Make use of pthread_set_name_np(3) on FreeBSD.

include/jemalloc/internal/jemalloc_internal_decls.h

@@ -31,6 +31,9 @@
 #    include <sys/uio.h>
 #  endif
 #  include <pthread.h>
+#  ifdef __FreeBSD__
+#  include <pthread_np.h>
+#  endif
 #  include <signal.h>
 #  ifdef JEMALLOC_OS_UNFAIR_LOCK
 #    include <os/lock.h>

src/background_thread.c

@@ -509,6 +509,8 @@ background_thread_entry(void *ind_arg) {
 	assert(thread_ind < max_background_threads);
 #ifdef JEMALLOC_HAVE_PTHREAD_SETNAME_NP
 	pthread_setname_np(pthread_self(), "jemalloc_bg_thd");
+#elif defined(__FreeBSD__)
+	pthread_set_name_np(pthread_self(), "jemalloc_bg_thd");
 #endif
 	if (opt_percpu_arena != percpu_arena_disabled) {
 		set_current_thread_affinity((int)thread_ind);