Resource acquisition and pthreads

Question

I'm acquiring some resources in increasing order. Which version is better? I was told that #2 leads to starvation of threads wanting higher numbered resources. Is this true? If so, how and why?

a[] sorted array 

1.

for(int i = 1; i < N; ++i) {
  lock(mutex)
  while(!resource_available[a[i]]) {
    pthread_cond_wait(&cond_w[a[i]], &mutex);
  }
  resource_available[a[i]] = 0;
  unlock(mutex)
}

2.

lock(mutex)
for(int i = 1; i < N; ++i) {
  while(!resource_available[a[i]]) {
    pthread_cond_wait(&cond_w[a[i]], &mutex);
  }
  resource_available[a[i]] = 0;
}
unlock(mutex)

EDIT: It turns out that order in which you release resources makes the difference, not above constructs. If you release them in order you received them starvation happens, if in opposite then probably not.

Answer 1

Both are going to be virtually equivalent, since in example 1 the thread will almost always reacquire the mutex without sleeping immediately after unlocking it, since there's only two expressions evaluated in between.