Re: [w3c/ServiceWorker] Define scope to job queue map struct (#1183)

jungkees commented on this pull request.



> @@ -2435,7 +2437,9 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
     * For *register* and *update* <a>jobs</a>, both their [=job/scope url=] and the [=job/script url=] are the same.
     * For *unregister* <a>jobs</a>, their [=job/scope url=] is the same.
 
-  A <dfn id="dfn-job-queue">job queue</dfn> is a thread safe queue used to synchronize the set of concurrent <a>jobs</a>. The <a>job queue</a> contains <a>jobs</a> as its elements. The <a>job queue</a> *should* satisfy the general properties of FIFO queue. A user agent *must* maintain a separate <a>job queue</a> for each [=/service worker registration=] keyed by its [=service worker registration/scope url=]. A <a>job queue</a> is initially empty. Unless stated otherwise, the <a>job queue</a> referenced from the algorithm steps is a <a>job queue</a> for the <a>job</a>'s [=job/scope url=].
+  A <dfn id="dfn-job-queue">job queue</dfn> is a thread safe [=queue=] used to synchronize the set of concurrent [=jobs=]. The [=job queue=] contains [=jobs=] as its [=queue/items=]. A [=job queue=] is initially empty.

The situation isn't clear. Spec needs thread-safeness as multiple clients share job queues. Chromium is scheduling jobs in the browser process's io thread, which means the scheduling requests are already serialized in a single thread there. I'm not sure about Gecko. https://dxr.mozilla.org/mozilla-central/source/dom/workers/ServiceWorkerManager.cpp#936 called in ServiceWorkerManager::Register is on the main thread. @wanderview, is this main thread of the browser process's main thread or each web content process's main thread? I couldn't find any IPC bridge along the call path, so presume the multi-process migration hasn't come to SW part yet? Could you explain?

Anyway, spec needs a thread concept where we can queue such jobs to serialize. There have been discussions, but it hasn't spec'ed yet. For now, i'd like to defer to those spec efforts and just leave it as "thread safe" without any additional wording. I think it'd be difficult to be clear about the order of the jobs in prose.

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