this is my code: there is a while loop in the wait function of a semaphore, can’t I use an if statement simply? Answer Because we can’t assume that after a thread is woken up and it requires the lock another thread has not already come along and taken the resource this is guarding:
Tag: semaphore
Strange POSIX semaphore behavior (stuck on sem_wait on Linux)
I’m trying to solve a school problem envolving POSIX semaphores. I’ve run into an issue that I’ve narrowed down to this simplified code: When compiling (using gcc -Wall -pthread sems.c -o sems) and running this program in Linux, I get the following output (the program doesn’t finish ex…
C system v Semaphore not locking critical region
I have a code that reads an integer from shared memory and then incerements the number in child processes. I’m using semaphore to lock this critical region so that the integer gets only increased if no other process is not increasing it. So I get a stable integer value. I have used SYSTEM V Semaphore fo…
Multithreading with Semaphor, Mutex and PThread
Me and a friend are currently working on basic multithreading examples for university in c. We’re supposed to solve the producer/consumer problem with a multithreaded buffer. We’ve got a working version using mutex and conditional variables, but trying to solve this using semaphores and mutex were…
How to find which process owns the named posix semaphore lock? [closed]
Closed. This question needs debugging details. It is not currently accepting answers. Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question. Closed 4 years ago. Improve this question I use…
what is “synchronising point” in multi threading?
I need to decide on how many counting semaphores needs to be used for one of the multi threaded application. I came to know, if we know synchronising points then we can decide the number of semaphores to be used. What are synchronising points? Answer A synchronization point is a place in the flow of execution…
Handling of blocked named semaphores after a system reboot
Within a Linux Box I’m using named semaphores to control access to system resources used by different processes. If the system accidentally crashes, it can happen, that a semaphore has been acquired but not given back yet. Given that situation, I noticed, that even after a reboot the semaphore remains s…
Semaphores and Mutex behaviour doubts
Do semaphores and mutexes synchronize both threads and processes, or only threads, or only processes? Edit: my mistake it’s C, not shell. Since I programmed through the shell I mistook it. And one more thing: are communication and synchronization the same? Answer SysV IPC semaphores synchronize between …
Working with semaphores and shared memory under Linux
I need to write a program that is creating a N amount of sub processes and every single one of them adds one to a shared memory variable. My idea is to use semaphores and shared memory, but the processes are not waiting for each other and the shared memory variable is also not working as I want it. mydefs.h
Waiting on multiple semaphores without busy-waiting (C/C++ Linux)
If I have more than one semaphore, how can I have a process block until at least one of the semaphores is free? I know I can do this with a busy-wait loop such as: But is there a way to do this without a busy-loop? Perhaps there’s some IPC technique other than semaphores that I should be using? Thanks