Questions tagged [threads]

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Can User Level Thread read/write Kernel thread?

As far as I read in a OS text book (Operating Systems by Silberschatz) Kernel mode is for privileged task, so it it true to claim that "User Level Thread can read/write Kernel threads" ? ...
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Does every thread have its main function?

Does every thread have its own main function? I know that its have its own stack, but what about main function (not necessarily a function which called main). For example, when creating a thread, we ...
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What are the differences between Earliest Deadline First (EDF) and Earliest Due Date (EDD)?

From my understanding, the EDF (Earliest Deadline First) rule is essentially an iterative "version" of the EDD (Earliest Due Date) rule, which allows for preemption. At every point in time, ...
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How to trigger a thread to start working using semaphore?

How to trigger a thread to start working using semaphore? I have find a lot of explanation about thread and semaphore but i still don't understand, any help please
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Thread - contention vs race

The terms contention and race are used interchangeably when it comes to thread's state(at critical section). Are they same?
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parallelized data structure

I'm searching a data structure that supports O(1) concurrent insertions (thread number is known in advance) and iteration over its elements (insertion order doesn't need to be preserved). While one ...
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20 views

Preemptive priority scheduling problem with same priority

So if T1(priority 3, arrived first) was preempted it is put back to the runqueue. If there is already T4(priority 3, arrived fourth) inside the runqueue, which one of these two will be handled first?! ...
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119 views

Why the most dominant programming languages didn't follow CSP thread model?

I was trying to ask this question in StackOverflow, but later realized that this question is more relevant to general computer science, not specific engineering problems. If you think it's not, please ...
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1answer
34 views

How does a dual core microprocessors run so many programs?

I have a laptop with Intel dual core and it runs, the OS windows, and many application from Opera, age of empires, word, excel etc open at once just fine. If it only has 2 cores, how can so many ...
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In multithreaded computations, how does parallelism, slackness and speedup affect the running time?

In the CLRS book it mentions that during some world-class multithreaded chess-playing program, developers had to prototype their program on a 32-processor computer then run it on a supercomputer with ...
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41 views

Can many threads run in a parallel in many-to-one model?

The book I am reading suggests that in a many-to-one multi-threading model, the threads are unable to run in parallel in a multi-core system. I am thinking this is not the case because if we have many-...
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1answer
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Does this lock have a name (related to reader-writer lock)

The object can be locked two different ways, where if the lock is entered the same way a second time, the lock is recursive, but if it's entered the other way, it blocks. Like a reader-writer lock, ...
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What does it mean by “consistent view of memory” in lock-free dequeue implementation?

I am currently reading this paper by Chales-Lev. This paper explain an implementation of work-stealing dequeue. The part where I don't understand is in the implementation of steal operation. ...
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23 views

Parallel Thread Processing Variable Question

if there is a better stack exchange suited for this question please inform me. say you have a thread that is constantly checking the state of a variable in 2 ms intervals ...
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1answer
16 views

multithreading - duration of jobs

" How long will it take for 2 jobs to complete if they're running in parallel, knowing that both have a total of 20 minutes of CPU usage time and 50% IO" I calculated the CPU usage: ...
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1answer
37 views

Threads and Operating System

In a computer, the processor executes different threads and changes between them, the operating system is a program at the end that it´s being executed by the processor, there exists the posibility ...
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1answer
182 views

What should be the minimum value when the two threads are executed concurrently

int count=0; void *thfunc() { int ctr=0; for(ctr=0;ctr<100;ctr++) count++; } If *thfunc() is executed by two threads concurrently in a uniprocessor ...
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162 views

Why are threads called the unit of dispatch?

Threads called the "unit of dispatch" but what does that mean? I was looking over the web and two operating systems books but I can't find the answer. It seems that processes are defined by two ...
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1answer
1k views

About hardware multithreading

I'm reading Multithreading (computer architecture) - Wiki, aka hardware threading, and I'm trying to understand the second paragraph: (p2): Where multiprocessing systems include multiple complete ...
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How is switching among user-level threads realised in the user space?

This is with respect to user-level threads where the kernel only knows about the process as a whole, and threads are created and maintained in the user space. Each thread has its PC, registers, stack ...
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1answer
56 views

Reason for thread pooling

Can someone explain what is the reason for thread-pooling in Linux, even if the threads are light to create and destroy??
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Definition of PrefixSum function

I came across this paper and attempting to go through the implementation of randomized selection algorithm on page 8. Step 1 of the algorithm suggest to compute $s = PrefixSum(n_i, p)$. Where $p$ is ...
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User-level threads and information available to the kernel

User-level threads are transparent to the kernel. How is htop able to show user-level threads running on my system? I know that those threads are user-level threads ...
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1answer
36 views

Can Multiprocessor Systems Implement Both Temporal Multithreading and Simultaneous Multithreading?

I am aware that multiprocessor systems often implement simultaneous multithreading in order to allow multiple threads to run on different CPUs. I am also aware that uni-core systems often implement ...
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1answer
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What is the Difference Between Many-to-Many (M:M) Threading and Hybrid (M:N) Threading?

