wasm: Avoid blocking the browser main thread#174
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When using flume with Wasm in the browser, and without the spin feature, blocking when attempting to lock a mutex which is already locked on the main thread will panic and thereby crash the application. To resolve the issue, use a spinlock on the browser main thread, through the `wasm_safe_mutex` crate. Web worker threads will continue to sleep when locking a mutex as usual.
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When using flume with Wasm in the browser, and without the spin feature, blocking when attempting to lock a mutex which is already locked on the main thread will panic and thereby crash the application.
To resolve the issue, use a spinlock on the browser main thread, through the
wasm_safe_mutexcrate. Web worker threads will continue to sleep when locking a mutex as usual.Note: this isn't the most beautiful solution, as there are now 3 mutex implementations in the crate - unfortunately the ecosystem is in discord, with the standard library Mutex happily blocking the main thread on Wasm when this is a known problem, and browsers refusing to allow blocking on the main thread.
Theoretically we could only use
wasm_safe_mutexfor everything, as this provides the ability to spin or block and has async support, however (without any inspection whatsoever) I imagine that long-term the standard library's mutex is likely to be more efficient, especially as it would continuously receive updates and improvements over time from the entire community.As such I have guarded this change behind flags so that
wasm_safe_mutexis only used on Wasm platforms.Fixes #173.