Fix OpenSSL <1.1.0 threads setup. (#111)

* Fix OpenSSL <1.1.0 threads setup.

OpenSSL 1.0.2 and older require expicit locking callbacks in order to be
thread safe. Without this fix, using TLS and multiple threads on older
versions of OpenSSL would result with crashes/unexpected behavior.

Author: yossigo

memtier_benchmark.cpp

@@ -1138,6 +1138,55 @@ run_stats run_benchmark(int run_id, benchmark_config* cfg, object_generator* obj
 }
 
 #ifdef USE_TLS
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
+static pthread_mutex_t *__openssl_locks;
+
+static void __openssl_locking_callback(int mode, int type, const char *file, int line)
+{
+    if (mode & CRYPTO_LOCK) {
+        pthread_mutex_lock(&(__openssl_locks[type]));
+    } else {
+        pthread_mutex_unlock(&(__openssl_locks[type]));
+    }
+}
+
+static unsigned long __openssl_thread_id(void)
+{
+    unsigned long id;
+
+    id = (unsigned long) pthread_self();
+    return id;
+}
+#pragma GCC diagnostic pop
+
+static void init_openssl_threads(void)
+{
+    int i;
+
+    __openssl_locks = (pthread_mutex_t *) malloc(CRYPTO_num_locks() * sizeof(pthread_mutex_t));
+    assert(__openssl_locks != NULL);
+
+    for (i = 0; i < CRYPTO_num_locks(); i++) {
+        pthread_mutex_init(&(__openssl_locks[i]), NULL);
+    }
+
+    CRYPTO_set_id_callback(__openssl_thread_id);
+    CRYPTO_set_locking_callback(__openssl_locking_callback);
+}
+
+static void cleanup_openssl_threads(void)
+{
+    int i;
+
+    CRYPTO_set_locking_callback(NULL);
+    for (i = 0; i < CRYPTO_num_locks(); i++) {
+        pthread_mutex_destroy(&(__openssl_locks[i]));
+    }
+    OPENSSL_free(__openssl_locks);
+}
+
 static void init_openssl(void)
 {
     SSL_library_init();
@@ -1146,7 +1195,15 @@ static void init_openssl(void)
         fprintf(stderr, "Failed to initialize OpenSSL random entropy.\n");
         exit(1);
     }
+
+    init_openssl_threads();
 }
+
+static void cleanup_openssl(void)
+{
+    cleanup_openssl_threads();
+}
+
 #endif
 
 int main(int argc, char *argv[])
@@ -1526,5 +1583,7 @@ int main(int argc, char *argv[])
         SSL_CTX_free(cfg.openssl_ctx);
         cfg.openssl_ctx = NULL;
     }
+
+    cleanup_openssl();
 #endif
 }