diff --git a/contrib/llvm-project/libcxx/src/atomic.cpp b/contrib/llvm-project/libcxx/src/atomic.cpp
index 250d33e98b02..e7496fa43666 100644
--- a/contrib/llvm-project/libcxx/src/atomic.cpp
+++ b/contrib/llvm-project/libcxx/src/atomic.cpp
@@ -26,6 +26,11 @@
 # define SYS_futex SYS_futex_time64
 #endif
 
+#elif defined(__FreeBSD__)
+
+#include <sys/types.h>
+#include <sys/umtx.h>
+
 #else // <- Add other operating systems here
 
 // Baseline needs no new headers
@@ -72,6 +77,22 @@ static void __libcpp_platform_wake_by_address(__cxx_atomic_contention_t const vo
                  const_cast<__cxx_atomic_contention_t*>(__ptr), 0);
 }
 
+#elif defined(__FreeBSD__) && defined(__LP64__)
+
+static void __libcpp_platform_wait_on_address(__cxx_atomic_contention_t const volatile* __ptr,
+                                              __cxx_contention_t __val)
+{
+    _umtx_op(const_cast<__cxx_atomic_contention_t*>(__ptr),
+      UMTX_OP_WAIT, __val, NULL, NULL);
+}
+
+static void __libcpp_platform_wake_by_address(__cxx_atomic_contention_t const volatile* __ptr,
+                                              bool __notify_one)
+{
+    _umtx_op(const_cast<__cxx_atomic_contention_t*>(__ptr),
+      UMTX_OP_WAKE, __notify_one ? 1 : INT_MAX, NULL, NULL);
+}
+
 #else // <- Add other operating systems here
 
 // Baseline is just a timed backoff