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. */
11 #include "JavaContext.hpp"
12 #include "jxbt_utilities.h"
13 #include "src/simix/smx_private.h"
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 xbt_dynar_t processes = SIMIX_process_get_runnable();
53 xbt_dynar_foreach(processes, cursor, process) {
54 static_cast<JavaContext*>(SIMIX_process_get_context(process))->resume();
58 JavaContext::JavaContext(std::function<void()> code,
59 void_pfn_smxprocess_t cleanup_func,
61 : Context(std::move(code), cleanup_func, process)
63 static int thread_amount=0;
66 /* If the user provided a function for the process then use it otherwise is the context for maestro */
68 this->jprocess = nullptr;
69 this->begin = xbt_os_sem_init(0);
70 this->end = xbt_os_sem_init(0);
73 this->thread = xbt_os_thread_create(
74 nullptr, JavaContext::wrapper, this, nullptr);
78 "Failed to create context #%d. You may want to switch to Java coroutines to increase your limits (error: %s)."
79 "See the Install section of simgrid-java documentation (in doc/install.html) for more on coroutines.",
80 thread_amount, ex.what());
81 xbt_ex new_exception(XBT_THROW_POINT, str);
82 new_exception.category = ex.category;
83 new_exception.value = ex.value;
84 std::throw_with_nested(std::move(new_exception));
87 this->thread = nullptr;
88 xbt_os_thread_set_extra_data(this);
92 JavaContext::~JavaContext()
95 // We are not in maestro context
96 xbt_os_thread_join(this->thread, nullptr);
97 xbt_os_sem_destroy(this->begin);
98 xbt_os_sem_destroy(this->end);
102 void* JavaContext::wrapper(void *data)
104 JavaContext* context = static_cast<JavaContext*>(data);
105 xbt_os_thread_set_extra_data(context);
106 //Attach the thread to the JVM
109 XBT_ATTRIB_UNUSED jint error = __java_vm->AttachCurrentThread((void**)&env, nullptr);
110 xbt_assert((error == JNI_OK), "The thread could not be attached to the JVM");
112 //Wait for the first scheduling round to happen.
113 xbt_os_sem_acquire(context->begin);
114 //Create the "Process" object if needed.
120 void JavaContext::stop()
122 /* I was asked to die (either with kill() or because of a failed element) */
123 if (this->iwannadie) {
125 JNIEnv *env = get_current_thread_env();
126 XBT_DEBUG("Gonna launch Killed Error");
127 // When the process wants to stop before its regular end, we should cut its call stack quickly.
128 // The easiest way to do so is to raise an exception that will be catched in its top calling level.
130 // For that, we raise a ProcessKilledError that is catched in Process::run() (in msg/Process.java)
132 // Throwing a Java exception to stop the actor may be an issue for pure C actors
133 // (as the ones created for the VM migration). The Java exception will not be catched anywhere.
134 // Bad things happen currently if these actors get killed, unfortunately.
135 jxbt_throw_by_name(env, "org/simgrid/msg/ProcessKilledError",
136 bprintf("Process %s killed from file JavaContext.cpp)", this->process()->name.c_str()));
138 // (remember that throwing a java exception from C does not break the C execution path.
139 // Instead, it marks the exception to be raised when returning to the Java world and
140 // continues to execute the C function until it ends or returns).
142 // Once the Java stack is marked to be unrolled, a C cancel_error is raised to kill the simcall
143 // on which the killed actor is blocked (if any).
144 // Not doing so would prevent the actor to notice that it's dead, leading to segfaults when it wakes up.
145 // This is dangerous: if the killed actor is not actually blocked, the cancel_error will not get catched.
146 // But it should be OK in most cases:
147 // - If I kill myself, I must do so with Process.kill().
148 // The binding of this function in jmsg_process.cpp adds a try/catch around the MSG_process_kill() leading to us
149 // - If I kill someone else that is blocked, the cancel_error will unblock it.
151 // A problem remains probably if I kill a process that is ready_to_run in the same scheduling round.
152 // I guess that this will kill the whole simulation because the victim does not catch the exception.
153 // The only solution I see to that problem would be to completely rewrite the process killing sequence
154 // (also in C) so that it's based on regular C++ exceptions that would be catched anyway.
155 // In other words, we need to do in C++ what we do in Java for sake of uniformity.
157 // Plus, C++ RAII would work in that case, too.
159 XBT_DEBUG("Trigger a cancel error at the C level");
160 THROWF(cancel_error, 0, "process cancelled");
163 /* detach the thread and kills it */
164 JNIEnv *env = this->jenv;
165 env->DeleteGlobalRef(this->jprocess);
166 XBT_ATTRIB_UNUSED jint error = __java_vm->DetachCurrentThread();
167 xbt_assert((error == JNI_OK), "The thread couldn't be detached.");
168 xbt_os_sem_release(this->end);
169 xbt_os_thread_exit(nullptr);
173 void JavaContext::suspend()
175 xbt_os_sem_release(this->end);
176 xbt_os_sem_acquire(this->begin);
179 // FIXME: inline those functions
180 void JavaContext::resume()
182 xbt_os_sem_release(this->begin);
183 xbt_os_sem_acquire(this->end);
186 }}} // namespace simgrid::kernel::context