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// |reftest| skip
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//-----------------------------------------------------------------------
var summary = "Lamport Bakery's algorithm for mutual exclusion";
// Adapted from pseudocode in Wikipedia:
// http://en.wikipedia.org/wiki/Lamport%27s_bakery_algorithm
printStatus(summary);
var N = 15; // Number of threads.
var LOOP_COUNT = 10; // Number of times each thread should loop
function range(n) {
for (let i = 0; i < n; i++)
yield i;
}
function max(a) {
let x = Number.NEGATIVE_INFINITY;
for each (let i in a)
if (i > x)
x = i;
return x;
}
// the mutex mechanism
var entering = [false for (i in range(N))];
var ticket = [0 for (i in range(N))];
// the object being protected
var counter = 0;
function lock(i)
{
entering[i] = true;
ticket[i] = 1 + max(ticket);
entering[i] = false;
for (let j = 0; j < N; j++) {
// If thread j is in the middle of getting a ticket, wait for that to
// finish.
while (entering[j])
;
// Wait until all threads with smaller ticket numbers or with the same
// ticket number, but with higher priority, finish their work.
while ((ticket[j] != 0) && ((ticket[j] < ticket[i]) ||
((ticket[j] == ticket[i]) && (i < j))))
;
}
}
function unlock(i) {
ticket[i] = 0;
}
function worker(i) {
for (let k = 0; k < LOOP_COUNT; k++) {
lock(i);
// The critical section
let x = counter;
sleep(0.003);
counter = x + 1;
unlock(i);
}
return 'ok';
}
function makeWorker(id) {
return function () { return worker(id); };
}
var expect;
var actual;
if (typeof scatter == 'undefined' || typeof sleep == 'undefined') {
print('Test skipped. scatter or sleep not defined.');
expect = actual = 'Test skipped.';
} else {
scatter([makeWorker(i) for (i in range(N))]);
expect = "counter: " + (N * LOOP_COUNT);
actual = "counter: " + counter;
}
reportCompare(expect, actual, summary);
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