Merge pull request #256 from Flamefire/master

[simgrid.git] / include / simgrid / s4u / Mutex.hpp

diff --git a/include/simgrid/s4u/Mutex.hpp b/include/simgrid/s4u/Mutex.hpp
index 241ae36..6d58988 100644 (file)
--- a/include/simgrid/s4u/Mutex.hpp
+++ b/include/simgrid/s4u/Mutex.hpp
@@ -1,4 +1,4 @@
-/* Copyright (c) 2006-2015. The SimGrid Team. All rights reserved.          */
+/* Copyright (c) 2006-2018. The SimGrid Team. All rights reserved.          */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
@@ -19,14 +19,27 @@ namespace s4u {
 
 class ConditionVariable;
 
-XBT_PUBLIC_CLASS Mutex {
-friend ConditionVariable;
-private:
-  friend simgrid::simix::Mutex;
-  simgrid::simix::Mutex* mutex_;
-  Mutex(simgrid::simix::Mutex* mutex) : mutex_(mutex) {}
-public:
+/** @brief A classical mutex, but blocking in the simulation world
+ *  @ingroup s4u_api
+ *
+ * It is strictly impossible to use a real mutex, such as
+ * <a href="http://en.cppreference.com/w/cpp/thread/mutex">std::mutex</a>
+ * or <a href="http://pubs.opengroup.org/onlinepubs/007908775/xsh/pthread_mutex_lock.html">pthread_mutex_t</a>,
+ * because it would block the whole simulation.
+ * Instead, you should use the present class, that is a drop-in replacement of
+ * <a href="http://en.cppreference.com/w/cpp/thread/mutex>std::mutex</a>.
+ *
+ * As for any S4U object, Mutexes are using the @ref s4u_raii "RAII idiom" for memory management.
+ * Use createMutex() to get a ::MutexPtr to a newly created mutex and only manipulate ::MutexPtr.
+ *
+ */
+class XBT_PUBLIC Mutex {
+  friend ConditionVariable;
+  friend simgrid::kernel::activity::MutexImpl;
+  simgrid::kernel::activity::MutexImpl* mutex_;
+  explicit Mutex(simgrid::kernel::activity::MutexImpl * mutex) : mutex_(mutex) {}
 
+  /* refcounting of the intrusive_ptr is delegated to the implementation object */
   friend void intrusive_ptr_add_ref(Mutex* mutex)
   {
     xbt_assert(mutex);
@@ -37,15 +50,18 @@ public:
     xbt_assert(mutex);
     SIMIX_mutex_unref(mutex->mutex_);
   }
+public:
   using Ptr = boost::intrusive_ptr<Mutex>;
 
   // No copy:
+  /** You cannot create a new mutex by copying an existing one. Use MutexPtr instead */
   Mutex(Mutex const&) = delete;
+  /** You cannot create a new mutex by value assignment either. Use MutexPtr instead */
   Mutex& operator=(Mutex const&) = delete;
 
+  /** Constructs a new mutex */
   static Ptr createMutex();
 
-public:
   void lock();
   void unlock();
   bool try_lock();