Question

I have some JNI code in a thread that calls from Java to C. The code works but if I put too much pressure on it (execute too many instructions), it will crash:

W/dalvikvm( 1502): JNI local reference table summary (512 entries):
W/dalvikvm( 1502):   512 of Ljava/lang/Class; 164B (1 unique)
W/dalvikvm( 1502): Memory held directly by tracked refs is 164 bytes
E/dalvikvm( 1502): Failed adding to JNI local ref table (has 512 entries)
I/dalvikvm( 1502): "Thread-17" prio=5 tid=10 RUNNABLE
I/dalvikvm( 1502):   | group="main" sCount=0 dsCount=0 s=N obj=0x40114910 self=0xd3d40
I/dalvikvm( 1502):   | sysTid=1542 nice=0 sched=0/0 cgrp=default handle=821104
I/dalvikvm( 1502):   | schedstat=( 359863282 630188006 2660 )
I/dalvikvm( 1502):   at dalvik.system.NativeStart.run(Native Method)
I/dalvikvm( 1502): 
E/dalvikvm( 1502): VM aborting
I/DEBUG   ( 1011): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
I/DEBUG   ( 1011): Build fingerprint: 'verizon/voles/sholes/sholes:2.2.2/FRG83G/91102:user/release-keys'
I/DEBUG   ( 1011): pid: 1502, tid: 1542  >>> app_process <<<
I/DEBUG   ( 1011): signal 11 (SIGSEGV), fault addr deadd00d
I/DEBUG   ( 1011):  r0 00000026  r1 afd14629  r2 afd14629  r3 00000000
I/DEBUG   ( 1011):  r4 805a23f4  r5 805a23f4  r6 000d3d40  r7 000d3d90
I/DEBUG   ( 1011):  r8 00100000  r9 80601f45  10 449f1000  fp 4453ed90
I/DEBUG   ( 1011):  ip deadd00d  sp 44af0dc0  lr afd15673  pc 805420b8  cpsr 20000030

In my call from Java to C, I keep a GlobalReference to the class I want to call and then create a new thread:

JNIEXPORT void JNICALL Java_com_device_client_HostConnection_initialize
(JNIEnv * env, jobject obj, jobject inject)
{
    JavaVM *tmpVM;
    jint result = env->GetJavaVM(&tmpVM);
    if (result < 0) {
        LOGE("Error using GetJavaVM\n");
        exit(-1);
    }

    jobject tmpHostObject = env->NewGlobalRef(inject);
    if (tmpHostObject == NULL) {
        LOGE("ERROR: Run out of memory for weak global ref\n");
        exit(-1);
    }

    vm = tmpVM;
    hostObject = tmpHostObject;

    pthread_t pth;
    pthread_create(&pth, NULL, startServer, NULL);
    pthread_join(pth, NULL);
}

Here vm and hostObject are global variables. In my new thread, I call a Java method from the inject object that I passed along and created a GobalRef to:

void *startServer(void* arg)
{
    JNIEnv* env = NULL;
    jmethodID mid;
    jclass hostClass;

    vm->AttachCurrentThread(&env, NULL);

    while (run) {
        /* some code */

        /* Calls a new thread */
        pthread_t pth;
        pthread_create(&pth, NULL, receive, NULL);

        /* more code */
    }
    vm->DetachCurrentThread();
}

void *receive()
{
    jmethodID mid;
    jclass hostClass;
    JNIEnv* env = NULL;

    vm->AttachCurrentThread(&env, NULL)

    while (1) {
        /* receive x, y and action */

        hostClass = env->GetObjectClass(hostObject);
        mid = env->GetMethodID(hostClass, "executeTouch", "(III)V");
        if (mid == 0) {
            LOGD("ERROR: GetMethodID\n");
            exit(-1);
        }
        env->CallVoidMethod(hostObject, mid, x * 2, y * 2, action);
    }

    vm->DetachCurrentThread();
}

Does anyone please know what is going on? I am running out of memory please? Why would that be and how could I please avoid it?

EDIT:

I realized that I didn’t need to get the MethodID all the time, I could just store it locally before the while (1). This fixed my problem! Sorry for the issue, thanks.

Thank you very much.

Answer 1

I realized that I didn’t need to get the MethodID all the time, I could just store it locally before the while (1). This fixed my problem! Sorry for the issue, thanks.