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authorPedro J. Estébanez <pedrojrulez@gmail.com>2023-02-20 18:57:31 +0100
committerPedro J. Estébanez <pedrojrulez@gmail.com>2023-02-20 20:43:31 +0100
commitdaa29d1007f1f3ab630be7f412aa09c714cdf037 (patch)
tree072a197f5e3fd06aa95e1f645ddabc2f01aac1b1
parent9f68d06ec2d8dbeb237c5aa5c6f9bbcbe26bde5d (diff)
Implement ConditionVariable
-rw-r--r--core/os/condition_variable.h60
-rw-r--r--core/os/mutex.h69
2 files changed, 122 insertions, 7 deletions
diff --git a/core/os/condition_variable.h b/core/os/condition_variable.h
new file mode 100644
index 0000000000..6037ff327d
--- /dev/null
+++ b/core/os/condition_variable.h
@@ -0,0 +1,60 @@
+/**************************************************************************/
+/* condition_variable.h */
+/**************************************************************************/
+/* This file is part of: */
+/* GODOT ENGINE */
+/* https://godotengine.org */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
+/* */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the */
+/* "Software"), to deal in the Software without restriction, including */
+/* without limitation the rights to use, copy, modify, merge, publish, */
+/* distribute, sublicense, and/or sell copies of the Software, and to */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions: */
+/* */
+/* The above copyright notice and this permission notice shall be */
+/* included in all copies or substantial portions of the Software. */
+/* */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
+/**************************************************************************/
+
+#ifndef CONDITION_VARIABLE_H
+#define CONDITION_VARIABLE_H
+
+#include <condition_variable>
+
+// An object one or multiple threads can wait on a be notified by some other.
+// Normally, you want to use a semaphore for such scenarios, but when the
+// condition is something different than a count being greater than zero
+// (which is the built-in logic in a semaphore) or you want to provide your
+// own mutex to tie the wait-notify to some other behavior, you need to use this.
+
+class ConditionVariable {
+ mutable std::condition_variable condition;
+
+public:
+ template <class BinaryMutexT>
+ _ALWAYS_INLINE_ void wait(const MutexLock<BinaryMutexT> &p_lock) const {
+ condition.wait(const_cast<std::unique_lock<std::mutex> &>(p_lock.lock));
+ }
+
+ _ALWAYS_INLINE_ void notify_one() const {
+ condition.notify_one();
+ }
+
+ _ALWAYS_INLINE_ void notify_all() const {
+ condition.notify_all();
+ }
+};
+
+#endif // CONDITION_VARIABLE_H
diff --git a/core/os/mutex.h b/core/os/mutex.h
index ceedcb235a..90cc1632e8 100644
--- a/core/os/mutex.h
+++ b/core/os/mutex.h
@@ -31,12 +31,20 @@
#ifndef MUTEX_H
#define MUTEX_H
+#include "core/error/error_macros.h"
#include "core/typedefs.h"
#include <mutex>
+template <class MutexT>
+class MutexLock;
+
template <class StdMutexT>
class MutexImpl {
+ friend class MutexLock<MutexImpl<StdMutexT>>;
+
+ using StdMutexType = StdMutexT;
+
mutable StdMutexT mutex;
public:
@@ -53,18 +61,65 @@ public:
}
};
+// A very special kind of mutex, used in scenarios where these
+// requirements hold at the same time:
+// - Must be used with a condition variable (only binary mutexes are suitable).
+// - Must have recursive semnantics (or simulate, as this one does).
+// The implementation keeps the lock count in TS. Therefore, only
+// one object of each version of the template can exists; hence the Tag argument.
+// Tags must be unique across the Godot codebase.
+// Also, don't forget to declare the thread_local variable on each use.
+template <int Tag>
+class SafeBinaryMutex {
+ friend class MutexLock<SafeBinaryMutex>;
+
+ using StdMutexType = std::mutex;
+
+ mutable std::mutex mutex;
+ static thread_local uint32_t count;
+
+public:
+ _ALWAYS_INLINE_ void lock() const {
+ if (++count == 1) {
+ mutex.lock();
+ }
+ }
+
+ _ALWAYS_INLINE_ void unlock() const {
+ DEV_ASSERT(count);
+ if (--count == 0) {
+ mutex.unlock();
+ }
+ }
+
+ _ALWAYS_INLINE_ bool try_lock() const {
+ if (count) {
+ count++;
+ return true;
+ } else {
+ if (mutex.try_lock()) {
+ count++;
+ return true;
+ } else {
+ return false;
+ }
+ }
+ }
+
+ ~SafeBinaryMutex() {
+ DEV_ASSERT(!count);
+ }
+};
+
template <class MutexT>
class MutexLock {
- const MutexT &mutex;
+ friend class ConditionVariable;
+
+ std::unique_lock<typename MutexT::StdMutexType> lock;
public:
_ALWAYS_INLINE_ explicit MutexLock(const MutexT &p_mutex) :
- mutex(p_mutex) {
- mutex.lock();
- }
-
- _ALWAYS_INLINE_ ~MutexLock() {
- mutex.unlock();
+ lock(p_mutex.mutex) {
}
};