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")
32 xbt_binary_name = xbt_strdup("java"); // Used by the backtrace displayer
35 JavaContextFactory::~JavaContextFactory()=default;
37 JavaContext* JavaContextFactory::create_context(std::function<void()> code, void_pfn_smxprocess_t cleanup_fun,
40 return this->new_context<JavaContext>(std::move(code), cleanup_fun, actor);
43 void JavaContextFactory::run_all()
45 SerialThreadContext::run_all();
48 JavaContext::JavaContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process)
49 : SerialThreadContext(std::move(code), cleanup_func, process, false /* not maestro */)
51 /* ThreadContext already does all we need */
54 void JavaContext::start_hook()
56 Context::set_current(this); // We need to attach it also for maestro, in contrary to our ancestor
58 //Attach the thread to the JVM
60 XBT_ATTRIB_UNUSED jint error = __java_vm->AttachCurrentThread((void**)&env, nullptr);
61 xbt_assert((error == JNI_OK), "The thread could not be attached to the JVM");
65 void JavaContext::stop()
67 /* I was asked to die (either with kill() or because of a failed element) */
68 if (this->iwannadie) {
70 JNIEnv* env = this->jenv_;
71 XBT_DEBUG("Gonna launch Killed Error");
72 // When the process wants to stop before its regular end, we should cut its call stack quickly.
73 // The easiest way to do so is to raise an exception that will be catched in its top calling level.
75 // For that, we raise a ProcessKilledError that is catched in Process::run() (in msg/Process.java)
77 // Throwing a Java exception to stop the actor may be an issue for pure C actors
78 // (as the ones created for the VM migration). The Java exception will not be catched anywhere.
79 // Bad things happen currently if these actors get killed, unfortunately.
80 jxbt_throw_by_name(env, "org/simgrid/msg/ProcessKilledError",
81 std::string("Process ") + this->process()->get_cname() + " killed from file JavaContext.cpp");
83 // (remember that throwing a java exception from C does not break the C execution path.
84 // Instead, it marks the exception to be raised when returning to the Java world and
85 // continues to execute the C function until it ends or returns).
87 // Once the Java stack is marked to be unrolled, a C cancel_error is raised to kill the simcall
88 // on which the killed actor is blocked (if any).
89 // Not doing so would prevent the actor to notice that it's dead, leading to segfaults when it wakes up.
90 // This is dangerous: if the killed actor is not actually blocked, the cancel_error will not get catched.
91 // But it should be OK in most cases:
92 // - If I kill myself, I must do so with Process.kill().
93 // The binding of this function in jmsg_process.cpp adds a try/catch around the MSG_process_kill() leading to us
94 // - If I kill someone else that is blocked, the cancel_error will unblock it.
96 // A problem remains probably if I kill a process that is ready_to_run in the same scheduling round.
97 // I guess that this will kill the whole simulation because the victim does not catch the exception.
98 // The only solution I see to that problem would be to completely rewrite the process killing sequence
99 // (also in C) so that it's based on regular C++ exceptions that would be catched anyway.
100 // In other words, we need to do in C++ what we do in Java for sake of uniformity.
102 // Plus, C++ RAII would work in that case, too.
103 XBT_DEBUG("Trigger a cancel error at the C level");
104 THROWF(cancel_error, 0, "process cancelled");
106 ThreadContext::stop();
107 JNIEnv* env = this->jenv_;
108 env->DeleteGlobalRef(this->jprocess_);
109 XBT_ATTRIB_UNUSED jint error = __java_vm->DetachCurrentThread();
110 xbt_assert((error == JNI_OK), "The thread couldn't be detached.");
111 xbt_os_thread_exit(nullptr);
115 }}} // namespace simgrid::kernel::context