1 /* Copyright (c) 2019-2022. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #ifndef SIMGRID_KERNEL_ACTIVITY_SEMAPHOREIMPL_HPP
7 #define SIMGRID_KERNEL_ACTIVITY_SEMAPHOREIMPL_HPP
10 #include <boost/intrusive/list.hpp>
12 #include "simgrid/s4u/Semaphore.hpp"
13 #include "src/kernel/actor/ActorImpl.hpp"
19 /** Semaphore Acquisition: the act / process of acquiring the semaphore.
21 * You can declare some interest on a semaphore without being blocked waiting if it's already empty.
22 * See the documentation of the MutexAcquisitionImpl for further details.
24 class XBT_PUBLIC SemAcquisitionImpl : public ActivityImpl_T<SemAcquisitionImpl> {
25 actor::ActorImpl* issuer_ = nullptr;
26 SemaphoreImpl* semaphore_ = nullptr;
27 bool granted_ = false;
32 SemAcquisitionImpl(actor::ActorImpl* issuer, SemaphoreImpl* sem) : issuer_(issuer), semaphore_(sem) {}
33 SemaphoreImplPtr get_semaphore() { return semaphore_; }
34 actor::ActorImpl* get_issuer() { return issuer_; }
36 bool test(actor::ActorImpl* issuer = nullptr) override { return granted_; }
37 void wait_for(actor::ActorImpl* issuer, double timeout) override;
39 void finish() override;
40 void set_exception(actor::ActorImpl* issuer) override
45 class XBT_PUBLIC SemaphoreImpl {
46 std::atomic_int_fast32_t refcount_{1};
47 s4u::Semaphore piface_;
49 std::deque<SemAcquisitionImplPtr> sleeping_; /* ongoing acquisitions */
51 friend SemAcquisitionImpl;
54 explicit SemaphoreImpl(unsigned int value) : piface_(this), value_(value){};
56 SemaphoreImpl(SemaphoreImpl const&) = delete;
57 SemaphoreImpl& operator=(SemaphoreImpl const&) = delete;
59 SemAcquisitionImplPtr acquire_async(actor::ActorImpl* issuer);
61 bool would_block() const { return (value_ == 0); }
63 unsigned int get_capacity() const { return value_; }
64 bool is_used() const { return not sleeping_.empty(); }
66 friend void intrusive_ptr_add_ref(SemaphoreImpl* sem)
68 XBT_ATTRIB_UNUSED auto previous = sem->refcount_.fetch_add(1);
69 xbt_assert(previous != 0);
71 friend void intrusive_ptr_release(SemaphoreImpl* sem)
73 if (sem->refcount_.fetch_sub(1) == 1) {
74 xbt_assert(not sem->is_used(), "Cannot destroy semaphore since someone is still using it");
79 s4u::Semaphore& sem() { return piface_; }
81 } // namespace activity
83 } // namespace simgrid
85 #endif /* SIMGRID_KERNEL_ACTIVITY_SEMAPHOREIMPL_HPP */