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Java: Don't detach thread when releasing globals.

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JavaGlobal was unconditionally attaching to (okay) and detaching from (bad)
the current thread during destruction.  We don't want to do this if the
destructor gets called from an attached thread.  Instead, use GetEnv to
first try to get the environment, and only attach and detach if it returns
an error saying the thread is detached.

Also, make sure notifier callbacks appropriately free Java locals to avoid
running out of local variable space.
This commit is contained in:
Peter Johnson
2016-01-01 19:05:00 -08:00
parent 236ef199aa
commit af2f54720d
1 changed files with 30 additions and 17 deletions
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47
java/lib/NetworkTablesJNI.cpp
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@@ -155,12 +155,18 @@ class JavaGlobal {
~JavaGlobal() {
if (!jvm || nt::NotifierDestroyed()) return;
JNIEnv *env;
if (jvm->AttachCurrentThread(reinterpret_cast<void **>(&env), nullptr) !=
JNI_OK)
return;
bool attached = false;
// don't attach and de-attach if already attached to a thread.
if (jvm->GetEnv(reinterpret_cast<void **>(&env), JNI_VERSION_1_6) ==
JNI_EDETACHED) {
if (jvm->AttachCurrentThread(reinterpret_cast<void **>(&env), nullptr) !=
JNI_OK)
return;
attached = true;
}
if (!env || !env->functions) return;
env->DeleteGlobalRef(m_obj);
jvm->DetachCurrentThread();
if (attached) jvm->DetachCurrentThread();
}
operator T() { return m_obj; }
T obj() { return m_obj; }
@@ -180,12 +186,18 @@ class JavaWeakGlobal {
~JavaWeakGlobal() {
if (!jvm || nt::NotifierDestroyed()) return;
JNIEnv *env;
if (jvm->AttachCurrentThread(reinterpret_cast<void **>(&env), nullptr) !=
JNI_OK)
return;
bool attached = false;
// don't attach and de-attach if already attached to a thread.
if (jvm->GetEnv(reinterpret_cast<void **>(&env), JNI_VERSION_1_6) ==
JNI_EDETACHED) {
if (jvm->AttachCurrentThread(reinterpret_cast<void **>(&env), nullptr) !=
JNI_OK)
return;
attached = true;
}
if (!env || !env->functions) return;
env->DeleteWeakGlobalRef(m_obj);
jvm->DetachCurrentThread();
if (attached) jvm->DetachCurrentThread();
}
JavaLocal<T> obj(JNIEnv *env) {
return JavaLocal<T>(env, env->NewLocalRef(m_obj));
@@ -1001,16 +1013,17 @@ JNIEXPORT jint JNICALL Java_edu_wpi_first_wpilibj_networktables_NetworkTablesJNI
auto handler = listener_global->obj();
// convert the value into the appropriate Java type
jobject jobj = ToJavaObject(env, *value);
if (!jobj) return;
JavaLocal<jobject> jobj(env, ToJavaObject(env, *value));
if (env->ExceptionCheck()) {
env->ExceptionDescribe();
env->ExceptionClear();
return;
}
env->CallVoidMethod(handler, mid, (jint)uid, ToJavaString(env, name),
jobj, (jint)(flags_));
if (!jobj) return;
JavaLocal<jstring> jname(env, ToJavaString(env, name));
env->CallVoidMethod(handler, mid, (jint)uid, jname.obj(), jobj.obj(),
(jint)(flags_));
if (env->ExceptionCheck()) {
env->ExceptionDescribe();
env->ExceptionClear();
@@ -1062,16 +1075,16 @@ JNIEXPORT jint JNICALL Java_edu_wpi_first_wpilibj_networktables_NetworkTablesJNI
//if (!handler) goto done; // can happen due to weak reference
// convert into the appropriate Java type
jobject jobj = ToJavaObject(env, conn);
if (!jobj) return;
JavaLocal<jobject> jobj(env, ToJavaObject(env, conn));
if (env->ExceptionCheck()) {
env->ExceptionDescribe();
env->ExceptionClear();
return;
}
if (!jobj) return;
env->CallVoidMethod(handler, mid, (jint)uid,
(jboolean)(connected ? 1 : 0), jobj);
(jboolean)(connected ? 1 : 0), jobj.obj());
if (env->ExceptionCheck()) {
env->ExceptionDescribe();
env->ExceptionClear();