// Copyright (C) 2017 Mozilla Corporation. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
description: >
Collection of functions used to interact with Atomics.* operations across agent boundaries.
---*/
/**
* @return {String} A report sent from an agent.
*/
{
// This is only necessary because the original
// $262.agent.getReport API was insufficient.
//
// All runtimes currently have their own
// $262.agent.getReport which is wrong, so we
// will pave over it with a corrected version.
//
// Binding $262.agent is necessary to prevent
// breaking SpiderMonkey's $262.agent.getReport
let getReport = $262.agent.getReport.bind($262.agent);
$262.agent.getReport = function() {
var r;
while ((r = getReport()) == null) {
$262.agent.sleep(1);
}
return r;
};
}
/**
*
* Share a given Int32Array or BigInt64Array to all running agents. Ensure that the
* provided TypedArray is a "shared typed array".
*
* NOTE: Migrating all tests to this API is necessary to prevent tests from hanging
* indefinitely when a SAB is sent to a worker but the code in the worker attempts to
* create a non-sharable TypedArray (something that is not Int32Array or BigInt64Array).
* When that scenario occurs, an exception is thrown and the agent worker can no
* longer communicate with any other threads that control the SAB. If the main
* thread happens to be spinning in the $262.agent.waitUntil() while loop, it will never
* meet its termination condition and the test will hang indefinitely.
*
* Because we've defined $262.agent.broadcast(SAB) in
* https://github.com/tc39/test262/blob/master/INTERPRETING.md, there are host implementations
* that assume compatibility, which must be maintained.
*
*
* $262.agent.safeBroadcast(TA) should not be included in
* https://github.com/tc39/test262/blob/master/INTERPRETING.md
*
*
* @param {(Int32Array|BigInt64Array)} typedArray An Int32Array or BigInt64Array with a SharedArrayBuffer
*/
$262.agent.safeBroadcast = function(typedArray) {
let Constructor = Object.getPrototypeOf(typedArray).constructor;
let temp = new Constructor(
new SharedArrayBuffer(Constructor.BYTES_PER_ELEMENT)
);
try {
// This will never actually wait, but that's fine because we only
// want to ensure that this typedArray CAN be waited on and is shareable.
Atomics.wait(temp, 0, Constructor === Int32Array ? 1 : BigInt(1));
} catch (error) {
$ERROR(`${Constructor.name} cannot be used as a shared typed array. (${error})`);
}
$262.agent.broadcast(typedArray.buffer);
};
/**
* With a given Int32Array or BigInt64Array, wait until the expected number of agents have
* reported themselves by calling:
*
* Atomics.add(typedArray, index, 1);
*
* @param {(Int32Array|BigInt64Array)} typedArray An Int32Array or BigInt64Array with a SharedArrayBuffer
* @param {number} index The index of which all agents will report.
* @param {number} expected The number of agents that are expected to report as active.
*/
$262.agent.waitUntil = function(typedArray, index, expected) {
var agents = 0;
while ((agents = Atomics.load(typedArray, index)) !== expected) {
/* nothing */
}
assert.sameValue(agents, expected, "Reporting number of 'agents' equals the value of 'expected'");
};
/**
* Timeout values used throughout the Atomics tests. All timeouts are specified in milliseconds.
*
* @property {number} yield Used for `$262.agent.tryYield`. Must not be used in other functions.
* @property {number} small Used when agents will always timeout and `Atomics.wake` is not part
* of the test semantics. Must be larger than `$262.agent.timeouts.yield`.
* @property {number} long Used when some agents may timeout and `Atomics.wake` is called on some
* agents. The agents are required to wait and this needs to be observable
* by the main thread.
* @property {number} huge Used when `Atomics.wake` is called on all waiting agents. The waiting
* must not timeout. The agents are required to wait and this needs to be
* observable by the main thread. All waiting agents must be woken by the
* main thread.
*
* Usage for `$262.agent.timeouts.small`:
* const WAIT_INDEX = 0;
* const RUNNING = 1;
* const TIMEOUT = $262.agent.timeouts.small;
* const i32a = new Int32Array(new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 2));
*
* $262.agent.start(`
* $262.agent.receiveBroadcast(function(sab) {
* const i32a = new Int32Array(sab);
* Atomics.add(i32a, ${RUNNING}, 1);
*
* $262.agent.report(Atomics.wait(i32a, ${WAIT_INDEX}, 0, ${TIMEOUT}));
*
* $262.agent.leaving();
* });
* `);
* $262.agent.safeBroadcast(i32a.buffer);
*
* // Wait until the agent was started and then try to yield control to increase
* // the likelihood the agent has called `Atomics.wait` and is now waiting.
* $262.agent.waitUntil(i32a, RUNNING, 1);
* $262.agent.tryYield();
*
* // The agent is expected to time out.
