JavaKit: Passing objects between threads

[lhoward]

javaMethodLookup() uses the environment attached to the object, probably it should use the ambient (thread-specific) environment or the one that is passed in?

java_vm_ext.cc:599] JNI DETECTED ERROR IN APPLICATION: thread Thread[23,tid=1783,Native,Thread*=0xb40000718be7eb40,peer=0x1449d000,"Thread-4"] using JNIEnv* from thread Thread[1,tid=1631,Native,Thread*=0xb40000718be307b0,peer=0x72c1eb68,"main"]
                                                                                                    java_vm_ext.cc:599]     in call to GetObjectClass

From the JNI specs:

The JNI interface pointer is only valid in the current thread. A native method, therefore, must not pass the interface pointer from one thread to another. A VM implementing the JNI may allocate and store thread-local data in the area pointed to by the JNI interface pointer.

So, I think this is a bug. Is the fix as simple as adding an environment argument to javaMethodLookup()?

[lhoward]

It's not a huge issue because I can schedule things on the main thread but, would be nice to not need to do this (to avoid excess context switches).

[lhoward]

I just did this for now – PADL@c3f2314 – but obviously it's a workaround. I think I need upstream input as to what the right solution is, whether we remove javaEnvironment completely and always use the ambient environment. cc @DougGregor