1 /* Context switching within the JVM. */
3 /* Copyright (c) 2009-2018. 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 "simgrid/Exception.hpp"
11 #include "src/simix/smx_private.hpp"
16 extern 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(std::function<void()> code, void_pfn_smxprocess_t cleanup_fun,
44 return this->new_context<JavaContext>(std::move(code), cleanup_fun, actor);
47 void JavaContextFactory::run_all()
49 for (smx_actor_t const& process : simgrid::simix::process_get_runnable()) {
50 static_cast<JavaContext*>(process->context_)->resume();
54 JavaContext::JavaContext(std::function<void()> code,
55 void_pfn_smxprocess_t cleanup_func,
57 : Context(std::move(code), cleanup_func, process)
59 /* If the user provided a function for the process then use it. Otherwise is the context for maestro */
61 this->begin_ = xbt_os_sem_init(0);
62 this->end_ = xbt_os_sem_init(0);
64 this->thread_ = xbt_os_thread_create(nullptr, JavaContext::wrapper, this, nullptr);
66 xbt_os_thread_set_extra_data(this);
70 JavaContext::~JavaContext()
73 // We are not in maestro context
74 xbt_os_thread_join(this->thread_, nullptr);
75 xbt_os_sem_destroy(this->begin_);
76 xbt_os_sem_destroy(this->end_);
80 void* JavaContext::wrapper(void *data)
82 JavaContext* context = static_cast<JavaContext*>(data);
83 xbt_os_thread_set_extra_data(context);
84 //Attach the thread to the JVM
87 XBT_ATTRIB_UNUSED jint error = __java_vm->AttachCurrentThread((void**)&env, nullptr);
88 xbt_assert((error == JNI_OK), "The thread could not be attached to the JVM");
90 //Wait for the first scheduling round to happen.
91 xbt_os_sem_acquire(context->begin_);
92 //Create the "Process" object if needed.
98 void JavaContext::stop()
100 /* I was asked to die (either with kill() or because of a failed element) */
101 if (this->iwannadie) {
103 JNIEnv *env = get_current_thread_env();
104 XBT_DEBUG("Gonna launch Killed Error");
105 // When the process wants to stop before its regular end, we should cut its call stack quickly.
106 // The easiest way to do so is to raise an exception that will be catched in its top calling level.
108 // For that, we raise a ProcessKilledError that is catched in Process::run() (in msg/Process.java)
110 // Throwing a Java exception to stop the actor may be an issue for pure C actors
111 // (as the ones created for the VM migration). The Java exception will not be catched anywhere.
112 // Bad things happen currently if these actors get killed, unfortunately.
113 jxbt_throw_by_name(env, "org/simgrid/msg/ProcessKilledError",
114 std::string("Process ") + this->process()->get_cname() + " killed from file JavaContext.cpp");
116 // (remember that throwing a java exception from C does not break the C execution path.
117 // Instead, it marks the exception to be raised when returning to the Java world and
118 // continues to execute the C function until it ends or returns).
120 // Once the Java stack is marked to be unrolled, a C cancel_error is raised to kill the simcall
121 // on which the killed actor is blocked (if any).
122 // Not doing so would prevent the actor to notice that it's dead, leading to segfaults when it wakes up.
123 // This is dangerous: if the killed actor is not actually blocked, the cancel_error will not get catched.
124 // But it should be OK in most cases:
125 // - If I kill myself, I must do so with Process.kill().
126 // The binding of this function in jmsg_process.cpp adds a try/catch around the MSG_process_kill() leading to us
127 // - If I kill someone else that is blocked, the cancel_error will unblock it.
129 // A problem remains probably if I kill a process that is ready_to_run in the same scheduling round.
130 // I guess that this will kill the whole simulation because the victim does not catch the exception.
131 // The only solution I see to that problem would be to completely rewrite the process killing sequence
132 // (also in C) so that it's based on regular C++ exceptions that would be catched anyway.
133 // In other words, we need to do in C++ what we do in Java for sake of uniformity.
135 // Plus, C++ RAII would work in that case, too.
137 XBT_DEBUG("Trigger a cancel error at the C level");
138 THROWF(cancel_error, 0, "process cancelled");
141 /* detach the thread and kills it */
142 JNIEnv* env = this->jenv_;
143 env->DeleteGlobalRef(this->jprocess_);
144 XBT_ATTRIB_UNUSED jint error = __java_vm->DetachCurrentThread();
145 xbt_assert((error == JNI_OK), "The thread couldn't be detached.");
146 xbt_os_sem_release(this->end_);
147 xbt_os_thread_exit(nullptr);
151 void JavaContext::suspend()
153 xbt_os_sem_release(this->end_);
154 xbt_os_sem_acquire(this->begin_);
157 // FIXME: inline those functions
158 void JavaContext::resume()
160 xbt_os_sem_release(this->begin_);
161 xbt_os_sem_acquire(this->end_);
164 }}} // namespace simgrid::kernel::context