Mark waitForMix as (potentially) blocking

Author: kcat

common/opthelpers.h

@@ -64,8 +64,10 @@
 
 #if HAS_ATTRIBUTE(clang::nonblocking) && !defined(_MSVC_STL_UPDATE)
 #define NONBLOCKING [[clang::nonblocking]]
+#define BLOCKING [[clang::blocking]]
 #else
 #define NONBLOCKING
+#define BLOCKING
 #endif
 
 #if defined(__clang__) && (__clang_major__ >= (defined(__APPLE__) ? 17 : 20))

core/device.h

@@ -360,7 +360,7 @@ struct DeviceBase {
     }
 
     /** Waits for the mixer to not be mixing or updating the clock. */
-    [[nodiscard]] auto waitForMix() const noexcept -> unsigned
+    [[nodiscard]] auto waitForMix() const noexcept BLOCKING -> unsigned
     {
         auto refcount = mMixCount.load(std::memory_order_acquire);
         while((refcount&1)) refcount = mMixCount.load(std::memory_order_acquire);