Memory leaks and seg faults when using OpenMP and OpenSSL

Question

I have a huge code (its my school project) where I use Openssl. Everything was working perfeclty, util I decided I will go multithreaded. I chose openmp

Answer 1

Take a look at the example openssl/crypto/threads/mttest.c in the OpenSSL source code tree. Basically, you have to provide two callback functions:

• one that implements locking and unlocking and
• one that returns a unique thread ID.

Both are easily implemented using OpenMP:

omp_lock_t *locks;

// Locking callback
void openmp_locking_callback(int mode, int type, char *file, int line)
{
  if (mode & CRYPTO_LOCK)
  {
    omp_set_lock(&locks[type]);
  }
  else
  {
    omp_unset_lock(&locks[type]);
  }
}

// Thread ID callback
unsigned long openmp_thread_id(void)
{
  return (unsigned long)omp_get_thread_num();
}

Before you start, the locks have to be initialised and callbacks set:

void openmp_thread_setup(void)
{
  int i;

  locks = OPENSSL_malloc(CRYPTO_num_locks() * sizeof(omp_lock_t));
  for (i=0; i

You should call openmp_thread_setup() once in your program somewhere before the first parallel region and you should call openmp_thread_cleanup() once after the last parallel region:

// Program start

openmp_thread_setup();

#pragma omp parallel
{
   // Parallel OpenSSL calls are now data race free
}

#pragma omp parallel
{
   // Parallel OpenSSL calls are now data race free
}

#pragma omp parallel
{
   // Parallel OpenSSL calls are now data race free
}

openmp_thread_cleanup();

// Program should end now