Import of the watch repository from Pebble

src/fw/comm/bt_lock.c

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "bt_lock.h"
+
+#include "system/passert.h"
+
+#include "portmacro.h"
+
+// NOTE: The s_bt_lock is the global Bluetooth lock that is used by the firmware
+// *and* by Bluetopia. It gets handed to Bluetopia using bt_lock_get() in
+// BTPSKRNL.c when Bluetopia is initialized. The firmware uses this lock to
+// protect Bluetooth-related state that is read and written from the Bluetooth
+// callback task (PebbleTask_BTCallback) and other tasks. If we created our
+// own mutex for this purpose, we would encounter dead-lock situations.
+// For example:
+//   Task1: Bluetopia code -> grabs BT stack lock -> Pebble callback -> grabs pebble mutex
+//   Task2: Pebble code -> grabs pebble mutex -> calls into Bluetopia -> tries to grab BT stack lock
+
+static PebbleRecursiveMutex *s_bt_lock;
+
+void bt_lock_init(void) {
+  // Never free'd.
+  PBL_ASSERTN(!s_bt_lock);
+  s_bt_lock = mutex_create_recursive();
+}
+
+PebbleRecursiveMutex *bt_lock_get(void) {
+  return s_bt_lock;
+}
+
+void bt_lock(void) {
+  register uint32_t LR __asm ("lr");
+  uint32_t myLR = LR;
+  mutex_lock_recursive_with_timeout_and_lr(s_bt_lock, portMAX_DELAY, myLR);
+}
+
+void bt_unlock(void) {
+  mutex_unlock_recursive(s_bt_lock);
+}
+
+void bt_lock_assert_held(bool is_held) {
+  mutex_assert_recursive_held_by_curr_task(s_bt_lock, is_held);
+}
+
+bool bt_lock_is_held(void) {
+  return mutex_is_owned_recursive(s_bt_lock);
+}