1 /* Copyright (c) 2007-2022. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #ifndef SIMGRID_SIMIX_HPP
8 #define SIMGRID_SIMIX_HPP
10 #include <simgrid/s4u/Actor.hpp>
11 #include <xbt/promise.hpp>
12 #include <xbt/signal.hpp>
15 #include <unordered_map>
17 XBT_PUBLIC void simcall_run_answered(std::function<void()> const& code,
18 simgrid::kernel::actor::SimcallObserver* observer);
19 XBT_PUBLIC void simcall_run_blocking(std::function<void()> const& code,
20 simgrid::kernel::actor::SimcallObserver* observer);
26 /** Execute some code in kernel context on behalf of the user code.
28 * Every modification of the environment must be protected this way: every setter, constructor and similar.
29 * Getters don't have to be protected this way.
31 * This allows deterministic parallel simulation without any locking, even if almost nobody uses parallel simulation in
32 * SimGrid. More interestingly it makes every modification of the simulated world observable by the model-checker,
33 * allowing the whole MC business.
35 * It is highly inspired from the syscalls in a regular operating system, allowing the user code to get some specific
36 * code executed in the kernel context. But here, there is almost no security involved. Parameters get checked for
37 * finiteness but that's all. The main goal remain to ensure reproducible ordering of uncomparable events (in
38 * [parallel] simulation) and observability of events (in model-checking).
40 * The code passed as argument is supposed to terminate at the exact same simulated timestamp.
41 * Do not use it if your code may block waiting for a subsequent event, e.g. if you lock a mutex,
42 * you may need to wait for that mutex to be unlocked by its current owner.
43 * Potentially blocking simcall must be issued using simcall_blocking(), right below in this file.
45 template <class F> typename std::result_of_t<F()> simcall_answered(F&& code, SimcallObserver* observer = nullptr)
47 // If we are in the maestro, we take the fast path and execute the
48 // code directly without simcall marshalling/unmarshalling/dispatch:
49 if (s4u::Actor::is_maestro())
50 return std::forward<F>(code)();
52 // If we are in the application, pass the code to the maestro which
53 // executes it for us and reports the result. We use a std::future which
54 // conveniently handles the success/failure value for us.
55 using R = typename std::result_of_t<F()>;
56 simgrid::xbt::Result<R> result;
57 simcall_run_answered([&result, &code] { simgrid::xbt::fulfill_promise(result, std::forward<F>(code)); }, observer);
61 /** Execute some code (that does not return immediately) in kernel context
63 * This is very similar to simcall() right above, but the calling actor will not get rescheduled until
64 * actor->simcall_answer() is called explicitly.
66 * This is meant for blocking actions. For example, locking a mutex is a blocking simcall.
67 * First it's a simcall because that's obviously a modification of the world. Then, that's a blocking simcall because if
68 * the mutex happens not to be free, the actor is added to a queue of actors in the mutex. Every mutex->unlock() takes
69 * the first actor from the queue, mark it as current owner of the mutex and call actor->simcall_answer() to mark that
70 * this mutex is now unblocked and ready to run again. If the mutex is initially free, the calling actor is unblocked
71 * right away with actor->simcall_answer() once the mutex is marked as locked.
73 * If your code never calls actor->simcall_answer() itself, the actor will never return from its simcall.
75 * The return value is obtained from observer->get_result() if it exists. Otherwise void is returned.
77 template <class F> void simcall_blocking(F&& code, SimcallObserver* observer = nullptr)
79 xbt_assert(not s4u::Actor::is_maestro(), "Cannot execute blocking call in kernel mode");
81 // Pass the code to the maestro which executes it for us and reports the result. We use a std::future which
82 // conveniently handles the success/failure value for us.
83 simgrid::xbt::Result<void> result;
84 simcall_run_blocking([&result, &code] { simgrid::xbt::fulfill_promise(result, std::forward<F>(code)); }, observer);
85 result.get(); // rethrow stored exception if any
88 template <class F, class Observer>
89 auto simcall_blocking(F&& code, Observer* observer) -> decltype(observer->get_result())
91 simcall_blocking(std::forward<F>(code), static_cast<SimcallObserver*>(observer));
92 return observer->get_result();
96 } // namespace simgrid