ensure that threading has been initialized in the first place before calling openblas_set_num_threads

driver/others/blas_server.c

@@ -850,6 +850,11 @@ void goto_set_num_threads(int num_threads) {
 
   long i;
 
+#ifdef SMP_SERVER
+  // Handle lazy re-init of the thread-pool after a POSIX fork
+  if (unlikely(blas_server_avail == 0)) blas_thread_init();
+#endif
+
   if (num_threads < 1) num_threads = blas_num_threads;
 
 #ifndef NO_AFFINITY

driver/others/blas_server_win32.c

@@ -478,7 +478,12 @@ int BLASFUNC(blas_thread_shutdown)(void){
 
 void goto_set_num_threads(int num_threads)
 {
-	 long i;
+	long i;
+
+#if defined(SMP_SERVER) && defined(OS_CYGWIN_NT)
+	// Handle lazy re-init of the thread-pool after a POSIX fork
+	if (unlikely(blas_server_avail == 0)) blas_thread_init();
+#endif
 
 	if (num_threads < 1) num_threads = blas_cpu_number;