17
votes
Accepted
Why unsafe state not always cause deadlock?
Deadlock means something specific: there are two (or more) processes that are currently blocked waiting for each other.
In an unsafe state you can also be in a situation where there might be a ...
- 17.6k
12
votes
Accepted
Does Deadlock imply Starvation
You should first state the deadlock freedom property and the starvation freedom property more precisely.
I use the definition in the Book: The Art of Multiprocessor Programming; Section 2.2.
Freedom ...
- 9,461
10
votes
Why unsafe state not always cause deadlock?
Just to expound on what Wandering Logic was saying.
Say I have two threads that both need access to X and Y, and have no synchronization and no mechanism to fix deadlock. This is unsafe, as one could ...
- 1,239
10
votes
Accepted
Minimum number of processes for the deadlock?
I agree that no deadlock is possible here. If there are three or fewer processes, there clearly cannot be a deadlock because there are enough resources for every process to just hold two resources the ...
- 81.4k
6
votes
Accepted
How to satisfy bounded waiting in case of deadlock?
You are correct.
Consider the simple synchronization algorithm which denies entry to all processes.
In this case we have both deadlock and bounded waiting, since any process $p$ is not bypassed by ...
- 13.3k
5
votes
Accepted
How does lack of deadlock relate to computability in process calculi?
I think you are asking about expressivity of concurrent programming languages. This is a deep and not well-understood field. For example you say that "the $\pi$-calculus [...] has the power to ...
- 8,308
4
votes
Accepted
What is the difference between "deadlock prevention" and "deadlock avoidance"
It seems that deadlock prevention and deadlock avoidance are two names for the same concept. Indeed, the Wikipedia section on deadlock avoidance has been marked as redundant. While the distinction ...
- 274k
4
votes
How probable is a deadlock in the dining philosophers problem
the dining philosopher problem seems to be somewhat of a pedagogical "toy" example of concurrency and (dead)locking concepts for educational purposes. however it is studied seriously in some ...
- 11k
4
votes
When do deadlocks occur?
All 4 conditions must be satisfied at the same time.
Hold and Wait
Non-preemption of resources
Mutual Exclusion
Circular wait
In case of single instance of resources:
Cycle in resource allocation ...
4
votes
Accepted
Why deadlock in cigarette smokers problem
Agent A consumes agentSem, and produces tobacco and paper.
That might make Smoker I smoke but he is late: Smoker II already took the paper and Smoker III took tobacco.
Now, all the smokers are stuck,...
- 14.4k
4
votes
Accepted
Provide some help regarding the "Dining Philosophers Problem"?
Righties: will never try to acquire the left fork before they have the right one.
Lefties: will never try to acquire the right fork before they have the left one.
Deadlock: Assume that you reached ...
- 13.3k
4
votes
Accepted
Bounded waiting and starvation free in critical section problem
No, starvation-free doesn't imply bounded waiting.
For instance, consider a procedure that never even attempts to acquire any lock; but the amount of time it takes is variable and can be arbitrarily ...
D.W.♦
- 154k
3
votes
Accepted
A Dead-lock in an Operating System is
Your attempt "If a process is unable to change its state indefinitely because the resources requested by it are being used by another waiting process, then the system is said to be in a deadlock." is ...
- 27.7k
3
votes
Accepted
Is Bounded Waiting satisfied for this 2 process Solution?
In the following, I treat the first two statements acquire(lock1) acquire(lock2) as "trying", the middle two statements ...
- 9,461
3
votes
Is bounded waiting satisfied in the 2 Process Solution?
A little remark first: The bounded waiting (BW) property is defined with respect to algorithms, which is in turn defined as a set of concrete executions. Thus, we cannot conclude whether an algorithm ...
- 9,461
3
votes
difference between deadlock avoidance and detection
Simply to put
Deadlock avoidance: you employ some methods to avoid the deadlock ,but prevention is more restrictive than avoidance.
Deadlock detection: Here only the detection only takes place ...
3
votes
For a given certain situation how to prove that the system will never get into the state of Deadlock
The question in the given situation is equivalent to the question: is it possible to create or to design a system such that m processes sharing n resources of the same type may enter a deadlock state ...
3
votes
How probable is a deadlock in the dining philosophers problem
I don't know what algorithm the philosophers follow, but let's assume that deadlock is reached if all philosophers try to start eating at the very same time. Since your time is discrete, under any ...
- 274k
3
votes
Accepted
Bankers Algorithm-Is the system in safe state?
you can say there is no deadlock if there is a safe sequence for the completion, after $P1$ request is granted there must be a safe sequence where by which every process is completed.
...
3
votes
Accepted
Is this solution to the dining philosopher's problem entirely valid?
The description of an altruistic philosopher given in this answer, that you quoted in your question, is slightly imprecise. What it really is going on is that:
A possible approach for avoiding ...
- 146
3
votes
A real life system that faces and solves the dining philosophers problem
The dining philosopher's problem is a worst case scenario used to illustrate issues in algorithms. It's a test case. You probably won't find a static one-to-one mapping between it and a real world ...
- 12.6k
3
votes
Accepted
In Operating Systems, I can't understand why deadlock happens, why does a process not let go of a resource when it is done using it?
To answer part of your question: Processes are not smart. Processes just execute the code of their program, so if the program of P1 has not been written to release R1 when it's done with it, it won't ...
- 27.4k
3
votes
Accepted
Deadlocks: Why if 2 threads are waiting for a lock from each other results in a deadlock?
The situation you are describing is not a deadlock.
A deadlock would be more like this:
Both Thread A and Thread B require both Lock 1 and Lock 2.
Thread A first acquires Lock 1, then Lock 2.
Thread ...
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2
votes
Accepted
Falsifying the "Circular Wait" Condition - Deadlock Prevention
It's fixed. Your example violates the protocol. If the process needs mutually exclusive access to both the tape drive and the disk drive, then it needs to take locks in increasing order, i.e. first ...
2
votes
Accepted
Does the following modified Two-Phase Locking protocol ensure serializability and freedom from deadlock?
The question is not clear about the details, but assuming said resources are always locked-then-accessed sequentially, then a deadlock is not possible to occur. Since the locks are always obtained in ...
- 191
2
votes
When will deadlock occur in this producer-consumer code
It will be caused as follows:
Both processes blocked at the end, hence deadlocked.
- 1,745
2
votes
Accepted
How are semaphores and test-and-set instructions connected?
Semaphores are an abstract mechanism to control access to a shared resource. Other such mechanisms exist, for example locks and monitors. These are the counterparts of abstract data structures – they ...
- 274k
1
vote
Does Deadlock imply Starvation
Starvation, as the name suggested, is when a process can acquire the lock, but it is being overlooked. It starves even with resources being available.
There is no deadlock in starvation; each process ...
- 111
1
vote
Accepted
Deadlock not possible?
Lets say for the sake of argument we have 6 units of memory available and three processes in a current state where each holds 2 resources. Each process needs 3 resources to finish and release its ...
- 1,602
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