* assert.sameValue($262.agent.getReport(), "timed-out");
*
*
* Usage for `$262.agent.timeouts.long`:
* const WAIT_INDEX = 0;
* const RUNNING = 1;
* const NUMAGENT = 2;
* const TIMEOUT = $262.agent.timeouts.long;
* const i32a = new Int32Array(new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 2));
*
* for (let i = 0; i < NUMAGENT; i++) {
* $262.agent.start(`
* $262.agent.receiveBroadcast(function(sab) {
* const i32a = new Int32Array(sab);
* Atomics.add(i32a, ${RUNNING}, 1);
*
* $262.agent.report(Atomics.wait(i32a, ${WAIT_INDEX}, 0, ${TIMEOUT}));
*
* $262.agent.leaving();
* });
* `);
* }
* $262.agent.safeBroadcast(i32a.buffer);
*
* // Wait until the agents were started and then try to yield control to increase
* // the likelihood the agents have called `Atomics.wait` and are now waiting.
* $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);
* $262.agent.tryYield();
*
* // Wake exactly one agent.
* assert.sameValue(Atomics.wake(i32a, WAIT_INDEX, 1), 1);
*
* // When it doesn't matter how many agents were woken at once, a while loop
* // can be used to make the test more resilient against intermittent failures
* // in case even though `tryYield` was called, the agents haven't started to
* // wait.
* //
* // // Repeat until exactly one agent was woken.
* // var woken = 0;
* // while ((woken = Atomics.wake(i32a, WAIT_INDEX, 1)) !== 0) ;
* // assert.sameValue(woken, 1);
*
* // One agent was woken and the other one timed out.
* const reports = [$262.agent.getReport(), $262.agent.getReport()];
* assert(reports.includes("ok"));
* assert(reports.includes("timed-out"));
*
*
* Usage for `$262.agent.timeouts.huge`:
* const WAIT_INDEX = 0;
* const RUNNING = 1;
* const NUMAGENT = 2;
* const TIMEOUT = $262.agent.timeouts.huge;
* const i32a = new Int32Array(new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 2));
*
* for (let i = 0; i < NUMAGENT; i++) {
* $262.agent.start(`
* $262.agent.receiveBroadcast(function(sab) {
* const i32a = new Int32Array(sab);
* Atomics.add(i32a, ${RUNNING}, 1);
*
* $262.agent.report(Atomics.wait(i32a, ${WAIT_INDEX}, 0, ${TIMEOUT}));
*
* $262.agent.leaving();
* });
* `);
* }
* $262.agent.safeBroadcast(i32a.buffer);
*
* // Wait until the agents were started and then try to yield control to increase
* // the likelihood the agents have called `Atomics.wait` and are now waiting.
* $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);
* $262.agent.tryYield();
*
* // Wake all agents.
* assert.sameValue(Atomics.wake(i32a, WAIT_INDEX), NUMAGENT);
*
* // When it doesn't matter how many agents were woken at once, a while loop
* // can be used to make the test more resilient against intermittent failures
* // in case even though `tryYield` was called, the agents haven't started to
* // wait.
* //
* // // Repeat until all agents were woken.
* // for (var wokenCount = 0; wokenCount < NUMAGENT; ) {
* // var woken = 0;
* // while ((woken = Atomics.wake(i32a, WAIT_INDEX)) !== 0) ;
* // // Maybe perform an action on the woken agents here.
* // wokenCount += woken;
* // }
*
* // All agents were woken and none timeout.
* for (var i = 0; i < NUMAGENT; i++) {
* assert($262.agent.getReport(), "ok");
* }
*/
$262.agent.timeouts = {
yield: 100,
small: 200,
long: 1000,
huge: 10000,
};
/**
* Try to yield control to the agent threads.
*
* Usage:
* const VALUE = 0;
* const RUNNING = 1;
* const i32a = new Int32Array(new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 2));
*
* $262.agent.start(`
* $262.agent.receiveBroadcast(function(sab) {
* const i32a = new Int32Array(sab);
* Atomics.add(i32a, ${RUNNING}, 1);
*
* Atomics.store(i32a, ${VALUE}, 1);
*
* $262.agent.leaving();
* });
* `);
* $262.agent.safeBroadcast(i32a.buffer);
*
* // Wait until agent was started and then try to yield control.
* $262.agent.waitUntil(i32a, RUNNING, 1);
* $262.agent.tryYield();
*
* // Note: This result is not guaranteed, but should hold in practice most of the time.
* assert.sameValue(Atomics.load(i32a, VALUE), 1);
*
* The default implementation simply waits for `$262.agent.timeouts.yield` milliseconds.
*/
$262.agent.tryYield = function() {
$262.agent.sleep($262.agent.timeouts.yield);
};
/**
* Try to sleep the current agent for the given amount of milliseconds. It is acceptable,
* but not encouraged, to ignore this sleep request and directly continue execution.
*
* The default implementation calls `$262.agent.sleep(ms)`.
*
* @param {number} ms Time to sleep in milliseconds.
*/
$262.agent.trySleep = function(ms) {
$262.agent.sleep(ms);
};