-/* Copyright (c) 2012-2019. The SimGrid Team. All rights reserved. */
+/* Copyright (c) 2012-2023. 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. */
-#ifndef SIMIX_MUTEXIMPL_HPP
-#define SIMIX_MUTEXIMPL_HPP
+#ifndef SIMGRID_KERNEL_ACTIVITY_MUTEX_HPP
+#define SIMGRID_KERNEL_ACTIVITY_MUTEX_HPP
-#include "simgrid/s4u/ConditionVariable.hpp"
+#include "simgrid/s4u/Mutex.hpp"
+#include "src/kernel/activity/ActivityImpl.hpp"
#include "src/kernel/actor/ActorImpl.hpp"
#include <boost/intrusive/list.hpp>
-namespace simgrid {
-namespace kernel {
-namespace activity {
+namespace simgrid::kernel::activity {
+
+/** Mutex Acquisition: the act / process of acquiring the mutex.
+ *
+ * You can declare some interest on a mutex without being blocked waiting if it's already occupied.
+ * If it gets freed by its current owned, you become the new owner, even if you're still not blocked on it.
+ * Nobody can lock it behind your back or overpass you in the queue in any way, even if you're still not blocked on it.
+ *
+ * Afterward, when you do consider the lock, the test() or wait() operations are both non-blocking since you're the
+ * owner. People who declared interest in the mutex after you get stuck in the queue behind you.
+ *
+ *
+ * Splitting the locking process this way is interesting for symmetry with the other activities such as exec or
+ * communication that do have an async variant and could be mildly interesting to the users once exposed in S4U, but
+ * that's not the only reason. It's also very important to the MC world: the Mutex::lock_async() is always enabled
+ * (nothing can prevent you from adding yourself to the queue of potential owners) while Acquisition::wait() is
+ * persistent: it's not always enabled but once it gets enabled (because you're the owner), it remains enabled for ever.
+ *
+ * Mutex::lock() is not persistent: sometimes it's enabled if the mutex is free, and then it gets disabled if
+ * someone else locks the mutex, and then it becomes enabled again once the mutex is freed. This is why Mutex::lock()
+ * is not used in our MC computational model: we ban non-persistent transitions because they would make some
+ * computations much more complex.
+ *
+ * In particular, computing the extension of an unfolding's configuration is polynomial when you only have persistent
+ * transitions while it's O(2^n) when some of the transitions are non-persistent (you have to consider again all subsets
+ * of a set if some transitions may become disabled in between, while you don't have to reconsider them if you can reuse
+ * your previous computations).
+ */
+class XBT_PUBLIC MutexAcquisitionImpl : public ActivityImpl_T<MutexAcquisitionImpl> {
+ actor::ActorImpl* issuer_ = nullptr;
+ MutexImpl* mutex_ = nullptr;
+
+public:
+ MutexAcquisitionImpl(actor::ActorImpl* issuer, MutexImpl* mutex) : issuer_(issuer), mutex_(mutex) {}
+ MutexImplPtr get_mutex() { return mutex_; }
+ actor::ActorImpl* get_issuer() { return issuer_; }
+
+ bool test(actor::ActorImpl* issuer = nullptr) override;
+ void wait_for(actor::ActorImpl* issuer, double timeout) override;
+ void post() override
+ { /*no surf action*/
+ }
+ void finish() override;
+ void set_exception(actor::ActorImpl* issuer) override
+ { /* nothing to do */
+ }
+};
class XBT_PUBLIC MutexImpl {
+ std::atomic_int_fast32_t refcount_{1};
+ s4u::Mutex piface_;
+ actor::ActorImpl* owner_ = nullptr;
+ std::deque<MutexAcquisitionImplPtr> ongoing_acquisitions_;
+ static unsigned next_id_;
+ unsigned id_ = next_id_++;
+
+ friend MutexAcquisitionImpl;
+
public:
MutexImpl() : piface_(this) {}
MutexImpl(MutexImpl const&) = delete;
MutexImpl& operator=(MutexImpl const&) = delete;
- void lock(actor::ActorImpl* issuer);
+ MutexAcquisitionImplPtr lock_async(actor::ActorImpl* issuer);
bool try_lock(actor::ActorImpl* issuer);
void unlock(actor::ActorImpl* issuer);
+ unsigned get_id() const { return id_; }
- MutexImpl* ref();
- void unref();
- bool locked_ = false;
- actor::ActorImpl* owner_ = nullptr;
- // List of sleeping actors:
- actor::SynchroList sleeping_;
+ actor::ActorImpl* get_owner() const { return owner_; }
// boost::intrusive_ptr<Mutex> support:
friend void intrusive_ptr_add_ref(MutexImpl* mutex)
}
s4u::Mutex& mutex() { return piface_; }
-
-private:
- std::atomic_int_fast32_t refcount_{1};
- s4u::Mutex piface_;
};
-}
-}
-}
-#endif /* SIMIX_MUTEXIMPL_HPP */
+} // namespace simgrid::kernel::activity
+#endif
