Questions tagged [deadlocks]

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5answers
13k views

Why unsafe state not always cause deadlock?

I was reading Operating Systems by Galvin and came across the below line, Not all unsafe states are deadlock, however. An unsafe state may lead to deadlock Can someone please explain how ...
7
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1answer
638 views

Inconsistent state of a lock

I'm reading The Art of Multiprocessor programming and trying to understand their concept of inconsistent locks. Specifically, on page 37, the definition 2.8.1 of an inconsistent lock is not clear to ...
6
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2answers
11k views

Minimum number of processes for the deadlock?

A system has 6 identical resources and $N$ processes competing for them. Each process can request at most two requests. Which one of the following values of $N$ could lead to a deadlock? 1 ...
6
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1answer
606 views

Bounded waiting and starvation free in critical section problem

i have 4 question regarding relation between starvation and bounded waiting. 1.Does starvation-freedom imply deadlock-freedom? My Answer-: From here, definition of starvation free is Freedom ...
6
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1answer
546 views

Is this solution to the dining philosopher's problem entirely valid?

In a question on Stack Overflow, the answer by Patrick Trentin lists the following solution to the dining philosopher's problem: A possible approach for avoiding deadlock without incurring ...
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3answers
1k views

When do deadlocks occur?

I was reading about deadlocks in Operating Systems. Where I came across two examples below. Circles with label $P_x$ are processes. Squares with label $R_x$ are resources. Each dot in the square ...
5
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2answers
130 views

For a given certain situation how to prove that the system will never get into the state of Deadlock

The situation is as follows 'm' process shares 'n' resources of same type. The maximum need of each process does not exceed 'n' and the sum all their maximum needs is always less than m+n. In ...
4
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2answers
487 views

How probable is a deadlock in the dining philosophers problem

I created this simulation of the dining philosophers problem, but did not manage to initialize it with four philosophers without running into a deadlock: *Philosophers are represented by black ...
4
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6answers
2k views

Does Deadlock imply Starvation

If there is a deadlock between the processes does that mean that there is starvation also? My Thinking: deadlock is no process using that resources , but starvation is like not giving chance to only ...
4
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1answer
88 views

How does lack of deadlock relate to computability in process calculi?

I'm interested in knowing things about the computability of concurrent programs. If you had a Turing complete language that also let you branch off new programs but had no means of communication ...
4
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1answer
1k views

What is the difference between “deadlock prevention” and “deadlock avoidance”

I have studied about both of these on many places like this, this and this, but still it is not that much clear that what the actual difference is between these two. The Wikipedia links (first and ...
4
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1answer
1k views

How do locks work?

Suppose I have an application with two threads, which both use the same resource. Normally, a synchronized block keeps these threads from messing with the resource in a way the user doesn't expect. I ...
4
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1answer
126 views

Does a reentrant list for signal queue in a single-thread environment exist?

I need to handle Unix signals in a single-threaded application with the following goals: Signals doesn't mask on receive (thus, the signal handler must be reentrant). I am not allowed to lose signal ...
3
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1answer
2k views

How to satisfy bounded waiting in case of deadlock?

I have a doubt regarding bounded waiting. Deadlock implies no Progress because the processes take indefinite time to decide who will enter the critical section . But, Does deadlock implies no ...
3
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1answer
672 views

Why deadlock in cigarette smokers problem

"The Little Book of Semaphores" (2nd Ed. by Allen B. Downey, section 4.5.1) as well as Wiki (link) mentioned that a trivial solution (as shown below) to the 'Cigarette smokers problem' will cause a ...
3
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1answer
2k views

Provide some help regarding the “Dining Philosophers Problem”?

I have an assignment based on operating systems and the question is divided into two sub-questions. The first is: Prove any seating arrangement of lefties and righties, with at least one of each ...
3
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1answer
704 views

A real life system that faces and solves the dining philosophers problem

I'm looking for an application of the dining philosophers problem. Is there some real life system that faces the concurrency problem of "the dining philosophers problem" and implements a solution? I'...
3
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2answers
3k views

Falsifying the “Circular Wait” Condition - Deadlock Prevention

In the Circular Wait condition for Deadlock Prevention section of this, it is described as follows: One way to ensure that this condition never holds is to ...
3
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0answers
329 views

Lamport's Bakery algorithm with other > relation

i'm reading an old exam and one question was: Which property of the Bakery algorithm is violated with the following change? ...
3
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1answer
326 views

How do modern Operating Systems detect process starvation?

So first off do the modern operating systems like windows and linux have a method for detecting starvation? if not, why? and if they do, then how are they going to detect starvation of a process? (...
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2answers
6k views

Bankers Algorithm-Is the system in safe state?

Could somebody please provide a step-through approach to solving the following problem using the Banker's Algorithm? A system contains 10 units of resource class Ru. The resource requirements of ...
2
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1answer
116 views

Deadlock prevention by killing a victim

In our operating systems class, the teacher told us about deadlocks prevention methods. One of them is that to select as a victim the process which requires the CPU time or one that requires a lot of ...
2
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1answer
660 views

When will deadlock occur in this producer-consumer code

I was reading about Producer Consumer problem from Operating Systems by William Stallings where following code was given: ...
2
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1answer
49 views

Designing solution to critical section problem with two semaphores vs single semaphore

I came across following problem: Let two processes P1 and P2 are there: ...
2
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1answer
2k views

Confusion in Banker's Algorithm: How resources are allocated?

