Fix BLE semaphore leak in Bluefruit library

Patches Bluefruit library to fix semaphore leak bug that causes device lockup
when BLE central disconnects unexpectedly (e.g., going out of range, supervision timeout).

Co-authored-by: Liam Cottle <[email protected]>
Co-authored-by: oltaco <[email protected]>

arch/nrf52/extra_scripts/patch_bluefruit.py

@@ -0,0 +1,198 @@
+"""
+Bluefruit BLE Patch Script
+
+Patches Bluefruit library to fix semaphore leak bug that causes device lockup
+when BLE central disconnects unexpectedly (e.g., going out of range, supervision timeout).
+
+Patches applied:
+1. BLEConnection.h: Add _hvn_qsize member to track semaphore queue size
+2. BLEConnection.cpp: Store hvn_qsize and restore semaphore on disconnect
+
+Bug description:
+- When a BLE central disconnects unexpectedly (reason=8 supervision timeout),
+  the BLE_GATTS_EVT_HVN_TX_COMPLETE event may never fire
+- This leaves the _hvn_sem counting semaphore in a decremented state
+- Since BLEConnection objects are reused (destructor never called), the
+  semaphore count is never restored
+- Eventually all semaphore counts are exhausted and notify() blocks/fails
+
+"""
+
+from pathlib import Path
+
+Import("env")  # pylint: disable=undefined-variable
+
+
+def _patch_ble_connection_header(source: Path) -> bool:
+    """
+    Add _hvn_qsize member variable to BLEConnection class.
+    
+    This is needed to restore the semaphore to its correct count on disconnect.
+    
+    Returns True if patch was applied or already applied, False on error.
+    """
+    try:
+        content = source.read_text()
+        
+        # Check if already patched
+        if "_hvn_qsize" in content:
+            return True  # Already patched
+        
+        # Find the location to insert - after _phy declaration
+        original_pattern = '''    uint8_t  _phy;
+
+    uint8_t  _role;'''
+        
+        patched_pattern = '''    uint8_t  _phy;
+    uint8_t  _hvn_qsize;
+
+    uint8_t  _role;'''
+        
+        if original_pattern not in content:
+            print("Bluefruit patch: WARNING - BLEConnection.h pattern not found")
+            return False
+        
+        content = content.replace(original_pattern, patched_pattern)
+        source.write_text(content)
+        
+        # Verify
+        if "_hvn_qsize" not in source.read_text():
+            return False
+        
+        return True
+    except Exception as e:
+        print(f"Bluefruit patch: ERROR patching BLEConnection.h: {e}")
+        return False
+
+
+def _patch_ble_connection_source(source: Path) -> bool:
+    """
+    Patch BLEConnection.cpp to:
+    1. Store hvn_qsize in constructor
+    2. Restore _hvn_sem semaphore to full count on disconnect
+    
+    Returns True if patch was applied or already applied, False on error.
+    """
+    try:
+        content = source.read_text()
+        
+        # Check if already patched (look for the restore loop)
+        if "uxSemaphoreGetCount(_hvn_sem)" in content:
+            return True  # Already patched
+        
+        # Patch 1: Store queue size in constructor
+        constructor_original = '''  _hvn_sem   = xSemaphoreCreateCounting(hvn_qsize, hvn_qsize);'''
+        
+        constructor_patched = '''  _hvn_qsize = hvn_qsize;
+  _hvn_sem   = xSemaphoreCreateCounting(hvn_qsize, hvn_qsize);'''
+        
+        if constructor_original not in content:
+            print("Bluefruit patch: WARNING - BLEConnection.cpp constructor pattern not found")
+            return False
+        
+        content = content.replace(constructor_original, constructor_patched)
+        
+        # Patch 2: Restore semaphore on disconnect
+        disconnect_original = '''    case BLE_GAP_EVT_DISCONNECTED:
+      // mark as disconnected
+      _connected = false;
+    break;'''
+        
+        disconnect_patched = '''    case BLE_GAP_EVT_DISCONNECTED:
+      // Restore notification semaphore to full count
