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+/* 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/. */
+
+/**
+ * Managing safe shutdown of asynchronous services.
+ *
+ * Firefox shutdown is composed of phases that take place
+ * sequentially. Typically, each shutdown phase removes some
+ * capabilities from the application. For instance, at the end of
+ * phase profileBeforeChange, no service is permitted to write to the
+ * profile directory (with the exception of Telemetry). Consequently,
+ * if any service has requested I/O to the profile directory before or
+ * during phase profileBeforeChange, the system must be informed that
+ * these requests need to be completed before the end of phase
+ * profileBeforeChange. Failing to inform the system of this
+ * requirement can (and has been known to) cause data loss.
+ *
+ * Example: At some point during shutdown, the Add-On Manager needs to
+ * ensure that all add-ons have safely written their data to disk,
+ * before writing its own data. Since the data is saved to the
+ * profile, this must be completed during phase profileBeforeChange.
+ *
+ * AsyncShutdown.profileBeforeChange.addBlocker(
+ * "Add-on manager: shutting down",
+ * function condition() {
+ * // Do things.
+ * // Perform I/O that must take place during phase profile-before-change
+ * return promise;
+ * }
+ * });
+ *
+ * In this example, function |condition| will be called at some point
+ * during phase profileBeforeChange and phase profileBeforeChange
+ * itself is guaranteed to not terminate until |promise| is either
+ * resolved or rejected.
+ */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyServiceGetter(
+ lazy,
+ "gDebug",
+ "@mozilla.org/xpcom/debug;1",
+ "nsIDebug2"
+);
+
+// `true` if this is a content process, `false` otherwise.
+// It would be nicer to go through `Services.appinfo`, but some tests need to be
+// able to replace that field with a custom implementation before it is first
+// called.
+const isContent =
+ // eslint-disable-next-line mozilla/use-services
+ Cc["@mozilla.org/xre/app-info;1"].getService(Ci.nsIXULRuntime).processType ==
+ Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT;
+
+// Display timeout warnings after 10 seconds
+const DELAY_WARNING_MS = 10 * 1000;
+
+// Crash the process if shutdown is really too long
+// (allowing for sleep).
+const PREF_DELAY_CRASH_MS = "toolkit.asyncshutdown.crash_timeout";
+var DELAY_CRASH_MS = Services.prefs.getIntPref(PREF_DELAY_CRASH_MS, 60 * 1000); // One minute
+Services.prefs.addObserver(PREF_DELAY_CRASH_MS, function () {
+ DELAY_CRASH_MS = Services.prefs.getIntPref(PREF_DELAY_CRASH_MS);
+});
+
+/**
+ * Any addBlocker calls that failed. We add this into barrier wait
+ * crash annotations to help with debugging. When we fail to add
+ * shutdown blockers that can break shutdown. We track these globally
+ * rather than per barrier because one failure mode is when the
+ * barrier has already finished by the time addBlocker is invoked -
+ * but the failure to add the blocker may result in later barriers
+ * waiting indefinitely, so the debug information is still useful
+ * for those later barriers. See bug 1801674 for more context.
+ */
+let gBrokenAddBlockers = [];
+
+/**
+ * A set of Promise that supports waiting.
+ *
+ * Promise items may be added or removed during the wait. The wait will
+ * resolve once all Promise items have been resolved or removed.
+ */
+function PromiseSet() {
+ /**
+ * key: the Promise passed pass the client of the `PromiseSet`.
+ * value: an indirection on top of `key`, as an object with
+ * the following fields:
+ * - indirection: a Promise resolved if `key` is resolved or
+ * if `resolve` is called
+ * - resolve: a function used to resolve the indirection.
+ */
+ this._indirections = new Map();
+ // Once all the tracked promises have been resolved we are done. Once Wait()
+ // resolves, it should not be possible anymore to add further promises.
+ // This covers for a possibly rare case, where something may try to add a
+ // blocker after wait() is done, that would never be awaited for.
+ this._done = false;
+}
+PromiseSet.prototype = {
+ /**
+ * Wait until all Promise have been resolved or removed.
+ *
+ * Note that calling `wait()` causes Promise to be removed from the
+ * Set once they are resolved.