I have seen examples about Banker's Algorithm from this Wikipedia link, this book and many other places. In all these examples some processes are allocated ...
2
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1answer
123 views

Deadlock avoidance: How does the system know in advance about the number of resources required by a process?

While studying about Deadlock Avoidance I came across a paragraph which states as given below: When the system needs to issue any resource to any process, then ...
2
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1answer
344 views

Disabeling interrupts to solve critical section issue on multiprocessor system

Assume I have a multicore system and a critical section. I understand how disableling interrupts on a single core systems solves the critical section problem. So assume I could disable interrupts on ...
2
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0answers
21 views

Does this state certify to be called as a deadlock?

I came across following problem: Barrier is a synchronization construct where a set of processes synchronizes globally i.e., each process in the set arrives at the barrier and waits for all others ...
2
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0answers
98 views

Deadlock vs “Progress” requirement of the solution to the critical section problem

I came across following problem: Consider following code: ...
2
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0answers
304 views

Given a program which when executed spawns two concurrent processes : semaphore X : = 0 ; Is it possible for process P1 and P2 to starve?

Given below is a program which when executed spawns two concurrent processes: ...
2
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1answer
324 views

Does starvation freedom imply progress?

The above answer taken from the book https://www.amazon.com/Operating-Systems-Sibsankar-Haldar/dp/8131730220 says starvation freedom may not imply progress as processes can be deadlocked. I think ...
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1answer
366 views

Deadlock Solutions: Lock Ordering

This is from a textbook on operating systems. This is not homework, just part of the chapter on deadlocks. ...
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3answers
7k views

Deadlock and cycle in a resource allocation graph

Here is a resource allocation graph asked in my Operating Systems Theory midterm. The question is, "Is there a deadlock here? Explain your answer in detail" Ra and Rb are resource sets and every dot ...
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1answer
555 views

Is bounded waiting satisfied in the 2 Process Solution?

Suppose, There are $2$ processes $P1$ and $P2$. It is given that Mutual Exclusion and Progress are satisfied by these $2$ processes. Suppose, Programming protocol is designed such that CPU only ...
1
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1answer
159 views

Does the following modified Two-Phase Locking protocol ensure serializability and freedom from deadlock?

Consider the following variant of the two phase locking protocol. Suppose a transaction $T$ accesses (for read or write operations), a certain set of objects ${O_1,...,O_k}$. The modified algorithm ...
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2answers
2k views

Help interpreting this deadlock question

I have this assignment question but I am a bit unsure how to go about answering it. The question is as follows and accompanied by the image below: Three processes are competing for six resources ...
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1answer
1k views

Bankers algorithm - How does it work?

I'm currently studying deadlocks and I'm trying to learn myself the bankers algorithm. In this example my teacher goes to B first, then C and finally A. He adds (I think) 2 (row b, Has) with 3 (...
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1answer
99 views

How can I solve this deadlock related problem mathematically?

I came across following problem: A system has n resources R0,…,Rn-1,and k processes P0,….Pk-1.The implementation of the resource request logic of each process Pi is as follows: ...
1
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1answer
88 views

Can 2-philosophers problem be analogous to dining philosophers problem?

Two philosophers A and B, two forks numbered "1", "2"; A needs both "1" and "2" for eating, so does B. Is this theoretical a dining philosopher problem? I'm questioning about the forks philosopher A ...
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1answer
400 views

Can a safe state in Banker's Algorithm cause deadlock eventually?

I know that unsafe state does not always mean deadlock. That is a situation that banker's algorithm does not detect deadlock accurately. I am just wondering if there is any example of a safe state ...
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1answer
39 views

deadlock caused by a cyle of locks ? unprobable event causing it or just a false intuition

Thanks a lot for your help. I want to understand what really causes what I suppose to be a deadlock: I have standards objects, let's call it 'Words' that contains 3 letters and a key; (it doesn t ...
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0answers
47 views

How to prove that an algorithm has no deadlock

I need to mathematically prove that this algorithm is deadlock-free: ...
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0answers
22 views

Comparing wait-signal alternatives for synchronizing two piece of programs

I came across following problem: A certain computation generates two arrays a and b such that ...
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1answer
99 views

What fraction of all combinations is guaranteed to be deadlock free?

I found this question in the exercise of Tanenbaum (operating systems): Two processes, $A$ and $B$,each need three records $1, 2, \text{ and } 3$ in a database. If $A$ asks for them in the order $...
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0answers
37 views
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0answers
49 views

Is a single starved process considered deadlocked?

In regard to the critical section problem, an algorithm that switches between allowing one of two processes, P1 or P2, to complete their critical section would cause starvation for P1 if P2 stayed in ...
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0answers
113 views

two phase locking and a contest question?

In 2PL (two phase locking), what advantage(s) does the rigorous model have over the strict model? I) There is no advantage over the strict model. II) In contrast to the strict model, it ...
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0answers
200 views

Solve a basic mutex lock problem while preventing deadlock

I am solving a problem with a bridge, where you have a one way bridge with people coming from each side. To solve this problem while preventing deadlock (two people going opposite directions on the ...
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2answers
1k views

difference between deadlock avoidance and detection

I know the difference between deadlock prevention and avoidance. But i want to know the difference between deadlock avoidance and detection. ?
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1answer
68 views

What happens if the holder of a lock tries to acquire a lock? [closed]

In a system, suppose there is a process and a resource with only one instance. Let us assume that the process holds the instance and requests the same instance of that resource. Will there be a ...