[webkit-dev] Merging the iOS port to svn.webkit.org (Re: WebCore and interlocking threads)

Maciej Stachowiak mjs at apple.com
Fri Feb 8 17:13:54 PST 2013

On Feb 8, 2013, at 4:48 PM, Adam Barth <abarth at webkit.org> wrote:

> One simple example is V8, which stores the current v8::Isolate in
> thread-local storage.
> However, the problem is certainly not limited to V8, nor is it even
> limited to the code we're using today.  Running WebCore on multiple
> interlocked threads imposes restrictions on how all the code called by
> WebCore use TLS.  Those restrictions might be worthwhile or they might
> not be worthwhile.

I think "running WebCore on multiple interlocked threads" is not a good description of how the iOS threading model works. See my other message. I'd be glad to explain it in more detail, if you would like to understand how it works.

> Before adding these restrictions to WebCore, we should discuss them as
> a community and come to consensus about whether their benefits
> outweigh their costs.  I don't think it's appropriate for Apple to
> impose these restrictions on WebCore unilaterally.

There's not really significant "restrictions to WebCore" - the code exists and is shipping for years, and we've never experienced issues with TLS  in the way you are concerned about. Probably because the use of WebCore from the main thread is quite limited.

If you want to see for yourself, uou can see the fallout in the iOS WebCore tarball dumps that Apple offers. Or we can walk you through it in person. It's probably not practical to explain in full detail by email.


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