ndk-glue: Don't return from onCreate until LOOPER is created #131
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Android only performs additional initialization like providing an input queue through `onInputQueueCreated` after the main initialization function (`ANativeActivity_onCreate`) returns. In some cases it is possible that the main thread spawned here hasn't attached a looper to its thread and assigned it to the accompanying `LOOPER` static variable yet, resulting in a `None` unwrap when Android provides us with an input queue. This race condition is simply solved by not returning from `fn init()` (`ANativeActivity_onCreate`) until the thread has finished its setup, through wrapping `LOOPER` in a `Mutex` and using a condition variable to signal when it is ready. This condition is intentionally not exposed to `on_input_queue_created` may we ever have a cleanup procedure that sets `LOOPER` back to `None`; any call to `onInputQueueCreated` in that state would be an error and should not block indefinitely. The `LOOPER` should simply be ready by the time `fn init()` returns. Fixes rust-mobile#116
MarijnS95
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@MarijnS95 Thank you! Tested this patch in my case. Works well. |
msiglreith
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Mar 20, 2021
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Android only performs additional initialization like providing an input queue through
onInputQueueCreatedafter the main initialization function (ANativeActivity_onCreate) returns. In some cases it is possible that the main thread spawned here hasn't attached a looper to its thread and assigned it to the accompanyingLOOPERstatic variable yet, resulting in aNoneunwrap when Android provides us with an input queue.This race condition is simply solved by not returning from
fn init()(ANativeActivity_onCreate) until the thread has finished its setup, through wrappingLOOPERin aMutexand using a condition variable to signal when it is ready.This condition is intentionally not exposed to
on_input_queue_createdmay we ever have a cleanup procedure that setsLOOPERback toNone; any call toonInputQueueCreatedin that state would be an error and should not block indefinitely. TheLOOPERshould simply be ready by the timefn init()returns.Fixes #116
CC @Gordon-F