+ * @param {function} onDoneCb invoked synchronously once all the entries
+ * have been handled and no new entries will be accepted.
+ * @return {Promise} Resolved once all Promise have been resolved or removed,
+ * or rejected after at least one Promise has rejected.
+ */
+ wait(onDoneCb) {
+ // Pick an arbitrary element in the map, if any exists.
+ let entry = this._indirections.entries().next();
+ if (entry.done) {
+ // No indirections left, we are done.
+ this._done = true;
+ onDoneCb();
+ return Promise.resolve();
+ }
+
+ let [, indirection] = entry.value;
+ let promise = indirection.promise;
+ promise = promise.then(() =>
+ // At this stage, the entry has been cleaned up.
+ this.wait(onDoneCb)
+ );
+ return promise;
+ },
+
+ /**
+ * Add a new Promise to the set.
+ *
+ * Calls to wait (including ongoing calls) will only return once
+ * `key` has either resolved or been removed.
+ */
+ add(key) {
+ if (this._done) {
+ throw new Error("Wait is complete, cannot add further promises.");
+ }
+ this._ensurePromise(key);
+ let indirection = Promise.withResolvers();
+ key
+ .then(
+ x => {
+ // Clean up immediately.
+ // This needs to be done before the call to `resolve`, otherwise
+ // `wait()` may loop forever.
+ this._indirections.delete(key);
+ indirection.resolve(x);
+ },
+ err => {
+ this._indirections.delete(key);
+ indirection.reject(err);
+ }
+ )
+ .finally(() => {
+ this._indirections.delete(key);
+ // Normally the promise is resolved or rejected, but if its global
+ // goes away, only finally may be invoked. In all the other cases this
+ // is a no-op since the promise has been fulfilled already.
+ indirection.reject(
+ new Error("Promise not fulfilled, did it lost its global?")
+ );
+ });
+ this._indirections.set(key, indirection);
+ },
+
+ /**
+ * Remove a Promise from the set.
+ *
+ * Calls to wait (including ongoing calls) will ignore this promise,
+ * unless it is added again.
+ */
+ delete(key) {
+ this._ensurePromise(key);
+ let value = this._indirections.get(key);
+ if (!value) {
+ return false;
+ }
+ this._indirections.delete(key);
+ value.resolve();
+ return true;
+ },
+
+ _ensurePromise(key) {
+ if (!key || typeof key != "object") {
+ throw new Error("Expected an object");
+ }
+ if (!("then" in key) || typeof key.then != "function") {
+ throw new Error("Expected a Promise");
+ }
+ },
+};
+
+/**
+ * Display a warning.
+ *
+ * As this code is generally used during shutdown, there are chances
+ * that the UX will not be available to display warnings on the
+ * console. We therefore use dump() rather than Cu.reportError().
+ */
+function log(msg, prefix = "", error = null) {
+ try {
+ dump(prefix + msg + "\n");
+ if (error) {
+ dump(prefix + error + "\n");
+ if (typeof error == "object" && "stack" in error) {
+ dump(prefix + error.stack + "\n");
+ }
+ }
+ } catch (ex) {
+ dump("INTERNAL ERROR in AsyncShutdown: cannot log message.\n");
+ }
+}
+const PREF_DEBUG_LOG = "toolkit.asyncshutdown.log";
+var DEBUG_LOG = Services.prefs.getBoolPref(PREF_DEBUG_LOG, false);
+Services.prefs.addObserver(PREF_DEBUG_LOG, function () {
+ DEBUG_LOG = Services.prefs.getBoolPref(PREF_DEBUG_LOG);
+});
+
+function debug(msg, error = null) {
+ if (DEBUG_LOG) {
+ log(msg, "DEBUG: ", error);
+ }
+}
+function warn(msg, error = null) {
+ log(msg, "WARNING: ", error);
+}
+function fatalerr(msg, error = null) {
+ log(msg, "FATAL ERROR: ", error);
+}
+
+// Utility function designed to get the current state of execution
+// of a blocker.
+// We are a little paranoid here to ensure that in case of evaluation
+// error we do not block the AsyncShutdown.
+function safeGetState(fetchState) {
+ if (!fetchState) {
+ return "(none)";
+ }
+ let data, string;
+ try {
+ // Evaluate fetchState(), normalize the result into something that we can
+ // safely stringify or upload.