I have been researching threading and come across several websites which all say contradicting statements about which and how many thread models exist. Some websites say there are only three: 1:1, M:1 ...
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38 views

semaphore for two groups of processes

Can someone help me giving a pseudo code to this problem : There are two groups of processes , A and B. Maximum 3 Processes from group A or group B(only from one group) can use the given resource . ...
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1answer
120 views

What is the benefit of using one to one thread mapping model instead of Many to Many or two level?

So in the silberschatz O.S book it says Windows uses one to one model (mapping user level threads to kernel level threads) but why? i thought many to many and two level models are much better, ...
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1answer
66 views

Why is there no one to many Multithreading Model?

I am studying various multi-threading models. Here the user threads are mapped to Kernel Threads. They are - ...
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2answers
112 views

What is the difference between a page and thread?

"Each process that is executed is divided into blocks of same size, called pages." "Thread is a part of process being executed." Are pages and threads both part(s) of process? Whats the difference ...
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1answer
144 views

Work-stealing: where and how many to steal

If one ignores the conflicts when accessing the dequeue in Work-Stealing algorithms, does it matter (and in what ways) if one steals from the top or bottom (or anywhere randomly) of the dequeue? Does ...
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1answer
23 views

Need to understand signals received vs sent

What is meant by in the following statement (from the paper titled "Implementing Lightweight Threads"): As in singlethreaded processes, the number of signals received by the process is less than ...
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1answer
183 views

Hardware thread context and register renaming

I'm having some issues understanding what happens on a context switch with the physical register file in an out-of-order CPU that implements context switching. Suppose that a CPU consists of 4 ...
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1answer
3k views

What is “time-slice multi-threading”?

My goal is to understand the exact differences between SoEMT, SMT and "time-slice multi threading". Thus far I already found information on SoEMT and SMT and it does not seem to hard to find more on ...
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1answer
158 views

Multi-threading : N cores = N times one core?

This question is about modern CPU architectures and multi-threading. I'm mainly interested in personal computers or servers having 2, 4, 8, 16... cores like for example an Intel core i7. I mean not a ...
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53 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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1answer
453 views

Understanding google's user level threads in kernel threads

I came across Paul Turner work on increasing efficiency of M:N threading model. I am not able to grasp the concept at slide 18 of LPC-User-Threading It says : for two threads ...
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149 views

Algorithm to construct timeline graph with arrival and departure times

So I am trying to construct a timeline graph for threads interacting with synchronization functions e.g. pthread_mutex_lock. I have the following information: 1- ...
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1answer
88 views

What do `i` and `Number` represent in the Bakery Algorithm?

I am studying the bakery algorithm, and I am unsure of what the variable i represents in it. I understand that Entering ...
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1answer
563 views

How can context switch affect the modification of a variable?

float myTotalAmount=0; void update(float amt){ myTotalAmount+= amt; } Task A called update(10); Calculated ...
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1answer
111 views

Is there a generic word for “thread or process”?

I'm writing about a problem that could be caused by race conditions between multiple threads, or OS-level processes on the same machine or different machines, or VM-level processes like the Erlang VM ...
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3answers
2k views

Why are most mutex implementations unfair?

My understanding is that most popular implementations of a mutex (e.g. std::mutex in C++) do not guarantee fairness -- that is, they do not guarantee that in instances of contention, the lock will be ...
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1answer
51 views

One rational interval function and one irrational, will they ever collide?

This question may be a little mathy or hardware-y, so I may have to ask elsewhere. I've recently learned that if a is a positive rational number and b is a positive irrational number, there exists no ...
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411 views

Do user level threads take advantage of multi processing?

I asked this question here on stackoverflow, but maybe because of off-topic over there, it didn't received proper response. Does user level threads take advantage of multiprocessing ? I read one such ...
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1answer
1k views

thread scheduling in multi core architecture

In multi core architecture, let us say we have M cores and N threads (N > M) and a process once assigned to a core can't migrate to another core's ready queue. We have to design scheduling policy to ...
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228 views

many to many multithreading

In many to many multithreading model the processor threads are multiplexed to a lesser or equal number of kernel threads. What exactly does it mean?? Does it mean that if a kernel is executing a ...
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2answers
6k views

How does RAM is shared in multi core environment?

I learnt that multi core processors have more than one processing units( i.e. the main executing units ALU etc.) and they are better at performance. I want to know how they share Physical memory. I'll ...
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1answer
159 views

Can threads use resources from other processes?

This is how I see threads. Please do correct me if I'm wrong: A thread is a part of a process that runs a sequence of program code. There can be many threads within a process that run different ...
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2answers
122 views

What does it mean that a core supports 2 threads?

I understand that a process may have multiple threads, and that a processor may have multiple cores to run processes in parallel. But I can't understand how a core may allow multiple threads, what ...
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1answer
154 views

What techniques could be used to support thread-local contexts and resources in a language?

I am interested in the subject of thread-local contexts, which is a feature that I use quite often in solutions, but seems to lack first-class support in any languages I have used. Quite often in ...