drm_hwcomposer: add AutoLock to automatically handle pthread_mutex_lock

For functions that need to hold locks and also handle errors, using AutoLock
will make them much simpler and less prone to mutex handling errors.

Change-Id: Ida6545850e89186c552e3d58b2973c14852494ad

3 files changed, 99 insertions, 0 deletions

diff --git a/Android.mk b/Android.mk
index ca94f4c..f9add2f 100644
--- a/Android.mk
+++ b/Android.mk
@@ -37,6 +37,7 @@ LOCAL_C_INCLUDES := \
 	system/core/libsync/include \
 
 LOCAL_SRC_FILES := \
+	autolock.cpp \
 	drmresources.cpp \
 	drmcomposition.cpp \
 	drmcompositor.cpp \
diff --git a/autolock.cpp b/autolock.cpp
new file mode 100644
index 0000000..1a2ded7
--- /dev/null
+++ b/autolock.cpp
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#define ATRACE_TAG ATRACE_TAG_GRAPHICS
+#define LOG_TAG "hwc-drm-auto-lock"
+
+#include "autolock.h"
+
+#include <errno.h>
+#include <pthread.h>
+
+#include <cutils/log.h>
+
+namespace android {
+
+int AutoLock::Lock() {
+  if (locked_) {
+    ALOGE("Invalid attempt to double lock AutoLock %s", name_);
+    return -EINVAL;
+  }
+  int ret = pthread_mutex_lock(mutex_);
+  if (ret) {
+    ALOGE("Failed to acquire %s lock %d", name_, ret);
+    return ret;
+  }
+  locked_ = true;
+  return 0;
+}
+
+int AutoLock::Unlock() {
+  if (!locked_) {
+    ALOGE("Invalid attempt to unlock unlocked AutoLock %s", name_);
+    return -EINVAL;
+  }
+  int ret = pthread_mutex_unlock(mutex_);
+  if (ret) {
+    ALOGE("Failed to release %s lock %d", name_, ret);
+    return ret;
+  }
+  locked_ = false;
+  return 0;
+}
+}
diff --git a/autolock.h b/autolock.h
new file mode 100644
index 0000000..3b824e2
--- /dev/null
+++ b/autolock.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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 <pthread.h>
+
+namespace android {
+
+class AutoLock {
+ public:
+  AutoLock(pthread_mutex_t *mutex, const char *const name)
+      : mutex_(mutex), name_(name) {
+  }
+  ~AutoLock() {
+    if (locked_)
+      Unlock();
+  }
+
+  AutoLock(const AutoLock &rhs) = delete;
+  AutoLock &operator=(const AutoLock &rhs) = delete;
+
+  int Lock();
+  int Unlock();
+
+ private:
+  pthread_mutex_t *const mutex_;
+  bool locked_ = false;
+  const char *const name_;
+};
+}