+ let state = fetchState();
+ if (!state) {
+ return "(none)";
+ }
+ string = JSON.stringify(state);
+ data = JSON.parse(string);
+ // Simplify the rest of the code by ensuring that we can simply
+ // concatenate the result to a message.
+ if (data && typeof data == "object") {
+ data.toString = function () {
+ return string;
+ };
+ }
+ return data;
+ } catch (ex) {
+ // Make sure that this causes test failures
+ Promise.reject(ex);
+
+ if (string) {
+ return string;
+ }
+ try {
+ return "Error getting state: " + ex + " at " + ex.stack;
+ } catch (ex2) {
+ return "Error getting state but could not display error";
+ }
+ }
+}
+
+/**
+ * Countdown for a given duration, skipping beats if the computer is too busy,
+ * sleeping or otherwise unavailable.
+ *
+ * @param {number} delay An approximate delay to wait in milliseconds (rounded
+ * up to the closest second).
+ *
+ * @return Deferred
+ */
+function looseTimer(delay) {
+ let DELAY_BEAT = 1000;
+ let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+ let beats = Math.ceil(delay / DELAY_BEAT);
+ let deferred = Promise.withResolvers();
+ timer.initWithCallback(
+ function () {
+ if (beats <= 0) {
+ deferred.resolve();
+ }
+ --beats;
+ },
+ DELAY_BEAT,
+ Ci.nsITimer.TYPE_REPEATING_PRECISE_CAN_SKIP
+ );
+ // Ensure that the timer is both canceled once we are done with it
+ // and not garbage-collected until then.
+ deferred.promise.then(
+ () => timer.cancel(),
+ () => timer.cancel()
+ );
+ return deferred;
+}
+
+/**
+ * Given an nsIStackFrame object, find the caller filename, line number,
+ * and stack if necessary, and return them as an object.
+ *
+ * @param {nsIStackFrame} topFrame Top frame of the call stack.
+ * @param {string} filename Pre-supplied filename or null if unknown.
+ * @param {number} lineNumber Pre-supplied line number or null if unknown.
+ * @param {string} stack Pre-supplied stack or null if unknown.
+ *
+ * @return object
+ */
+function getOrigin(topFrame, filename = null, lineNumber = null, stack = null) {
+ try {
+ // Determine the filename and line number of the caller.
+ let frame = topFrame;
+
+ for (; frame && frame.filename == topFrame.filename; frame = frame.caller) {
+ // Climb up the stack
+ }
+
+ if (filename == null) {
+ filename = frame ? frame.filename : "?";
+ }
+ if (lineNumber == null) {
+ lineNumber = frame ? frame.lineNumber : 0;
+ }
+ if (stack == null) {
+ // Now build the rest of the stack as a string, using Task.jsm's rewriting
+ // to ensure that we do not lose information at each call to `Task.spawn`.
+ stack = [];
+ while (frame != null) {
+ stack.push(frame.filename + ":" + frame.name + ":" + frame.lineNumber);
+ frame = frame.caller;
+ }
+ }
+
+ return {
+ filename,
+ lineNumber,
+ stack,
+ };
+ } catch (ex) {
+ return {
+ filename: "<internal error: could not get origin>",
+ lineNumber: -1,
+ stack: "<internal error: could not get origin>",
+ };
+ }
+}
+
+/**
+ * {string} topic -> phase
+ */
+var gPhases = new Map();
+
+export var AsyncShutdown = {
+ /**
+ * Access function getPhase. For testing purposes only.
+ */
+ get _getPhase() {
+ let accepted = Services.prefs.getBoolPref(
+ "toolkit.asyncshutdown.testing",
+ false
+ );
+ if (accepted) {
+ return getPhase;
+ }
+ return undefined;
+ },
+
+ /**
+ * This constant is used as the amount of milliseconds to allow shutdown to be
+ * blocked until we crash the process forcibly and is read from the
+ * 'toolkit.asyncshutdown.crash_timeout' pref.
+ */
+ get DELAY_CRASH_MS() {
+ return DELAY_CRASH_MS;
+ },
+};
+
+/**
+ * Register a new phase.