+      // This fixes lockup when disconnect occurs with notifications in flight
+      while (uxSemaphoreGetCount(_hvn_sem) < _hvn_qsize) {
+        xSemaphoreGive(_hvn_sem);
+      }
+      // Release indication semaphore if waiting
+      if (_hvc_sem) {
+        _hvc_received = false;
+        xSemaphoreGive(_hvc_sem);
+      }
+      // mark as disconnected
+      _connected = false;
+    break;'''
+        
+        if disconnect_original not in content:
+            print("Bluefruit patch: WARNING - BLEConnection.cpp disconnect pattern not found")
+            return False
+        
+        content = content.replace(disconnect_original, disconnect_patched)
+        source.write_text(content)
+        
+        # Verify
+        verify_content = source.read_text()
+        if "uxSemaphoreGetCount(_hvn_sem)" not in verify_content:
+            return False
+        if "_hvn_qsize = hvn_qsize" not in verify_content:
+            return False
+        
+        return True
+    except Exception as e:
+        print(f"Bluefruit patch: ERROR patching BLEConnection.cpp: {e}")
+        return False
+
+
+def _apply_bluefruit_patches(target, source, env):  # pylint: disable=unused-argument
+    framework_path = env.get("PLATFORMFW_DIR")
+    if not framework_path:
+        framework_path = env.PioPlatform().get_package_dir("framework-arduinoadafruitnrf52")
+
+    if not framework_path:
+        print("Bluefruit patch: ERROR - framework directory not found")
+        env.Exit(1)
+        return
+
+    framework_dir = Path(framework_path)
+    bluefruit_lib = framework_dir / "libraries" / "Bluefruit52Lib" / "src"
+    patch_failed = False
+    
+    # Patch BLEConnection.h
+    conn_header = bluefruit_lib / "BLEConnection.h"
+    if conn_header.exists():
+        before = conn_header.read_text()
+        success = _patch_ble_connection_header(conn_header)
+        after = conn_header.read_text()
+        
+        if success:
+            if before != after:
+                print("Bluefruit patch: OK - Applied BLEConnection.h fix (added _hvn_qsize member)")
+            else:
+                print("Bluefruit patch: OK - BLEConnection.h already patched")
+        else:
+            print("Bluefruit patch: FAILED - BLEConnection.h")
+            patch_failed = True
+    else:
+        print(f"Bluefruit patch: ERROR - BLEConnection.h not found at {conn_header}")
+        patch_failed = True
+    
+    # Patch BLEConnection.cpp
+    conn_source = bluefruit_lib / "BLEConnection.cpp"
+    if conn_source.exists():
+        before = conn_source.read_text()
+        success = _patch_ble_connection_source(conn_source)
+        after = conn_source.read_text()
+        
+        if success:
+            if before != after:
+                print("Bluefruit patch: OK - Applied BLEConnection.cpp fix (restore semaphore on disconnect)")
+            else:
+                print("Bluefruit patch: OK - BLEConnection.cpp already patched")
+        else:
+            print("Bluefruit patch: FAILED - BLEConnection.cpp")
+            patch_failed = True
+    else:
+        print(f"Bluefruit patch: ERROR - BLEConnection.cpp not found at {conn_source}")
+        patch_failed = True
+    
+    if patch_failed:
+        print("Bluefruit patch: CRITICAL - Patch failed! Build aborted.")
+        env.Exit(1)
+
+
+# Register the patch to run before build
+bluefruit_action = env.VerboseAction(_apply_bluefruit_patches, "Applying Bluefruit BLE patches...")
+env.AddPreAction("$BUILD_DIR/${PROGNAME}.elf", bluefruit_action)
+
+# Also run immediately to patch before any compilation
+_apply_bluefruit_patches(None, None, env)

platformio.ini

@@ -79,7 +79,9 @@ extends = arduino_base
 platform = nordicnrf52
 platform_packages =
   framework-arduinoadafruitnrf52 @ 1.10700.0
-extra_scripts = create-uf2.py
+extra_scripts = 
+  create-uf2.py
+  arch/nrf52/extra_scripts/patch_bluefruit.py
 build_flags = ${arduino_base.build_flags}
   -D NRF52_PLATFORM
   -D LFS_NO_ASSERT=1