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hey guys! I need to know how to use pthreads with mutex to protect the critical section!!

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asked how to protect a critical section with pthreads; linked a tutorial that is useful background. The basic pthreads pattern is: initialize a pthread_mutex_t, call pthread_mutex_lock(&m) before the critical section, and pthread_mutex_unlock(&m) after. Always check return values and guarantee the mutex is released on every path (use a cleanup/goto pattern or an RAII wrapper in C++). Avoid holding a mutex across long I/O or blocking calls. See the POSIX reference for the lock/unlock semantics: pthread_mutex_lock(3).

A minimal C pattern:

static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

void *thread_fn(void *arg) {
    pthread_mutex_lock(&lock);
    /* critical section */
    pthread_mutex_unlock(&lock);
    return NULL;
}

On implementing monitors with semaphores: it is possible but error-prone. A common Mesa-style approach uses a binary semaphore as the monitor lock and, for each condition, a counting semaphore plus an integer waiter count. Wait does: increment waiter count, release monitor lock, wait on condition semaphore, re-acquire lock. Signal does: if waiter count > 0 then post the condition semaphore. That yields Mesa semantics; true Hoare-style handoff requires extra bookkeeping. Prefer pthread_cond_t + pthread_mutex_t for clarity and correctness—see pthread_cond_wait(3) and POSIX semaphores for primitives: sem_init(3).

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Member Avatar for sree_ec

hey guys! I need to know how to use pthreads with mutex to protect the critical section!!

read this

Member Avatar for aplh_ucsc

Thankx, that is just what i want.
can u explain how to implement monitors using semaphores!

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