ndk/looper: Deprecate poll_all*() and document implied wake results
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[Upstream clarified] that due to limitations in `ALooper`, the `poll*()` functions may not be able to distinguish an explicit `wake()` call from any other wakeup source, including callbacks, timeouts, fd events or even errors. Any return value from these functions should be treated as if a `Poll::Wake` event is also returned. While this is not only problematic to tell a wake apart from other events, it makes it impossible for the `poll_all*()` variants to return correctly as they will keep looping internally on callbacks (which are subsuming a wake event). According to [upstream `ALooper_pollAll()` documentation] this is considered "not safe" and the function is no longer allowed to be called. [Upstream clarified]: android/ndk#2020 [upstream `ALooper_pollAll()` documentation]: https://developer.android.com/ndk/reference/group/looper#alooper_pollall
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Upstream clarified that due to limitations in
ALooper, thepoll*()functions may not be able to distinguish an explicitwake()call from any other wakeup source, including callbacks, timeouts, fd events or even errors. Any return value from these functions should be treated as if aPoll::Wakeevent is also returned.While this is not only problematic to tell a wake apart from other events, it makes it impossible for the
poll_all*()variants to return correctly as they will keep looping internally on callbacks (which are subsuming a wake event). According to upstreamALooper_pollAll()documentation this is considered "not safe" and the function is no longer allowed to be called.