From 5dfae0604bba1916578e847df3aa4f8e524cc1b7 Mon Sep 17 00:00:00 2001
From: Dirk Hoffmann <dirk.hoffmann@me.com>
Date: Sun, 22 Dec 2024 14:40:50 +0100
Subject: [PATCH] Added a mutex protecting texture accesses (#845)

---
 Emulator/Components/Denise/PixelEngine.cpp |  5 +++++
 Emulator/Components/Emulator.h             |  6 +++++-
 Emulator/VAmiga.cpp                        | 12 ++++++++++++
 Emulator/VAmiga.h                          | 14 ++++++++++++++
 Emulator/config.cpp                        |  2 +-
 GUI/Metal/Layers/Canvas.swift              |  8 ++++++++
 Proxy/EmulatorProxy.h                      |  2 ++
 Proxy/EmulatorProxy.mm                     | 10 ++++++++++
 8 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/Emulator/Components/Denise/PixelEngine.cpp b/Emulator/Components/Denise/PixelEngine.cpp
index 3aa716bbb..2b7b20179 100644
--- a/Emulator/Components/Denise/PixelEngine.cpp
+++ b/Emulator/Components/Denise/PixelEngine.cpp
@@ -13,6 +13,7 @@
 #include "Colors.h"
 #include "Denise.h"
 #include "DmaDebugger.h"
+#include "Emulator.h"
 
 #include <fstream>
 
@@ -309,6 +310,8 @@ PixelEngine::stablePtr(isize row, isize col)
 void
 PixelEngine::swapBuffers()
 {
+    emulator.textureLock.lock();
+
     videoPort.buffersWillSwap();
 
     isize oldActiveBuffer = activeBuffer;
@@ -319,6 +322,8 @@ PixelEngine::swapBuffers()
     emuTexture[newActiveBuffer].prevlof = emuTexture[oldActiveBuffer].lof;
 
     activeBuffer = newActiveBuffer;
+
+    emulator.textureLock.unlock();
 }
 
 void
diff --git a/Emulator/Components/Emulator.h b/Emulator/Components/Emulator.h
index 3b6af5d54..70e64841e 100644
--- a/Emulator/Components/Emulator.h
+++ b/Emulator/Components/Emulator.h
@@ -40,6 +40,9 @@ class Emulator : public Thread, public Synchronizable, public Inspectable<Emulat
     // Incoming external events
     CmdQueue cmdQueue;
 
+    // Texture lock
+    util::Mutex textureLock;
+
 
     //
     // Methods
@@ -157,7 +160,8 @@ class Emulator : public Thread, public Synchronizable, public Inspectable<Emulat
     //
 
     const FrameBuffer &getTexture() const;
-    
+    void lockTexture() { textureLock.lock(); }
+    void unlockTexture() { textureLock.unlock(); }
 
     //
     // Command queue
diff --git a/Emulator/VAmiga.cpp b/Emulator/VAmiga.cpp
index bb4091439..d3e456f08 100644
--- a/Emulator/VAmiga.cpp
+++ b/Emulator/VAmiga.cpp
@@ -811,6 +811,18 @@ SerialPortAPI::readOutgoingPrintableByte() const
 // Ports (VideoPort)
 //
 
+void
+VideoPortAPI::lockTexture()
+{
+    emu->lockTexture();
+}
+
+void
+VideoPortAPI::unlockTexture()
+{
+    emu->unlockTexture();
+}
+
 const u32 *
 VideoPortAPI::getTexture() const
 {
diff --git a/Emulator/VAmiga.h b/Emulator/VAmiga.h
index fe8bd8045..de4abf9ee 100644
--- a/Emulator/VAmiga.h
+++ b/Emulator/VAmiga.h
@@ -999,6 +999,20 @@ struct VideoPortAPI : public API {
     /// @name Retrieving video data
     /// @{
 
+    /** @brief  Locks the emulator texture
+     *
+     * This function aquires a mutex that prevents the emulator to modify the
+     * stable texture. Call this function prior to getTexture().
+     */
+    void lockTexture();
+
+    /** @brief  Unlocks the emulator texture
+     *
+     * This function releases the mutex acquired in lockTexture(). Call this
+     * function when the pointer returned by getTexture() is no longer needed.
+     */
+    void unlockTexture();
+
     /** @brief  Returns a pointer to the most recent stable texture
      *
      * The texture dimensions are given by constants vamiga::Texture::width
diff --git a/Emulator/config.cpp b/Emulator/config.cpp
index 68cb10e00..49a934a83 100644
--- a/Emulator/config.cpp
+++ b/Emulator/config.cpp
@@ -108,7 +108,7 @@ debugflag POSREG_DEBUG    = 0;
 debugflag JOYREG_DEBUG    = 0;
 debugflag POTREG_DEBUG    = 0;
 debugflag VID_DEBUG       = 0;
-debugflag PRT_DEBUG       = 1;
+debugflag PRT_DEBUG       = 0;
 debugflag SER_DEBUG       = 0;
 debugflag POT_DEBUG       = 0;
 debugflag HOLD_MOUSE_L    = 0;
diff --git a/GUI/Metal/Layers/Canvas.swift b/GUI/Metal/Layers/Canvas.swift
index b708358f7..3392fcc9a 100644
--- a/GUI/Metal/Layers/Canvas.swift
+++ b/GUI/Metal/Layers/Canvas.swift
@@ -237,6 +237,11 @@ class Canvas: Layer {
         // Get the emulator texture
         var buffer: UnsafePointer<u32>!
         var nr = 0
+
+        // Prevent the stable texture from changing
+        amiga.videoPort.lockTexture()
+
+        // Grab the stable texture
         amiga.videoPort.texture(&buffer, nr: &nr, lof: &currLOF, prevlof: &prevLOF)
 
         // Check for duplicated or dropped frames
@@ -255,6 +260,9 @@ class Canvas: Layer {
         } else {
             sfTexture.replace(w: Int(TPP) * HPIXELS, h: VPIXELS, buffer: buffer)
         }
+
+        // Release the texture lock
+        amiga.videoPort.unlockTexture()
     }
 
     //
diff --git a/Proxy/EmulatorProxy.h b/Proxy/EmulatorProxy.h
index 201e8b0a6..19b3adbe4 100644
--- a/Proxy/EmulatorProxy.h
+++ b/Proxy/EmulatorProxy.h
@@ -594,6 +594,8 @@
 
 @interface VideoPortProxy : CoreComponentProxy { }
 
+- (void)lockTexture;
+- (void)unlockTexture;
 - (void)texture:(const u32 **)ptr nr:(NSInteger *)nr lof:(bool *)lof prevlof:(bool *)prevlof;
 
 @end
diff --git a/Proxy/EmulatorProxy.mm b/Proxy/EmulatorProxy.mm
index 968cbaf9e..246542d2e 100644
--- a/Proxy/EmulatorProxy.mm
+++ b/Proxy/EmulatorProxy.mm
@@ -1081,6 +1081,16 @@ - (VideoPortAPI *)port
     return (VideoPortAPI *)obj;
 }
 
+- (void)lockTexture
+{
+    [self port]->lockTexture();
+}
+
+- (void)unlockTexture
+{
+    [self port]->unlockTexture();
+}
+
 - (void)texture:(const u32 **)ptr nr:(NSInteger *)nr lof:(bool *)lof prevlof:(bool *)prevlof
 {
     isize inr;