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Atomics.notify

The static Atomics.notify() method notifies up some agents that are sleeping in the wait queue.

Note: This operation works with a shared Int32Array only.
It will return 0 on non-shared ArrayBuffer objects.

Syntax

Atomics.notify(typedArray, index, count)

Parameters

typedArray
A shared Int32Array.
index
The position in the typedArray to wake up on.
count Optional
The number of sleeping agents to notify. Defaults to +Infinity.

Return value

  • Returns the number of woken up agents.
  • Returns 0, if a non-shared ArrayBuffer object is used.

Exceptions

Examples

Using notify

Given a shared Int32Array:

const sab = new SharedArrayBuffer(1024);
const int32 = new Int32Array(sab);

A reading thread is sleeping and waiting on location 0 which is expected to be 0. As long as that is true, it will not go on. However, once the writing thread has stored a new value, it will be notified by the writing thread and return the new value (123).

Atomics.wait(int32, 0, 0);
console.log(int32[0]); // 123

A writing thread stores a new value and notifies the waiting thread once it has written:

console.log(int32[0]); // 0;
Atomics.store(int32, 0, 123); 
Atomics.notify(int32, 0, 1);

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
notify 68
68
60 — 63
Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.
Uses the non-standard name: wake
79 78
78
63
Disabled
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
Disabled From version 63: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
57
Disabled
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
Uses the non-standard name: wake
Disabled From version 57: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
55 — 57
48 — 55
Disabled
Disabled From version 48 until version 55 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
46 — 48
Disabled
The count parameter defaults to 0 instead of the later-specified +Infinity.
Uses the non-standard name: futexWake
Disabled From version 46 until version 48 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
No No 10.1 — 11.1
10.1 — 11.1
Uses the non-standard name: wake
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
notify 60 — 63
60 — 63
Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.
Uses the non-standard name: wake
60 — 63
60 — 63
Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.
Uses the non-standard name: wake
63
Disabled
63
Disabled
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
Disabled From version 63: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
57
Disabled
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
Uses the non-standard name: wake
Disabled From version 57: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
55 — 57
48 — 55
Disabled
Disabled From version 48 until version 55 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
46 — 48
Disabled
The count parameter defaults to 0 instead of the later-specified +Infinity.
Uses the non-standard name: futexWake
Disabled From version 46 until version 48 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.
No 10.3 — 11.3 No
No
Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.
Uses the non-standard name: wake
Server
Node.js
notify 8.10.0
8.10.0
Uses the non-standard name: wake

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics/notify