ndk/media/image_reader: Don't assume ownership of NativeWindow
#418
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When implementing proper ownership `acquire()` and `release()` semantics for `NativeWindow` in #207, I thought I had checked all existing calls to `NativeWindow::from_ptr()` to make sure that they return a pointer that we get ownership over, and have to clean up ourselves. This turns out to [not be the case for `AImageReader_getWindow()`]: The ANativeWindow is managed by this image reader. Do NOT call ANativeWindow_release on it. Instead, use AImageReader_delete. And can be trivially reproduced by creating an `ImageReader` and calling `.get_window()`. Dropping the `NativeWindow` is fine but subsequently dropping the `ImageReader` results in a NULL-pointer SEGFAULT. For now calling `clone_from_ptr()` is enough to first acquire an extra reference on the pointer so that ownership remains balanced, but in the future we'd like to investigate a [new non-owned `NativeWindow` type similar to `HardwareBuffer`]. As of writing the following calls to `from_ptr()` remain, that are all confirmed to transfer ownership and require cleanup via `_release()`: - `ASurfaceTexture_acquireANativeWindow()`; - `AMediaCodec_createInputSurface()`; - `AMediaCodec_createPersistentInputSurface()`; - `ANativeWindow_fromSurface()`. [not be the case for `AImageReader_getWindow()`]: https://developer.android.com/ndk/reference/group/media#aimagereader_getwindow [new non-owned `NativeWindow` type similar to `HardwareBuffer`]: #309
rib
approved these changes
Aug 15, 2023
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Yup, should be enough asserts there. |
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When implementing proper ownership
acquire()andrelease()semantics forNativeWindowin #207, I thought I had checked all existing calls toNativeWindow::from_ptr()to make sure that they return a pointer that we get ownership over, and have to clean up ourselves. This turns out to not be the case forAImageReader_getWindow():And can be trivially reproduced by creating an
ImageReaderand calling.get_window(). Dropping theNativeWindowis fine but subsequently dropping theImageReaderresults in a NULL-pointer SEGFAULT.For now calling
clone_from_ptr()is enough to first acquire an extra reference on the pointer so that ownership remains balanced, but in the future we'd like to investigate a new non-ownedNativeWindowtype similar toHardwareBuffer.As of writing the following calls to
from_ptr()remain, that are all confirmed to transfer ownership and require cleanup via_release():ASurfaceTexture_acquireANativeWindow();AMediaCodec_createInputSurface();AMediaCodec_createPersistentInputSurface();ANativeWindow_fromSurface().