JNI thread management issue

mfkl commented 5 years ago

Hi,

I am using libvlc in a Xamarin.Android application and get a reproducible native crash.

I'm not 100% sure, but it looks like mono makes assumptions regarding JNI interactions in this code: https://github.com/xamarin/xamarin-android/blob/c474d4c82330c4b13ecc21a9e16a9d66b329611c/src/monodroid/jni/monodroid-glue.cc#L339-L369

VLC has similar code:

         /* if GetEnv returns JNI_OK, the thread is already attached to the
         * JavaVM, so we are already in a java thread, and we don't have to
         * setup any destroy callbacks */
        if ((*jvm)->GetEnv(jvm, (void **)&env, JNI_VERSION_1_2) != JNI_OK)
        {
            /* attach the thread to the Java VM */
            JavaVMAttachArgs args;

            args.version = JNI_VERSION_1_2;
            args.name = psz_name;
            args.group = NULL;

            if ((*jvm)->AttachCurrentThread(jvm, &env, &args) != JNI_OK)
                return NULL;

            /* Set the attached env to the thread-specific data area (TSD) */
            if (pthread_setspecific(jni_env_key, env) != 0)
            {
                (*jvm)->DetachCurrentThread(jvm);
                return NULL;
            }
        }

https://github.com/videolan/vlc-3.0/blob/264d5a9ec1bc1b2e4d9defa6be49cf7ef39a2984/modules/video_output/android/utils.c#L374-L395

Steps to Reproduce

https://code.videolan.org/videolan/LibVLCSharp/issues/123
Run the vout sample from https://github.com/kakone/libvlcsharp_samples/tree/master/Samples/Samples

Expected Behavior

No crash.

Actual Behavior

Crash because mono calls DetachCurrentThread on a thread it doesn't own.

Version Information

Microsoft Visual Studio Community 2017 Version 15.9.9 VisualStudio.15.Release/15.9.9+28307.518 Microsoft .NET Framework Version 4.7.03056

Installed Version: Community

Visual C++ 2017 00369-60000-00001-AA760 Microsoft Visual C++ 2017

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Log File

https://gist.github.com/mfkl/17438043c0b721f3054b2daa0f6334e4

mfkl commented 4 years ago

Hello,

This appears to still be an issue. How can I help move this forward?

DarthMouayed commented 1 year ago

So frustrating 😔, this issue is preventing me from using hardware acceleration in LibVlcSharp.

dotnet / android