Make the device clock members atomic

Even though they're protected by a SeqLock of sorts, it's still UB to read and
write non-atomic vars from different threads. It's fine to do relaxed reads and
writes given the lock though, to help alleviate the cost.

2 files changed, 19 insertions, 2 deletions

diff --git a/core/device.cpp b/core/device.cpp
index 2766c5e4..a5edf63c 100644
--- a/core/device.cpp
+++ b/core/device.cpp
@@ -9,6 +9,9 @@
 #include "mastering.h"
 
 
+static_assert(std::atomic<std::chrono::nanoseconds>::is_always_lock_free);
+
+
 al::FlexArray<ContextBase*> DeviceBase::sEmptyContextArray{0u};
 
 
diff --git a/core/device.h b/core/device.h
index 8abbef21..842f1d82 100644
--- a/core/device.h
+++ b/core/device.h
@@ -218,8 +218,8 @@ struct DeviceBase {
      */
     NfcFilter mNFCtrlFilter{};
 
-    uint SamplesDone{0u};
-    std::chrono::nanoseconds ClockBase{0};
+    std::atomic<uint> mSamplesDone{0u};
+    std::atomic<std::chrono::nanoseconds> mClockBase{std::chrono::nanoseconds{}};
     std::chrono::nanoseconds FixedLatency{0};
 
     AmbiRotateMatrix mAmbiRotateMatrix{};
@@ -307,6 +307,20 @@ struct DeviceBase {
         return refcount;
     }
 
+    /**
+     * Helper to get the current clock time from the device's ClockBase, and
+     * SamplesDone converted from the sample rate. Should only be called while
+     * watching the MixCount.
+     */
+    std::chrono::nanoseconds getClockTime() const noexcept
+    {
+        using std::chrono::seconds;
+        using std::chrono::nanoseconds;
+
+        auto ns = nanoseconds{seconds{mSamplesDone.load(std::memory_order_relaxed)}} / Frequency;
+        return mClockBase.load(std::memory_order_relaxed) + ns;
+    }
+
     void ProcessHrtf(const size_t SamplesToDo);
     void ProcessAmbiDec(const size_t SamplesToDo);
     void ProcessAmbiDecStablized(const size_t SamplesToDo);