JNI warnings in TryXShmAttach

Run netbeans 7.3.1 with -Xcheck:jni. With JDK 7u40, only a few, seemingly harmless warnings are printed. With JDK8 b106, a large number of warnings are printed:

Warning: Calling other JNI functions in the scope of Get/ReleasePrimitiveArrayCritical or Get/ReleaseStringCritical
Warning: Calling other JNI functions in the scope of Get/ReleasePrimitiveArrayCritical or Get/ReleaseStringCritical
Warning: Calling other JNI functions in the scope of Get/ReleasePrimitiveArrayCritical or Get/ReleaseStringCritical
Warning: Calling other JNI functions in the scope of Get/ReleasePrimitiveArrayCritical or Get/ReleaseStringCritical
...

The JNI functions that cause these warnings are Java_sun_java2d_loops_Blit_Blit and Java_sun_java2d_loops_MaskBlit_MaskBlit. They are trying to copy a source image (in memory buffer) to a destination image (in X11).

[1] It first calls BufImg_GetRasInfo, which calls jni_GetPrimitiveArrayCritical, which calls GC_locker::jni_lock to prevent GC from happening.

[2] Then, it calls X11SD_GetRasInfo, which tries to execute a Java method:

    #0 functionEnter (thr=0x7f69e4170800) at src/share/vm/prims/jniCheck.cpp:187
    #1 0x00007f6a6b987b3c in checked_jni_EnsureLocalCapacity (env=0x7f69e4170a20, capacity=3)
    #2 0x00007f6a6aa934ac in JNU_CallStaticMethodByName ()
    #3 0x00007f6a44d4113f in TryXShmAttach ()
    #4 0x00007f6a44d32825 in X11SD_CreateSharedImage ()
    #5 0x00007f6a44d33eb4 in X11SD_GetImage ()
    #6 0x00007f6a44d3464a in X11SD_GetRasInfo ()
    #7 0x00007f6a45062ee1 in Java_sun_java2d_loops_Blit_Blit ()

Actually a few different methods are called while the primitive array is still being held.

If one of these Java methods causes a GC, we will deadlock because GC has been disabled.

The chance for deadlock may be higher for apps which refreshes the screen frequently and creates a lot of garbage.