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Android: change the way JNIEnv is retrieved

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- Currently, it tries to Attach the JVM first and update the thread local storage, which are two operations.
  Now, it simply gives back the JNI Env stored for the thread.

- Android_JNI_SetupThreadi() should only be used for external.
  For internal SDL thread, it's already called in RunThread() (SDL_systhread.c),
  and other thread are Java threads which don't need to be attached. i
  (even if it doesn't hurt to do it, since it's a no-op).

- JNI_OnLoad is filled with pthread_create, GetEnv, AttachCurrentThread...
  It's called for all shared libraries which may don't want this setup,
  and loading libraries can be also modified to be done from a static context,
  or with relinker. So it's not really clear how, who and what it sets up.
  => Reduce this function to the minimal
This commit is contained in:
Sylvain Becker 2019-01-11 21:42:52 +01:00
parent dc10d96cde
commit 7f3478305f
1 changed files with 50 additions and 31 deletions
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81
src/core/android/SDL_android.c
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@ -294,7 +294,7 @@ static SDL_bool bHasNewData;
static SDL_bool bHasEnvironmentVariables = SDL_FALSE;
static void Android_JNI_SetEnv(JNIEnv *env);
static int Android_JNI_SetEnv(JNIEnv *env);
/*******************************************************************************
Functions called by JNI
@ -321,21 +321,7 @@ Android_JNI_CreateKey_once()
/* Library init */
JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved)
{
JNIEnv *env;
mJavaVM = vm;
LOGI("JNI_OnLoad called");
if ((*mJavaVM)->GetEnv(mJavaVM, (void **) &env, JNI_VERSION_1_4) != JNI_OK) {
LOGE("Failed to get the environment using GetEnv()");
return -1;
}
/*
* Create mThreadKey so we can keep track of the JNIEnv assigned to each thread
* Refer to http://developer.android.com/guide/practices/design/jni.html for the rationale behind this
*/
Android_JNI_CreateKey_once();
Android_JNI_SetupThread();
return JNI_VERSION_1_4;
}
@ -354,6 +340,19 @@ JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeSetupJNI)(JNIEnv *env, jclass cl
{
__android_log_print(ANDROID_LOG_VERBOSE, "SDL", "nativeSetupJNI()");
/*
* Create mThreadKey so we can keep track of the JNIEnv assigned to each thread
* Refer to http://developer.android.com/guide/practices/design/jni.html for the rationale behind this
*/
Android_JNI_CreateKey_once();
/* Save JNIEnv of SDLActivity */
Android_JNI_SetEnv(env);
if (mJavaVM == NULL) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "failed to found a JavaVM");
}
/* Use a mutex to prevent concurrency issues between Java Activity and Native thread code, when using 'Android_Window'.
* (Eg. Java sending Touch events, while native code is destroying the main SDL_Window. )
*/
@ -365,8 +364,6 @@ JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeSetupJNI)(JNIEnv *env, jclass cl
__android_log_print(ANDROID_LOG_ERROR, "SDL", "failed to create Android_ActivityMutex mutex");
}
Android_JNI_SetupThread();
mActivityClass = (jclass)((*env)->NewGlobalRef(env, cls));
midGetNativeSurface = (*env)->GetStaticMethodID(env, mActivityClass,
@ -444,8 +441,6 @@ JNIEXPORT void JNICALL SDL_JAVA_AUDIO_INTERFACE(nativeSetupJNI)(JNIEnv *env, jcl
{
__android_log_print(ANDROID_LOG_VERBOSE, "SDL", "AUDIO nativeSetupJNI()");
Android_JNI_SetupThread();
mAudioManagerClass = (jclass)((*env)->NewGlobalRef(env, cls));
midAudioOpen = (*env)->GetStaticMethodID(env, mAudioManagerClass,
@ -484,8 +479,6 @@ JNIEXPORT void JNICALL SDL_JAVA_CONTROLLER_INTERFACE(nativeSetupJNI)(JNIEnv *env
{
__android_log_print(ANDROID_LOG_VERBOSE, "SDL", "CONTROLLER nativeSetupJNI()");
Android_JNI_SetupThread();
mControllerManagerClass = (jclass)((*env)->NewGlobalRef(env, cls));
midPollInputDevices = (*env)->GetStaticMethodID(env, mControllerManagerClass,
@ -516,6 +509,9 @@ JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(JNIEnv *env, jclass cls,
__android_log_print(ANDROID_LOG_VERBOSE, "SDL", "nativeRunMain()");
/* Save JNIEnv of SDLThread */
Android_JNI_SetEnv(env);
library_file = (*env)->GetStringUTFChars(env, library, NULL);
library_handle = dlopen(library_file, RTLD_GLOBAL);
if (library_handle) {
@ -1155,11 +1151,12 @@ static void Android_JNI_ThreadDestroyed(void *value)
}
}
static void Android_JNI_SetEnv(JNIEnv *env) {
static int Android_JNI_SetEnv(JNIEnv *env) {
int status = pthread_setspecific(mThreadKey, env);
if (status < 0) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed pthread_setspecific() in Android_JNI_SetEnv() (err=%d)", status);
}
return status;
}
JNIEnv* Android_JNI_GetEnv(void)
@ -1176,13 +1173,6 @@ JNIEnv* Android_JNI_GetEnv(void)
* Note: You can call this function any number of times for the same thread, there's no harm in it
*/
JNIEnv *env;
int status = (*mJavaVM)->AttachCurrentThread(mJavaVM, &env, NULL);
if (status < 0) {
LOGE("failed to attach current thread");
return 0;
}
/* From http://developer.android.com/guide/practices/jni.html
* Threads attached through JNI must call DetachCurrentThread before they exit. If coding this directly is awkward,
* in Android 2.0 (Eclair) and higher you can use pthread_key_create to define a destructor function that will be
@ -1192,14 +1182,43 @@ JNIEnv* Android_JNI_GetEnv(void)
* Note: You can call this function any number of times for the same thread, there's no harm in it
* (except for some lost CPU cycles)
*/
Android_JNI_SetEnv(env);
/* Get JNIEnv from the Thread local storage */
JNIEnv *env = pthread_getspecific(mThreadKey);
if (env == NULL) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "JNIEnv is NULL. Call Android_JNI_SetupThread() first.");
}
return env;
}
int Android_JNI_SetupThread(void)
{
Android_JNI_GetEnv();
JNIEnv *env;
int status;
/* There should be a JVM */
if (mJavaVM == NULL) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed, there is no JavaVM");
return 0;
}
/* Attach the current thread to the JVM and get a JNIEnv.
* It will be detached by pthread_create destructor 'Android_JNI_ThreadDestroyed'
*/
status = (*mJavaVM)->AttachCurrentThread(mJavaVM, &env, NULL);
if (status < 0) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed to attach current thread (err=%d)", status);
return 0;
}
/* Save JNIEnv into the Thread local storage */
if (Android_JNI_SetEnv(env) < 0) {
return 0;
}
return 1;
}