4,821 questions
0
votes
0
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103
views
Is this protection method multithread safe?
I've written a MQTT client for embedded system with RTOS (understand not POSIX, generally FreeRTOS). There's no pthread in the system. There's only 32 bits atomic instructions supported.
The client ...
- 3,682
-3
votes
0
answers
82
views
pthread_mutex_destroy fails with EBUSY: mutex has __count=1 but __lock=0 and __owner=0 [closed]
When attempting to destroy a mutex lock, the system encountered an inconsistent state: the lock was not held by any thread (indicated by __lock = 0and __owner = 0), but its internal reference count (...
-4
votes
1
answer
94
views
A global sync.Mutex don't work with multiple client packages?
I have a package "tools" that expose a method that must execute some logic only one time. The next calls don't do nothing.
The file tools/tools.go is like:
package tools
import (
"...
1
vote
0
answers
31
views
Why use a delay time less than portMAX_DELAY when waiting for a semaphore/mutex/queue FreeRTOS?
First I want to make sure I'm understanding the behavior of what is happening when trying (and failing) to take a semaphore or mutex...
When this code runs (assuming xSemaphoreTake is going to fail to ...
- 1
3
votes
2
answers
149
views
c++ mutex with different data in the critical section
class MyTest {
void getter() {
std::unique_lock lock(mutex_);
if (!set_) {
cout << "set already" << endl;
}
lock.unlock();
// question ...
- 313
3
votes
1
answer
147
views
Copying heap allocated memory in multiple threads... Is a mutex required or is it safe?
Environment is Ubuntu 24.04, QT Creator 6, g++ 13.3, pthreads.
Given the following code (error handling has been removed for readability):
#include <iostream>
#include <thread>
#include &...
- 631
4
votes
1
answer
143
views
c++ mutex and memory barrier
class MyTest {
void getter() {
std::unique_lock lock(mutex);
if (!set_) {
cout << "set already" << endl;
...
- 313
6
votes
2
answers
180
views
C++ pointers and concurrency
I need some help for understanding general basics of shared resource access in C++ multithreading.
When I need some variable that must be accessible for several threads, I declare it as atomic, or ...
3
votes
1
answer
83
views
munmap shared memory with locked robust mutex makes it deadlock, why?
I need to use robust mutexes for IPC in case one of my processes crashes while holding a mutex locked. Definition is clear from e.g. man pthread_mutexattr_setrobust and I will not repeat it here.
I ...
- 600
2
votes
0
answers
48
views
Python (with Kivy) app using buildozer crashes on Android 14/15 with pthread_mutex_lock called on a destroyed mutex in SDLActivity
Title
Android 14/15 crash with Kivy + Buildozer: pthread_mutex_lock called on a destroyed mutex (SDLActivity)
Problem Description
I'm building a Python game using Kivy, packaged for Android via ...
- 21
1
vote
0
answers
274
views
Python mutex.cc lock issue
I have a python program that hangs in a library call on this message:
[mutex.cc : 452] RAW: Lock blocking 0x6000009e1158 @
I started the program with trace to see what is going on, and I get (a lot ...
- 4,483
0
votes
2
answers
335
views
Sleeping Barber problem: how to prevent the barber from cutting before the customer is ready?
Recently, I've been studying the classic Sleeping Barber problem and came across a possible solution from Wikipedia:
# The first two are mutexes (only 0 or 1 possible)
Semaphore barberReady = 0
...
- 60
2
votes
0
answers
190
views
How to implement unique_lock for multiple mutexes
<mutex> contains different RAII wrappers:
lock_guard - single mutex, always locked
unique_lock - single mutex, can defer or try
scoped_lock - many mutexes, always locked, supersedes lock_guard ...
- 3,097
2
votes
1
answer
112
views
Strange behaviour of atomicCAS when used as a mutex
I'm trying to learn CUDA programming, and recently I have been working on the lectures in this course: https://people.maths.ox.ac.uk/~gilesm/cuda/lecs/lec3.pdf, where they discussed the atomicCAS ...
- 710
1
vote
2
answers
100
views
Sequence of Events in : mutex.unlock() vs returning from a function
short brief - I want to understand the sequence of event when returning from a function and unlocking a mutex in the same function.
helper macro: to print to screen
#define TRACE() {std::cout <&...
- 53