miniaudio: bound the OpenSL ES buffer-queue drain - #19
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ma_device_drain__opensl() spins in an unbounded for(;;)/ma_sleep(10) loop until the buffer queue reports empty, with no timeout and no iteration cap. If the OpenSL callback thread stops servicing the queue -- audioserver hiccup, route change, device disconnect -- the count never reaches zero and ma_device_stop() never returns (alnitak#333). Since the audio device is stopped on every idle timeout to release the audioserver AudioMix partial wakelock, that is an unrecoverable hang on a routine path. miniaudio itself disabled the equivalent stop inside ma_device_uninit() for the same reason; see its "can result in a deadlock" comment there. The queue can only legitimately hold `periods` buffers of `periodSizeInFrames`, so the wait is capped at twice that duration, clamped to [200ms, 1000ms]. Bailing out is safe: both callers in ma_device_stop__opensl() immediately follow the drain with SetPlayState(SL_PLAYSTATE_STOPPED) and Clear() on the same queue, so the worst case is discarding a few milliseconds of tail audio that Clear() was going to discard anyway. This is a local patch to vendored miniaudio 0.11.25, marked with a greppable banner. It should be carried across miniaudio updates, and is worth reporting upstream: the loop is unbounded for every OpenSL user. Verified without an NDK (the backend is __ANDROID__-only) by exercising the added arithmetic against the real ma_device struct (4096x3@48k -> 512ms, 512x3@48k -> 200ms floor, 8192x4@44k -> 1000ms ceiling, 0x0@0 -> no divide by zero, UINT32_MAX x8 -> no 32-bit overflow), compiling the patched function verbatim against OpenSL stubs under C99 and C89 with -Wall -Wextra, and running a stalled-queue harness: the unpatched function loops forever (killed at 5s), the patched one returns after ~520ms matching the bound. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Summary
Upstream miniaudio waits indefinitely for the OpenSL ES buffer queue to report empty. If the callback queue stalls,
ma_device_stop()can block indefinitely; flutter_soloud now calls device stop routinely for idle stopping.Approach
deviceTypeargument for queue, timing, and draining-flag selection, so duplex devices drain capture and playback independently.GetState()and ends the drain attempt on failure without inspecting queue state.Verification
git diff --checkflutter pub getflutter analyze(passed; six informational lints reported in existing example tests)flutter test(passed)cd example && flutter build apk --debugwas attempted, but the build could not proceed because the example configures NDK 27.0.12077973 while dependencyjnirequires NDK 28.2.13676358. No Android/NDK compile result is claimed.Maintenance note
The
flutter_soloud local patchmarkers must be preserved when updating vendored miniaudio.