+ *
+ * @param {string} topic The notification topic for this Phase.
+ * @see {https://developer.mozilla.org/en-US/docs/Observer_Notifications}
+ */
+function getPhase(topic) {
+ let phase = gPhases.get(topic);
+ if (phase) {
+ return phase;
+ }
+ let spinner = new Spinner(topic);
+ phase = Object.freeze({
+ /**
+ * Register a blocker for the completion of a phase.
+ *
+ * @param {string} name The human-readable name of the blocker. Used
+ * for debugging/error reporting. Please make sure that the name
+ * respects the following model: "Some Service: some action in progress" -
+ * for instance "OS.File: flushing all pending I/O";
+ * @param {function|promise|*} condition A condition blocking the
+ * completion of the phase. Generally, this is a function
+ * returning a promise. This function is evaluated during the
+ * phase and the phase is guaranteed to not terminate until the
+ * resulting promise is either resolved or rejected. If
+ * |condition| is not a function but another value |v|, it behaves
+ * as if it were a function returning |v|.
+ * @param {object*} details Optionally, an object with details
+ * that may be useful for error reporting, as a subset of of the following
+ * fields:
+ * - fetchState (strongly recommended) A function returning
+ * information about the current state of the blocker as an
+ * object. Used for providing more details when logging errors or
+ * crashing.
+ * - stack. A string containing stack information. This module can
+ * generally infer stack information if it is not provided.
+ * - lineNumber A number containing the line number for the caller.
+ * This module can generally infer this information if it is not
+ * provided.
+ * - filename A string containing the filename for the caller. This
+ * module can generally infer the information if it is not provided.
+ *
+ * Examples:
+ * AsyncShutdown.profileBeforeChange.addBlocker("Module: just a promise",
+ * promise); // profileBeforeChange will not complete until
+ * // promise is resolved or rejected
+ *
+ * AsyncShutdown.profileBeforeChange.addBlocker("Module: a callback",
+ * function callback() {
+ * // ...
+ * // Execute this code during profileBeforeChange
+ * return promise;
+ * // profileBeforeChange will not complete until promise
+ * // is resolved or rejected
+ * });
+ *
+ * AsyncShutdown.profileBeforeChange.addBlocker("Module: trivial callback",
+ * function callback() {
+ * // ...
+ * // Execute this code during profileBeforeChange
+ * // No specific guarantee about completion of profileBeforeChange
+ * });
+ */
+ addBlocker(name, condition, details = null) {
+ spinner.addBlocker(name, condition, details);
+ },
+ /**
+ * Remove the blocker for a condition.
+ *
+ * If several blockers have been registered for the same
+ * condition, remove all these blockers. If no blocker has been
+ * registered for this condition, this is a noop.
+ *
+ * @return {boolean} true if a blocker has been removed, false
+ * otherwise. Note that a result of false may mean either that
+ * the blocker has never been installed or that the phase has
+ * completed and the blocker has already been resolved.
+ */
+ removeBlocker(condition) {
+ return spinner.removeBlocker(condition);
+ },
+
+ get name() {
+ return spinner.name;
+ },
+
+ get isClosed() {
+ return spinner.isClosed;
+ },
+
+ /**
+ * Trigger the phase without having to broadcast a
+ * notification. For testing purposes only.
+ */
+ get _trigger() {
+ let accepted = Services.prefs.getBoolPref(
+ "toolkit.asyncshutdown.testing",
+ false
+ );
+ if (accepted) {
+ return () => spinner.observe();
+ }
+ return undefined;
+ },
+ });
+ gPhases.set(topic, phase);
+ return phase;
+}
+
+/**
+ * Utility class used to spin the event loop until all blockers for a
+ * Phase are satisfied.
+ *
+ * @param {string} topic The xpcom notification for that phase.
+ */
+function Spinner(topic) {
+ this._barrier = new Barrier(topic);
+ this._topic = topic;
+ Services.obs.addObserver(this, topic);
+}
+
+Spinner.prototype = {
+ /**
+ * Register a new condition for this phase.
+ *
+ * See the documentation of `addBlocker` in property `client`
+ * of instances of `Barrier`.
+ */
+ addBlocker(name, condition, details) {
+ this._barrier.client.addBlocker(name, condition, details);
+ },
+ /**
+ * Remove the blocker for a condition.
