Atomics.wake()

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

Syntax

Atomics.wake(typedArray, index, count)

Parameters

typedArray

A shared Int32Array.

index

The position in the typedArray to wake up on.

count

The number of sleeping agents to wake. Defaults to +Infinity.

Return value

A number of woken up agents.

Exceptions

• Throws a TypeError, if typedArray is not a shared Int32Array.
• Throws a RangeError, if index is out of bounds in the typedArray.

Examples

Given a shared Int32Array:

var sab = new SharedArrayBuffer(1024);
var 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 woken up 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 wakes up the waiting thread once it has written:

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

Specifications

Browser compatibility

[1] In Firefox version 46 until version 54, this feature is disabled by a preference setting. In about:config, set javascript.options.shared_memory to true. 

[2] The implementation is under development and needs these runtime flags: --js-flags=--harmony-sharedarraybuffer --enable-blink-feature=SharedArrayBuffer

[3] In versions 46 and 47, this method was named Atomics.futexWake() and the count parameter defaulted to 0.

[4] The count parameter defaults to 0, instead of +Infinity.

See also

• Atomics
• Atomics.wait()