Implementation Of Mutex And pthread In Emscripten

[awt]

Hi,

I was just going thru the source when I noticed the presence of mutex in emscripten/system/include/libcxx/mutex and pthreads in emscripten/system/include/libc/pthread.h. Since the browser is single-threaded, may I know how do we implement mutexes and pthreads under the hoods? Do we really implement synchronization in a multi-threading context? Is this supported only in FireFox Nightly or in Chrome as well? Thanks.

[Floh]

These used to be empty placeholder functions so that code would at least compile and link.

However, there *is* work going on to enable pthreads-style shared-memory-multithreading in emscripten and Firefox, see here: 

https://blog.mozilla.org/javascript/2015/02/26/the-path-to-parallel-javascript/

and here:

https://groups.google.com/forum/#!topic/emscripten-discuss/gQQRjajQ6iY

Unfortunately I didn't get around to try this out yet.

Cheers,

-Floh

[Robert Goulet]

pthread implementation on its own in Emscripten seems to be working fine so far. The only problem we have for the moment is we can't use it with WebGL (Firefox Nightly). It produces an assert about the SharedArrayBuffer type not being a correct type argument for some GL calls.

[awt]

Thanks for the reply. Do you know if threads are emulated using webworkers or setTimeout in Emscripten?

[Robert Goulet]

They are using Web Workers, and that means you also need the SharedArrayBuffers from Firefox Nightly to make this work. This is not supported (yet) in Google Chrome AFAIK.

[awt]

ok thanks.