+ *
+ * See the documentation of `removeBlocker` in rpoperty `client`
+ * of instances of `Barrier`
+ *
+ * @return {boolean} true if a blocker has been removed, false
+ * otherwise. Note that a result of false may mean either that
+ * the blocker has never been installed or that the phase has
+ * completed and the blocker has already been resolved.
+ */
+ removeBlocker(condition) {
+ return this._barrier.client.removeBlocker(condition);
+ },
+
+ get name() {
+ return this._barrier.client.name;
+ },
+
+ get isClosed() {
+ return this._barrier.client.isClosed;
+ },
+
+ // nsIObserver.observe
+ observe() {
+ let topic = this._topic;
+ debug(`Starting phase ${topic}`);
+ Services.obs.removeObserver(this, topic);
+
+ // Setup the promise that will signal our phase's end.
+ let isPhaseEnd = false;
+ try {
+ this._barrier
+ .wait({
+ warnAfterMS: DELAY_WARNING_MS,
+ crashAfterMS: DELAY_CRASH_MS,
+ })
+ .finally(() => {
+ isPhaseEnd = true;
+ });
+ } catch (ex) {
+ debug("Error waiting for notification");
+ throw ex;
+ }
+
+ // Now, spin the event loop. In case of a hang we will just crash without
+ // ever leaving this loop.
+ debug("Spinning the event loop");
+ Services.tm.spinEventLoopUntil(
+ `AsyncShutdown Spinner for ${topic}`,
+ () => isPhaseEnd
+ );
+
+ debug(`Finished phase ${topic}`);
+ },
+};
+
+/**
+ * A mechanism used to register blockers that prevent some action from
+ * happening.
+ *
+ * An instance of |Barrier| provides a capability |client| that
+ * clients can use to register blockers. The barrier is resolved once
+ * all registered blockers have been resolved. The owner of the
+ * |Barrier| may wait for the resolution of the barrier and obtain
+ * information on which blockers have not been resolved yet.
+ *
+ * @param {string} name The name of the blocker. Used mainly for error-
+ * reporting.
+ */
+function Barrier(name) {
+ if (!name) {
+ throw new TypeError("Instances of Barrier need a (non-empty) name");
+ }
+
+ /**
+ * The set of all Promise for which we need to wait before the barrier
+ * is lifted. Note that this set may be changed while we are waiting.
+ *
+ * Set to `null` once the wait is complete.
+ */
+ this._waitForMe = new PromiseSet();
+
+ /**
+ * A map from conditions, as passed by users during the call to `addBlocker`,
+ * to `promise`, as present in `this._waitForMe`.
+ *
+ * Used to let users perform cleanup through `removeBlocker`.
+ * Set to `null` once the wait is complete.
+ *
+ * Key: condition (any, as passed by user)
+ * Value: promise used as a key in `this._waitForMe`. Note that there is
+ * no guarantee that the key is still present in `this._waitForMe`.
+ */
+ this._conditionToPromise = new Map();
+
+ /**
+ * A map from Promise, as present in `this._waitForMe` or
+ * `this._conditionToPromise`, to information on blockers.
+ *
+ * Key: Promise (as present in this._waitForMe or this._conditionToPromise).
+ * Value: {
+ * trigger: function,
+ * promise,
+ * name,
+ * fetchState: function,
+ * stack,
+ * filename,
+ * lineNumber
+ * };
+ */
+ this._promiseToBlocker = new Map();
+
+ /**
+ * The name of the barrier.
+ */
+ if (typeof name != "string") {
+ throw new TypeError("The name of the barrier must be a string");
+ }
+ this._name = name;
+
+ /**
+ * A cache for the promise returned by wait().
+ */
+ this._promise = null;
+
+ /**
+ * `true` once we have started waiting.
+ */
+ this._isStarted = false;
+
+ /**
+ * `true` once we're done and won't accept any new blockers.
+ */
+ this._isClosed = false;
+
+ /**
+ * The capability of adding blockers. This object may safely be returned
+ * or passed to clients.
+ */
+ this.client = {
+ /**
+ * The name of the barrier owning this client.
