Exploring Threads in Linux for Concurrent Execution and Multitasking

Overview

Threads in Linux are pivotal in enabling concurrent execution and multitasking within processes. Unlike traditional processes, which have their own address space and resources, threads share the same memory space and resources within a process, allowing for lightweight and efficient multitasking.

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Introduction

Threads are crucial parts of contemporary computing systems for programs to run numerous tasks simultaneously and make optimum use of system resources. Linux threads share the same memory and resources as processes since they are implemented as lightweight execution units within them.

In this blog post, we will examine the creation, administration, synchronization, and use cases of threads in Linux to highlight their advantages and uses.

Understanding Threads

Under Linux, the POSIX threads (pthreads) API creates threads inside processes. It offers a standardized interface for creating, synchronizing, and communicating threads. This allows for effective communication and data exchange across threads within a process because they share the same address space, file descriptors, and other process-related resources.

Creation of Threads

Threads are small execution units that utilize the same memory and resources as the rest of the process. Because threads within a process can communicate directly, they can execute tasks concurrently and efficiently using resources, unlike processes with their own memory and resources.

Example: Creating Threads in Linux

Let us use a basic example to show how to create threads in Linux:

#include <stdio.h>
#include <pthread.h>
 // Thread function
void *thread_function(void *arg) {
    printf("Hello from thread!\n");
    return NULL;
}
 int main() {
    pthread_t tid;
    pthread_create(&tid, NULL, thread_function, NULL);
    pthread_join(tid, NULL); // Wait for the thread to finish
    printf("Thread execution complete\n");
    return 0;
}

#include <stdio.h>

#include <pthread.h>

// Thread function

void *thread_function(void *arg) {

printf("Hello from thread!\n");

return NULL;

}

int main() {

pthread_t tid;

pthread_create(&tid, NULL, thread_function, NULL);

pthread_join(tid, NULL); // Wait for the thread to finish

printf("Thread execution complete\n");

return 0;

}

thread

In this example, we define the thread function() as the thread start function and use pthread_create() to create a new thread. The pthread_join() method is utilized to pause the execution of a thread before continuing.

Thread Synchronization

To prevent data races and provide appropriate coordination, threads operating within a process frequently need to synchronize their execution. Linux has thread synchronization and communication primitives such as semaphores, mutexes, and condition variables.

Example: Thread synchronization with mutex

Let’s see how to safeguard shared resources with thread synchronization and a mutex:

#include <stdio.h>
#include <pthread.h>
 pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
int shared_counter = 0;
 / Thread function
void *thread_function(void *arg) {
    pthread_mutex_lock(&mutex);
    shared_counter++;
    printf("Thread: Incremented counter to %d\n", shared_counter);
    pthread_mutex_unlock(&mutex);
    return NULL;
}
 int main() {
    pthread_t tid[5];
    // Create multiple threads
    for (int i = 0; i < 5; i++) {
        pthread_create(&tid[i], NULL, thread_function, NULL);
    }
    // Wait for all threads to finish
    for (int i = 0; i < 5; i++) {
        pthread_join(tid[i], NULL);
    }
    printf("All threads finished execution\n");
    return 0;
}

#include <stdio.h>

#include <pthread.h>

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

int shared_counter = 0;

/ Thread function

void *thread_function(void *arg) {

pthread_mutex_lock(&mutex);

shared_counter++;

printf("Thread: Incremented counter to %d\n", shared_counter);

pthread_mutex_unlock(&mutex);

return NULL;

}

int main() {

pthread_t tid[5];

// Create multiple threads

for (int i = 0; i < 5; i++) {

pthread_create(&tid[i], NULL, thread_function, NULL);

}

// Wait for all threads to finish

for (int i = 0; i < 5; i++) {

pthread_join(tid[i], NULL);

}

printf("All threads finished execution\n");

return 0;

}

thread2

In this example, a mutex-protected critical area has a shared counter incremented by many threads. This prevents data corruption because only one thread can access the shared resource at a time.

Thread Attributes

Using thread attributes, you can adjust thread features like priority, scheduling policy, and stack size. Before thread formation, particular attributes can be specified using the pthread_attr_set*() functions. The pthread_attr_init() function initializes a thread attribute object.

Thread Cancellation

Linux offers the pthread_cancel() function as a means of canceling threads. By using the pthread_setcancelstate() and pthread_setcanceltype() functions to set the cancellation state and type properties, threads can respond to cancellation requests.

Thread Safety in Library Functions

It’s crucial to make sure that library functions utilized by threads are thread-safe while developing multithreaded Linux systems. The correct behavior of library functions when called concurrently by several threads is ensured by thread safety. Most Linux standard library functions are thread-safe; however, programmers should exercise caution when creating their own or utilizing third-party libraries.

Conclusion

Linux threads are essential for concurrent execution and effective resource use within processes. Through comprehension of their generation, administration, synchronization, and real-world applications, programmers can utilize threads to construct scalable and responsive software systems. Linux offers a strong foundation for creating multithreaded applications in various areas, from enterprise servers to embedded devices, with strong support for thread creation, synchronization primitives, and thread characteristics.

Drop a query if you have any questions regarding Linux threads and we will get back to you quickly.

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FAQs

1. What are Threads in Linux?

ANS: – Under Linux, threads are small, shared memory and resource-sharing execution units within processes. They make it possible for a process to multitask and execute concurrently.

2. How do Linux threads get created?

ANS: – The pthread_create() function in Linux is used to create threads. It accepts the following arguments: a pointer to a pthread_t object representing the thread identifier, thread attributes, a pointer to the thread start function, and optional arguments to provide to the thread object.

3. What are the advantages of using threads in Linux?

ANS: – Threads in Linux allow for concurrent execution of tasks, improving system efficiency and responsiveness. They enable parallelism, efficient resource utilization, and seamless multitasking within processes.

WRITTEN BY Vaishali Bhawsar

Vaishali is working as a Research Associate in CloudThat Technologies. She has good knowledge of Networking, Linux systems & C language, and currently working on various AWS projects along with, Terraform, Docker, and Ansible. She enjoys painting and cooking during her free time.