1 /* Context switching within the JVM. */
3 /* Copyright (c) 2009-2017. The SimGrid Team. All rights reserved. */
5 /* This program is free software; you can redistribute it and/or modify it
6 * under the terms of the license (GNU LGPL) which comes with this package. */
8 #include "JavaContext.hpp"
9 #include "jxbt_utilities.hpp"
10 #include "src/simix/smx_private.hpp"
16 extern "C" JavaVM* __java_vm;
18 XBT_LOG_NEW_DEFAULT_CATEGORY(java, "MSG for Java(TM)");
24 ContextFactory* java_factory()
26 XBT_INFO("Using regular java threads.");
27 return new JavaContextFactory();
30 JavaContextFactory::JavaContextFactory(): ContextFactory("JavaContextFactory")
34 JavaContextFactory::~JavaContextFactory()=default;
36 JavaContext* JavaContextFactory::self()
38 return static_cast<JavaContext*>(xbt_os_thread_get_extra_data());
41 JavaContext* JavaContextFactory::create_context(
42 std::function<void()> code,
43 void_pfn_smxprocess_t cleanup, smx_actor_t process)
45 return this->new_context<JavaContext>(std::move(code), cleanup, process);
48 void JavaContextFactory::run_all()
50 for (smx_actor_t const& process : simgrid::simix::process_get_runnable()) {
51 static_cast<JavaContext*>(process->context)->resume();
55 JavaContext::JavaContext(std::function<void()> code,
56 void_pfn_smxprocess_t cleanup_func,
58 : Context(std::move(code), cleanup_func, process)
60 static int thread_amount=0;
63 /* If the user provided a function for the process then use it otherwise is the context for maestro */
65 this->jprocess = nullptr;
66 this->begin = xbt_os_sem_init(0);
67 this->end = xbt_os_sem_init(0);
70 this->thread = xbt_os_thread_create(
71 nullptr, JavaContext::wrapper, this, nullptr);
75 "Failed to create context #%d. You may want to switch to Java coroutines to increase your limits (error: %s)."
76 "See the Install section of simgrid-java documentation (in doc/install.html) for more on coroutines.",
77 thread_amount, ex.what());
78 xbt_ex new_exception(XBT_THROW_POINT, str);
79 new_exception.category = ex.category;
80 new_exception.value = ex.value;
81 std::throw_with_nested(std::move(new_exception));
84 this->thread = nullptr;
85 xbt_os_thread_set_extra_data(this);
89 JavaContext::~JavaContext()
92 // We are not in maestro context
93 xbt_os_thread_join(this->thread, nullptr);
94 xbt_os_sem_destroy(this->begin);
95 xbt_os_sem_destroy(this->end);
99 void* JavaContext::wrapper(void *data)
101 JavaContext* context = static_cast<JavaContext*>(data);
102 xbt_os_thread_set_extra_data(context);
103 //Attach the thread to the JVM
106 XBT_ATTRIB_UNUSED jint error = __java_vm->AttachCurrentThread((void**)&env, nullptr);
107 xbt_assert((error == JNI_OK), "The thread could not be attached to the JVM");
109 //Wait for the first scheduling round to happen.
110 xbt_os_sem_acquire(context->begin);
111 //Create the "Process" object if needed.
117 void JavaContext::stop()
119 /* I was asked to die (either with kill() or because of a failed element) */
120 if (this->iwannadie) {
122 JNIEnv *env = get_current_thread_env();
123 XBT_DEBUG("Gonna launch Killed Error");
124 // When the process wants to stop before its regular end, we should cut its call stack quickly.
125 // The easiest way to do so is to raise an exception that will be catched in its top calling level.
127 // For that, we raise a ProcessKilledError that is catched in Process::run() (in msg/Process.java)
129 // Throwing a Java exception to stop the actor may be an issue for pure C actors
130 // (as the ones created for the VM migration). The Java exception will not be catched anywhere.
131 // Bad things happen currently if these actors get killed, unfortunately.
132 jxbt_throw_by_name(env, "org/simgrid/msg/ProcessKilledError",
133 std::string("Process ") + this->process()->getCname() + " killed from file JavaContext.cpp");
135 // (remember that throwing a java exception from C does not break the C execution path.
136 // Instead, it marks the exception to be raised when returning to the Java world and
137 // continues to execute the C function until it ends or returns).
139 // Once the Java stack is marked to be unrolled, a C cancel_error is raised to kill the simcall
140 // on which the killed actor is blocked (if any).
141 // Not doing so would prevent the actor to notice that it's dead, leading to segfaults when it wakes up.
142 // This is dangerous: if the killed actor is not actually blocked, the cancel_error will not get catched.
143 // But it should be OK in most cases:
144 // - If I kill myself, I must do so with Process.kill().
145 // The binding of this function in jmsg_process.cpp adds a try/catch around the MSG_process_kill() leading to us
146 // - If I kill someone else that is blocked, the cancel_error will unblock it.
148 // A problem remains probably if I kill a process that is ready_to_run in the same scheduling round.
149 // I guess that this will kill the whole simulation because the victim does not catch the exception.
150 // The only solution I see to that problem would be to completely rewrite the process killing sequence
151 // (also in C) so that it's based on regular C++ exceptions that would be catched anyway.
152 // In other words, we need to do in C++ what we do in Java for sake of uniformity.
154 // Plus, C++ RAII would work in that case, too.
156 XBT_DEBUG("Trigger a cancel error at the C level");
157 THROWF(cancel_error, 0, "process cancelled");
160 /* detach the thread and kills it */
161 JNIEnv *env = this->jenv;
162 env->DeleteGlobalRef(this->jprocess);
163 XBT_ATTRIB_UNUSED jint error = __java_vm->DetachCurrentThread();
164 xbt_assert((error == JNI_OK), "The thread couldn't be detached.");
165 xbt_os_sem_release(this->end);
166 xbt_os_thread_exit(nullptr);
170 void JavaContext::suspend()
172 xbt_os_sem_release(this->end);
173 xbt_os_sem_acquire(this->begin);
176 // FIXME: inline those functions
177 void JavaContext::resume()
179 xbt_os_sem_release(this->begin);
180 xbt_os_sem_acquire(this->end);
183 }}} // namespace simgrid::kernel::context