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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 compatibility

Desktop Mobile Server
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet Deno Node.js
notify
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.
79
78
63
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
57
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
55-57
48-55
46-48
The count parameter defaults to 0 instead of the later-specified +Infinity.
No
No
15.2
Like SharedArrayBuffer, Atomics is gated behind COOP/COEP. For more detail, read Making your website "cross-origin isolated" using COOP and COEP.
10.1-11.1
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.
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.
63
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
57
Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).
55-57
48-55
46-48
The count parameter defaults to 0 instead of the later-specified +Infinity.
No
15.2
Like SharedArrayBuffer, Atomics is gated behind COOP/COEP. For more detail, read Making your website "cross-origin isolated" using COOP and COEP.
10.3-11.3
No
1.0
8.10.0

See also

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