Intent to Extend Experiment: Shared Array Buffers, Atomics and Futex APIs

Contact emails

va...@chromium.org, cl...@chromium.org

Explainer

None

Specification

https://tc39.github.io/ecma262/#sec-sharedarraybuffer-objects

Design docs

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer

Summary

Adds the JavaScript type SharedArrayBuffer gated behind COOP/COEP. The concept of a SharedArrayBuffer is that a message to a worker, is posted but instead of copying the content of the array just a reference to it is shared. The Atomic API provides atomic loads and stores and Read/Modify/Write accesses to SharedArrayBuffers. The Atomic.wait provides the ability for a worker to wait for another worker to signal it, without having to spinlock.

Blink component

Blink>JavaScript

Search tags

SharedArrayBuffer, SAB

TAG review

https://github.com/w3ctag/design-reviews/issues/471

TAG review status

Pending

Origin Trial Name

SharedArrayBuffers in non-isolated pages on Desktop platforms

Chromium Trial Name

UnrestrictedSharedArrayBuffer

Link to origin trial feedback summary

https://bugs.chromium.org/p/chromium/issues/entry?components=Internals%3ESandbox%3ESiteIsolation

Origin Trial documentation link

https://developer.chrome.com/blog/enabling-shared-array-buffer/

Risks

Goals for experimentation

Reason this experiment is being extended

This is a deprecation trial, and we're giving more time to websites to stop using the deprecated behavior.

Reason this experiment is being extended

The release of DocumentIsolationPolicy in M137 is helping developers adopt crossOriginIsolation as a way out of this reverse Origin Trial. However, it will still take time for developers to adopt. We would like to extend the OT as the final extension and give developers 6 milestones to get out of this reverse Origin Trial. Once this is approved and developers have requested their token, we will close this trial so that no further origins adopt the deprecated behavior.

Ongoing technical constraints

Debuggability

DevTools warning in case SAB is used in none COI context is in place

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

No

Is this feature fully tested by web-platform-tests?

Yes

https://source.chromium.org/chromium/chromium/src/+/master:third_party/blink/web_tests/external/wpt/html/infrastructure/safe-passing-of-structured-data/shared-array-buffers/no-coop-coep.https.any.js https://github.com/tc39/test262/tree/master/test/built-ins/SharedArrayBuffer https://github.com/tc39/test262/tree/master/test/built-ins/Atomics

Flag name on about://flags

Finch feature name

None

Non-finch justification

None

Requires code in //chrome?

False

Tracking bug

https://bugs.chromium.org/p/chromium/issues/detail?id=709179

Launch bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1138860

Estimated milestones

Origin trial desktop first	92
Origin trial desktop last	131
Origin trial extension 1 end milestone	109
Origin trial extension 2 end milestone	131
Origin trial extension 3 end milestone	124
Origin trial extension 4 end milestone	136
Origin trial extension 5 end milestone	142
DevTrial on desktop	60
DevTrial on Android	88

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/4570991992766464?gate=6222972867837952

Links to previous Intent discussions

Intent to Experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/1NKvbIj3dq4
Intent to Extend Experiment 1: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAH0ixBN2JhcYtpT4UYKcAfHt1e0Wz_Uxz0CkXcAntguhbmyNCA%40mail.gmail.com
Intent to Extend Experiment 2: https://groups.google.com/u/1/a/chromium.org/g/blink-dev/c/4tDmckQLZLQ
Intent to Extend Experiment 3: https://groups.google.com/a/chromium.org/g/blink-dev/c/UospzV3lZMk/m/X9K0k8kuAQAJ
Intent to Extend Experiment 4: https://groups.google.com/a/chromium.org/g/blink-dev/c/A4CR6MIVzds/m/rpsWnzq6AAAJ?e=48417069
Intent to Ship: https://groups.google.com/a/chromium.org/g/blink-dev/c/1NKvbIj3dq4