1 /* Copyright (c) 2010-2023. 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 /***************** Centralized Mutual Exclusion Algorithm *********************/
7 /* This example implements a centralized mutual exclusion algorithm. */
8 /* There is no bug on it, it is just provided to test the state space */
9 /* reduction of DPOR. */
10 /******************************************************************************/
12 #include "simgrid/s4u.hpp"
14 constexpr int AMOUNT_OF_CLIENTS = 4;
15 constexpr int CS_PER_PROCESS = 2;
17 XBT_LOG_NEW_DEFAULT_CATEGORY(centralized, "my log messages");
18 namespace sg4 = simgrid::s4u;
22 enum class Kind { GRANT, REQUEST, RELEASE };
23 Kind kind = Kind::GRANT;
24 sg4::Mailbox* return_mailbox = nullptr;
25 explicit Message(Message::Kind kind, sg4::Mailbox* mbox) : kind(kind), return_mailbox(mbox) {}
28 static void coordinator()
30 std::queue<sg4::Mailbox*> requests;
31 sg4::Mailbox* mbox = sg4::Mailbox::by_name("coordinator");
33 bool CS_used = false; // initially the CS is idle
34 int todo = AMOUNT_OF_CLIENTS * CS_PER_PROCESS; // amount of releases we are expecting
37 auto m = mbox->get_unique<Message>();
38 if (m->kind == Message::Kind::REQUEST) {
39 if (CS_used) { // need to push the request in the vector
40 XBT_INFO("CS already used. Queue the request");
41 requests.push(m->return_mailbox);
42 } else { // can serve it immediately
43 XBT_INFO("CS idle. Grant immediately");
44 m->return_mailbox->put(new Message(Message::Kind::GRANT, mbox), 1000);
47 } else { // that's a release. Check if someone was waiting for the lock
48 if (not requests.empty()) {
49 XBT_INFO("CS release. Grant to queued requests (queue size: %zu)", requests.size());
50 sg4::Mailbox* req = requests.front();
52 req->put(new Message(Message::Kind::GRANT, mbox), 1000);
54 } else { // nobody wants it
55 XBT_INFO("CS release. resource now idle");
61 XBT_INFO("Received all releases, quit now");
66 aid_t my_pid = sg4::this_actor::get_pid();
68 sg4::Mailbox* my_mailbox = sg4::Mailbox::by_name(std::to_string(my_pid));
70 // request the CS 3 times, sleeping a bit in between
71 for (int i = 0; i < CS_PER_PROCESS; i++) {
72 XBT_INFO("Ask the request");
73 sg4::Mailbox::by_name("coordinator")->put(new Message(Message::Kind::REQUEST, my_mailbox), 1000);
74 // wait for the answer
75 auto grant = my_mailbox->get_unique<Message>();
76 XBT_INFO("got the answer. Sleep a bit and release it");
77 sg4::this_actor::sleep_for(1);
79 sg4::Mailbox::by_name("coordinator")->put(new Message(Message::Kind::RELEASE, my_mailbox), 1000);
80 sg4::this_actor::sleep_for(static_cast<double>(my_pid));
82 XBT_INFO("Got all the CS I wanted, quit now");
85 int main(int argc, char* argv[])
87 sg4::Engine e(&argc, argv);
89 e.load_platform(argv[1]);
91 sg4::Actor::create("coordinator", e.host_by_name("Tremblay"), coordinator);
92 sg4::Actor::create("client", e.host_by_name("Fafard"), client);
93 sg4::Actor::create("client", e.host_by_name("Boivin"), client);
94 sg4::Actor::create("client", e.host_by_name("Jacquelin"), client);
95 sg4::Actor::create("client", e.host_by_name("Ginette"), client);