docker swarm

builder-docker/jenkins/node-v18.20.2-linux-x64/include/node/v8-locker.h

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+// Copyright 2021 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef INCLUDE_V8_LOCKER_H_
+#define INCLUDE_V8_LOCKER_H_
+
+#include "v8config.h"  // NOLINT(build/include_directory)
+
+namespace v8 {
+
+namespace internal {
+class Isolate;
+}  // namespace internal
+
+class Isolate;
+
+/**
+ * Multiple threads in V8 are allowed, but only one thread at a time is allowed
+ * to use any given V8 isolate, see the comments in the Isolate class. The
+ * definition of 'using a V8 isolate' includes accessing handles or holding onto
+ * object pointers obtained from V8 handles while in the particular V8 isolate.
+ * It is up to the user of V8 to ensure, perhaps with locking, that this
+ * constraint is not violated. In addition to any other synchronization
+ * mechanism that may be used, the v8::Locker and v8::Unlocker classes must be
+ * used to signal thread switches to V8.
+ *
+ * v8::Locker is a scoped lock object. While it's active, i.e. between its
+ * construction and destruction, the current thread is allowed to use the locked
+ * isolate. V8 guarantees that an isolate can be locked by at most one thread at
+ * any time. In other words, the scope of a v8::Locker is a critical section.
+ *
+ * Sample usage:
+ * \code
+ * ...
+ * {
+ *   v8::Locker locker(isolate);
+ *   v8::Isolate::Scope isolate_scope(isolate);
+ *   ...
+ *   // Code using V8 and isolate goes here.
+ *   ...
+ * } // Destructor called here
+ * \endcode
+ *
+ * If you wish to stop using V8 in a thread A you can do this either by
+ * destroying the v8::Locker object as above or by constructing a v8::Unlocker
+ * object:
+ *
+ * \code
+ * {
+ *   isolate->Exit();
+ *   v8::Unlocker unlocker(isolate);
+ *   ...
+ *   // Code not using V8 goes here while V8 can run in another thread.
+ *   ...
+ * } // Destructor called here.
+ * isolate->Enter();
+ * \endcode
+ *
+ * The Unlocker object is intended for use in a long-running callback from V8,
+ * where you want to release the V8 lock for other threads to use.
+ *
+ * The v8::Locker is a recursive lock, i.e. you can lock more than once in a
+ * given thread. This can be useful if you have code that can be called either
+ * from code that holds the lock or from code that does not. The Unlocker is
+ * not recursive so you can not have several Unlockers on the stack at once, and
+ * you cannot use an Unlocker in a thread that is not inside a Locker's scope.
+ *
+ * An unlocker will unlock several lockers if it has to and reinstate the
+ * correct depth of locking on its destruction, e.g.:
+ *
+ * \code
+ * // V8 not locked.
+ * {
+ *   v8::Locker locker(isolate);
+ *   Isolate::Scope isolate_scope(isolate);
+ *   // V8 locked.
+ *   {
+ *     v8::Locker another_locker(isolate);
+ *     // V8 still locked (2 levels).
+ *     {
+ *       isolate->Exit();
+ *       v8::Unlocker unlocker(isolate);
+ *       // V8 not locked.
+ *     }
+ *     isolate->Enter();
+ *     // V8 locked again (2 levels).
+ *   }
+ *   // V8 still locked (1 level).
+ * }
+ * // V8 Now no longer locked.
+ * \endcode
+ */
+class V8_EXPORT Unlocker {
+ public:
+  /**
+   * Initialize Unlocker for a given Isolate.
+   */
+  V8_INLINE explicit Unlocker(Isolate* isolate) { Initialize(isolate); }
+
+  ~Unlocker();
+
+ private:
+  void Initialize(Isolate* isolate);
+
+  internal::Isolate* isolate_;
+};
+
+class V8_EXPORT Locker {
+ public:
+  /**
+   * Initialize Locker for a given Isolate.
+   */
+  V8_INLINE explicit Locker(Isolate* isolate) { Initialize(isolate); }
+
+  ~Locker();
+
+  /**
+   * Returns whether or not the locker for a given isolate, is locked by the
+   * current thread.
+   */
+  static bool IsLocked(Isolate* isolate);
+
+  /**
+   * Returns whether any v8::Locker has ever been used in this process.
+   * TODO(cbruni, chromium:1240851): Fix locking checks on a per-thread basis.
+   * The current implementation is quite confusing and leads to unexpected
+   * results if anybody uses v8::Locker in the current process.
+   */
+  V8_DEPRECATE_SOON("This method will be removed.")
+  static bool WasEverUsed();
+  V8_DEPRECATED("Use WasEverUsed instead")
+  static bool IsActive();
+
+  // Disallow copying and assigning.
+  Locker(const Locker&) = delete;
+  void operator=(const Locker&) = delete;
+
+ private:
+  void Initialize(Isolate* isolate);
+
+  bool has_lock_;
+  bool top_level_;
+  internal::Isolate* isolate_;
+};
+
+}  // namespace v8
+
+#endif  // INCLUDE_V8_LOCKER_H_