[browser][mt] Upgrade emscripten

[lambdageek]

In a threaded .NET runtime, Emscripten prints this to the JS console even if C# user code doesn't do any threading

Blocking on the main thread is very dangerous, see https://emscripten.org/docs/porting/pthreads.html#blocking-on-the-main-browser-thread

This comes from https://github.com/emscripten-core/emscripten/blob/678d7d8881a810d14f52bb3b7e72a8c337b571ba/src/library_pthread.js#L785

which gets called from various pthread primitives that the runtime calls, such as pthread_join or pthread_cond_timedwait.

We should try setting -s ALLOW_BLOCKING_ON_MAIN_THREAD=false and investigate whether the blocking operations are really necessary. If fixing the blocking is infeasible, we should consider overriding Module.PThread.emscripten_check_blocking_allowed to not nag.

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Issue Details

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In a threaded .NET runtime, Emscripten prints this to the JS console even if C# user code doesn't do any threading

Blocking on the main thread is very dangerous, see https://emscripten.org/docs/porting/pthreads.html#blocking-on-the-main-browser-thread

This comes from https://github.com/emscripten-core/emscripten/blob/678d7d8881a810d14f52bb3b7e72a8c337b571ba/src/library_pthread.js#L785

which gets called from various pthread primitives that the runtime calls, such as pthread_join or pthread_cond_timedwait.

We should try setting -s ALLOW_BLOCKING_ON_MAIN_THREAD=false and investigate whether the blocking operations are really necessary. If fixing the blocking is infeasible, we should consider overriding Module.PThread.emscripten_check_blocking_allowed to not nag.

Author:	lambdageek
Assignees:	-
Labels:	arch-wasm, area-Threading-mono
Milestone:	8.0.0

[pavelsavara]

This is how mono thread pool joins threads in order to finalize them.

Other significant use is mono_os_mutex_lock which is used in about 40 places

• GC
• threadpool
• debugger
• mini

I think that we are unlikely to be able to remove it.
Alternate strategy could be to run mono always on the worker.

[pavelsavara]

I think the message could be supressed in newer versions of emscripten.

Should we bump version of emscripten ?
Should we also switch to using https://github.com/dotnet/emscripten/ in our inner loop ?

@radekdoulik @lewing