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