+ */
+ get name() {
+ return name;
+ },
+
+ /**
+ * Register a blocker for the completion of this barrier.
+ *
+ * @param {string} name The human-readable name of the blocker. Used
+ * for debugging/error reporting. Please make sure that the name
+ * respects the following model: "Some Service: some action in progress" -
+ * for instance "OS.File: flushing all pending I/O";
+ * @param {function|promise|*} condition A condition blocking the
+ * completion of the phase. Generally, this is a function
+ * returning a promise. This function is evaluated during the
+ * phase and the phase is guaranteed to not terminate until the
+ * resulting promise is either resolved or rejected. If
+ * |condition| is not a function but another value |v|, it behaves
+ * as if it were a function returning |v|.
+ * @param {object*} details Optionally, an object with details
+ * that may be useful for error reporting, as a subset of of the following
+ * fields:
+ * - fetchState (strongly recommended) A function returning
+ * information about the current state of the blocker as an
+ * object. Used for providing more details when logging errors or
+ * crashing.
+ * - stack. A string containing stack information. This module can
+ * generally infer stack information if it is not provided.
+ * - lineNumber A number containing the line number for the caller.
+ * This module can generally infer this information if it is not
+ * provided.
+ * - filename A string containing the filename for the caller. This
+ * module can generally infer the information if it is not provided.
+ */
+ addBlocker: (name, condition, details) => {
+ if (typeof name != "string") {
+ gBrokenAddBlockers.push("No-name blocker");
+ throw new TypeError("Expected a human-readable name as first argument");
+ }
+ if (details && typeof details == "function") {
+ details = {
+ fetchState: details,
+ };
+ } else if (!details) {
+ details = {};
+ }
+ if (typeof details != "object") {
+ gBrokenAddBlockers.push(`${name} - invalid details`);
+ throw new TypeError(
+ "Expected an object as third argument to `addBlocker`, got " + details
+ );
+ }
+ if (!this._waitForMe) {
+ gBrokenAddBlockers.push(`${name} - ${this._name} finished`);
+ throw new Error(
+ `Phase "${this._name}" is finished, it is too late to register completion condition "${name}"`
+ );
+ }
+ debug(`Adding blocker ${name} for phase ${this._name}`);
+
+ try {
+ this.client._internalAddBlocker(name, condition, details);
+ } catch (ex) {
+ gBrokenAddBlockers.push(`${name} - ${ex.message}`);
+ throw ex;
+ }
+ },
+
+ _internalAddBlocker: (
+ name,
+ condition,
+ { fetchState = null, filename = null, lineNumber = null, stack = null }
+ ) => {
+ if (fetchState != null && typeof fetchState != "function") {
+ throw new TypeError("Expected a function for option `fetchState`");
+ }
+
+ // Split the condition between a trigger function and a promise.
+
+ // The function to call to notify the blocker that we have started waiting.
+ // This function returns a promise resolved/rejected once the
+ // condition is complete, and never throws.
+ let trigger;
+
+ // A promise resolved once the condition is complete.
+ let promise;
+ if (typeof condition == "function") {
+ promise = new Promise((resolve, reject) => {
+ trigger = () => {
+ try {
+ resolve(condition());
+ } catch (ex) {
+ reject(ex);
+ }
+ };
+ });
+ } else {
+ // If `condition` is not a function, `trigger` is not particularly
+ // interesting, and `condition` needs to be normalized to a promise.
+ trigger = () => {};
+ promise = Promise.resolve(condition);
+ }
+
+ // Make sure that `promise` never rejects.
+ promise = promise
+ .catch(error => {
+ let msg = `A blocker encountered an error while we were waiting.
+ Blocker: ${name}
+ Phase: ${this._name}
+ State: ${safeGetState(fetchState)}`;
+ warn(msg, error);
+
+ // The error should remain uncaught, to ensure that it
+ // still causes tests to fail.
+ Promise.reject(error);
+ })
+ // Added as a last line of defense, in case `warn`, `this._name` or
+ // `safeGetState` somehow throws an error.
