pthread gets cancelled before releasing locks

 In multithreaded programming using pthreads in C/C++, it's essential to handle thread cancellation correctly, especially when locks are involved. When a thread is canceled before releasing locks, it can lead to resource leaks and potential deadlocks. To avoid this issue, you should follow some best practices:

1. **Use Cancellation Points**: Ensure that your code has well-defined cancellation points where a thread can be safely canceled. These points are locations in your code where it's safe to terminate a thread, such as after releasing locks.

2. **Explicitly Release Locks**: Always explicitly release locks (mutexes) before a thread is canceled. You can use `pthread_mutex_unlock` to release a mutex. Failing to release a lock can lead to deadlock scenarios, where other threads may be unable to acquire the locked resource.

3. **Cancellation Cleanup Handlers**: Consider using cancellation cleanup handlers (`pthread_cleanup_push` and `pthread_cleanup_pop`) to ensure that resources like locks are released even when a thread is canceled. Cleanup handlers are executed when a thread is canceled, allowing you to release locks and other resources gracefully.

Here's an example of using cleanup handlers to release a lock when a thread is canceled:

```c

#include <pthread.h>

// Mutex variable

pthread_mutex_t myMutex = PTHREAD_MUTEX_INITIALIZER;

// Thread function

void* myThreadFunction(void* arg) {

    pthread_cleanup_push(cleanupHandler, NULL);

    // Lock the mutex

    pthread_mutex_lock(&myMutex);

    // ... Critical section

    pthread_cleanup_pop(1); // Run cleanup handler

    // Continue thread execution

    // Release the lock when done

    pthread_mutex_unlock(&myMutex);

    return NULL;

}

void cleanupHandler(void* arg) {

    // Ensure the lock is released if the thread is canceled

    pthread_mutex_unlock(&myMutex);

}

```

By using cleanup handlers, you ensure that even if the thread is canceled prematurely, the lock is released, preventing potential deadlocks and resource leaks. This approach helps you handle thread cancellation gracefully in the presence of locks.