Issue with OpenSSL in multithreaded environment

[Staneva, Yana]

Help please.

I have a Win32 application (service) that loads several dlls that make OpenSSL 
calls. Also there is a separate dll that takes care of the OpenSSL 
initialization (thread setup, SSL_library_init(), SSL_CTX_new() ).
I've followed the samples online on how to do the thread setup, so I have the 
following:

#define  MUTEX_TYPE        HANDLE

#define  MUTEX_SETUP(x)    (x) = CreateMutex( NULL, FALSE, NULL )
#define  MUTEX_CLEANUP(x)  CloseHandle(x)
#define  MUTEX_LOCK(x)     WaitForSingleObject( (x), INFINITE )
#define  MUTEX_UNLOCK(x)   ReleaseMutex(x)
#define  THREAD_ID         GetCurrentThreadId()

// This array will store all of the mutexes available to OpenSSL.
static MUTEX_TYPE*   mutex_buf = NULL;

static unsigned long id_function()
{
   return ((unsigned long)THREAD_ID);
}

static void locking_function(int mode, int n, const char* file, int line)
{
   if ( mode & CRYPTO_LOCK )
      MUTEX_LOCK( mutex_buf[n] );
   else
      MUTEX_UNLOCK( mutex_buf[n] );
}

int THREAD_setup()
{
   mutex_buf = (MUTEX_TYPE*)malloc( CRYPTO_num_locks() * sizeof(MUTEX_TYPE) );
   if ( !mutex_buf )
      return 0;

   for(int i=0; i<CRYPTO_num_locks(); ++i)
      MUTEX_SETUP( mutex_buf[i] );

   // id_function(void) is a function that returns a thread ID. It is not 
needed on Windows?
   CRYPTO_set_id_callback( id_function );
   CRYPTO_set_locking_callback( locking_function );

   return 1;
}

int THREAD_cleanup()
{
   if ( !mutex_buf )
      return 0;

   CRYPTO_set_id_callback( NULL );
   CRYPTO_set_locking_callback( NULL );

   for(int i=0; i<CRYPTO_num_locks(); ++i)
      MUTEX_CLEANUP( mutex_buf[i] );

   free( mutex_buf );
   mutex_buf = NULL;

   return 1;
}

Also the logic makes sure that there is only one SSL_CTX object for the process.

What happens is that when a second thread tries to access the OpenSSL the 
system crashes in:

static unsigned long WINAPI _threadstart (void * ptd)

Can somebody please help me identify the problem?
Yana