+ .catch(() => {});
+
+ let topFrame = null;
+ if (filename == null || lineNumber == null || stack == null) {
+ topFrame = Components.stack;
+ }
+
+ let blocker = {
+ trigger,
+ promise,
+ name,
+ fetchState,
+ getOrigin: () => getOrigin(topFrame, filename, lineNumber, stack),
+ };
+
+ this._waitForMe.add(promise);
+ this._promiseToBlocker.set(promise, blocker);
+ this._conditionToPromise.set(condition, promise);
+
+ // As conditions may hold lots of memory, we attempt to cleanup
+ // as soon as we are done (which might be in the next tick, if
+ // we have been passed a resolved promise).
+ promise = promise.then(() => {
+ debug(`Completed blocker ${name} for phase ${this._name}`);
+ this._removeBlocker(condition);
+ });
+
+ if (this._isStarted) {
+ // The wait has already started. The blocker should be
+ // notified asap. We do it out of band as clients probably
+ // expect `addBlocker` to return immediately.
+ Promise.resolve().then(trigger);
+ }
+ },
+
+ /**
+ * Remove the blocker for a condition.
+ *
+ * If several blockers have been registered for the same
+ * condition, remove all these blockers. If no blocker has been
+ * registered for this condition, this is a noop.
+ *
+ * @return {boolean} true if at least one blocker has been
+ * removed, false otherwise.
+ */
+ removeBlocker: condition => {
+ return this._removeBlocker(condition);
+ },
+ };
+
+ /**
+ * Whether this client still accepts new blockers.
+ */
+ Object.defineProperty(this.client, "isClosed", {
+ get: () => {
+ return this._isClosed;
+ },
+ });
+}
+Barrier.prototype = Object.freeze({
+ /**
+ * The current state of the barrier, as a JSON-serializable object
+ * designed for error-reporting.
+ */
+ get state() {
+ if (!this._isStarted) {
+ return "Not started";
+ }
+ if (!this._waitForMe) {
+ return "Complete";
+ }
+ let frozen = [];
+ for (let blocker of this._promiseToBlocker.values()) {
+ let { name, fetchState } = blocker;
+ let { stack, filename, lineNumber } = blocker.getOrigin();
+ frozen.push({
+ name,
+ state: safeGetState(fetchState),
+ filename,
+ lineNumber,
+ stack,
+ });
+ }
+ return frozen;
+ },
+
+ /**
+ * Wait until all currently registered blockers are complete.
+ *
+ * Once this method has been called, any attempt to register a new blocker
+ * for this barrier will cause an error.
+ *
+ * Successive calls to this method always return the same value.
+ *
+ * @param {object=} options Optionally, an object that may contain
+ * the following fields:
+ * {number} warnAfterMS If provided and > 0, print a warning if the barrier
+ * has not been resolved after the given number of milliseconds.
+ * {number} crashAfterMS If provided and > 0, crash the process if the barrier
+ * has not been resolved after the give number of milliseconds (rounded up
+ * to the next second). To avoid crashing simply because the computer is busy
+ * or going to sleep, we actually wait for ceil(crashAfterMS/1000) successive
+ * periods of at least one second. Upon crashing, if a crash reporter is present,
+ * prepare a crash report with the state of this barrier.
+ *
+ *
+ * @return {Promise} A promise satisfied once all blockers are complete.
+ */
+ wait(options = {}) {
+ // This method only implements caching on top of _wait()
+ if (this._promise) {
+ return this._promise;
+ }
+ return (this._promise = this._wait(options));
+ },
+ _wait(options) {
+ // Sanity checks
+ if (this._isStarted) {
+ throw new TypeError("Internal error: already started " + this._name);
+ }
+ if (
+ !this._waitForMe ||
+ !this._conditionToPromise ||
+ !this._promiseToBlocker
+ ) {
+ throw new TypeError("Internal error: already finished " + this._name);
+ }
+
+ let topic = this._name;
+
+ // Notify blockers
+ for (let blocker of this._promiseToBlocker.values()) {
+ blocker.trigger(); // We have guarantees that this method will never throw
+ }
+
+ this._isStarted = true;
+
+ // Now, wait
+ let promise = this._waitForMe.wait(() => {
+ this._isClosed = true;
+ });
+
+ promise = promise.catch(function onError(error) {
+ // I don't think that this can happen.
+ // However, let's be overcautious with async/shutdown error reporting.
