests at different locations Signup and view all the answers

What is the primary cause of deadlocks in spooling systems?

Printer requiring all job's output for printing Signup and view all the answers

What can lead to deadlocks in a shared network environment?

No protocols to manage message flow Signup and view all the answers

What is a characteristic of a deadlock in disk sharing?

Each process is holding a resource and waiting for another resource held by another process Signup and view all the answers

In a spooling system, what happens if a program is in deadlock?

Other programs that require the resources held by the deadlock are put on hold Signup and view all the answers

What can lead to a deadlock in a network?

Processes requesting access to files they cannot release Signup and view all the answers

How does a deadlock in spooling differ from a deadlock in disk sharing?

In spooling, processes are blocked due to holding resources, while in disk sharing, they are blocked due to waiting for resources Signup and view all the answers

What is a common characteristic of deadlocks in spooling and network deadlocks?

They both occur due to processes blocking each other while holding resources Signup and view all the answers

What distinguishes deadlocks on file requests from deadlocks in databases?

File request deadlocks occur when jobs request files for execution, while database deadlocks involve processes accessing and locking records Signup and view all the answers

Study Notes

Deadlock in Systems

In a system with no preemption, if a process holding resources requests another resource that is not immediately available, it will block and wait for the requested resource to become available. The process will not be forcibly removed from its current state.
A process in a system with no preemption that cannot immediately access a requested resource will wait until the resource becomes available. The process will remain in a blocked state until the resource is released.
Deadlock can be avoided in a system where each process requests resources in an increasing order of enumeration by implementing a resource ordering protocol. This protocol ensures that if a process requests resource R1 then R2, any other process requesting resources will request R1 before R2 as well.
To avoid deadlocks based on the sequence of requests from active processes, the system needs to be aware of the current state of resource allocation and the order of resource requests from each process.

In a system with no preemption, a process can be restarted only if it is not holding any resources. If the process is holding a resource, it cannot be restarted until the resource is released.
A deadlock in disk sharing can occur when two or more processes are waiting for each other to release the same disk, leading to a circular dependency where no process can proceed.
Deadlock in disk sharing happens when conflicting commands are issued by processes. For example, one process may try to write to a file while another tries to read the same file.
A common characteristic of deadlocks in multiple device allocation is that they involve multiple resources (e.g., disk, tape drive, printer), and multiple processes competing for these resources.

Deadlock in Spooling

Deadlock in spooling can occur when a program is waiting for a resource that is being held by another program, and both programs are waiting for each other. This can happen, for example, when one program needs to read data from a file that is currently being written to by another program.
Deadlock in spooling can occur when two or more processes are waiting for the same spool file.
The primary cause of deadlocks in spooling systems is the lack of a centralized resource allocation mechanism. This allows for processes to acquire resources in a way that can lead to deadlocks.

Deadlock in Networks

Deadlocks in a network can occur when two or more devices are waiting for each other to transmit data. For instance, device A holds a resource needed by device B, and device B holds a resource needed by device A.
A characteristic of a deadlock in disk sharing is that it involves multiple processes waiting for each other to release a specific disk.
In a spooling system, if a program is in deadlock, it will be unable to proceed and will remain in a blocked state until the deadlock is resolved.
Deadlocks in a network can occur when two or more nodes are waiting for each other to send data through shared links. This can happen if two nodes try to use the same link at the same time, leading to a circular dependency where no node can proceed.

Comparing Deadlocks

A deadlock in spooling differs from a deadlock in disk sharing in the fact that spooling deadlocks usually involve multiple processes competing for a single shared resource, such as a spool file. Disk sharing deadlocks usually involve multiple processes competing for multiple shared resources, such as disks.
A common characteristic of deadlocks in both spooling and network scenarios is that they involve a circular dependency where resources are held by multiple processes, each waiting for a resource held by another. This creates a standstill where none of the processes can proceed.
Deadlocks on file requests differ from deadlocks in databases in that file requests typically involve low-level operations related to accessing a file on a disk. Deadlocks in databases, however, occur at a higher level, involving transactions and locks on data within the database.

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Description

Test your knowledge on concurrency issues in database systems, including locking, race conditions, and deadlocks. Learn about managing access to data at different levels of granularity and understanding the complexities that arise in multi-process environments.