+ let msg =
+ "An uncaught error appeared while completing the phase." +
+ " Phase: " +
+ topic;
+ warn(msg, error);
+ });
+
+ promise = promise.then(() => {
+ // Cleanup memory
+ this._waitForMe = null;
+ this._promiseToBlocker = null;
+ this._conditionToPromise = null;
+ });
+
+ // Now handle warnings and crashes
+ let warnAfterMS = DELAY_WARNING_MS;
+ if (options && "warnAfterMS" in options) {
+ if (
+ typeof options.warnAfterMS == "number" ||
+ options.warnAfterMS == null
+ ) {
+ // Change the delay or deactivate warnAfterMS
+ warnAfterMS = options.warnAfterMS;
+ } else {
+ throw new TypeError("Wrong option value for warnAfterMS");
+ }
+ }
+
+ if (warnAfterMS && warnAfterMS > 0) {
+ // If the promise takes too long to be resolved/rejected,
+ // we need to notify the user.
+ let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+ timer.initWithCallback(
+ () => {
+ let msg =
+ "At least one completion condition is taking too long to complete." +
+ " Conditions: " +
+ JSON.stringify(this.state) +
+ " Barrier: " +
+ topic;
+ warn(msg);
+ },
+ warnAfterMS,
+ Ci.nsITimer.TYPE_ONE_SHOT
+ );
+
+ promise = promise.then(function onSuccess() {
+ timer.cancel();
+ // As a side-effect, this prevents |timer| from
+ // being garbage-collected too early.
+ });
+ }
+
+ let crashAfterMS = DELAY_CRASH_MS;
+ if (options && "crashAfterMS" in options) {
+ if (
+ typeof options.crashAfterMS == "number" ||
+ options.crashAfterMS == null
+ ) {
+ // Change the delay or deactivate crashAfterMS
+ crashAfterMS = options.crashAfterMS;
+ } else {
+ throw new TypeError("Wrong option value for crashAfterMS");
+ }
+ }
+
+ if (crashAfterMS > 0) {
+ let timeToCrash = null;
+
+ // If after |crashAfterMS| milliseconds (adjusted to take into
+ // account sleep and otherwise busy computer) we have not finished
+ // this shutdown phase, we assume that the shutdown is somehow
+ // frozen, presumably deadlocked. At this stage, the only thing we
+ // can do to avoid leaving the user's computer in an unstable (and
+ // battery-sucking) situation is report the issue and crash.
+ timeToCrash = looseTimer(crashAfterMS);
+ timeToCrash.promise.then(
+ () => {
+ // Report the problem as best as we can, then crash.
+ let state = this.state;
+
+ // If you change the following message, please make sure
+ // that any information on the topic and state appears
+ // within the first 200 characters of the message. This
+ // helps automatically sort oranges.
+ let msg =
+ "AsyncShutdown timeout in " +
+ topic +
+ " Conditions: " +
+ JSON.stringify(state) +
+ " At least one completion condition failed to complete" +
+ " within a reasonable amount of time. Causing a crash to" +
+ " ensure that we do not leave the user with an unresponsive" +
+ " process draining resources.";
+ fatalerr(msg);
+ if (gBrokenAddBlockers.length) {
+ fatalerr(
+ "Broken addBlocker calls: " + JSON.stringify(gBrokenAddBlockers)
+ );
+ }
+ if (Services.appinfo.crashReporterEnabled) {
+ Services.appinfo.annotateCrashReport(
+ "AsyncShutdownTimeout",
+ JSON.stringify(this._gatherCrashReportTimeoutData(topic, state))
+ );
+ } else {
+ warn("No crash reporter available");
+ }
+
+ // To help sorting out bugs, we want to make sure that the
+ // call to nsIDebug2.abort points to a guilty client, rather
+ // than to AsyncShutdown itself. We pick a client that is
+ // still blocking and use its filename/lineNumber,
+ // which have been determined during the call to `addBlocker`.
+ let filename = "?";
+ let lineNumber = -1;
+ for (let blocker of this._promiseToBlocker.values()) {
+ ({ filename, lineNumber } = blocker.getOrigin());
+ break;
+ }
+ lazy.gDebug.abort(filename, lineNumber);
+ },
+ function onSatisfied() {
+ // The promise has been rejected, which means that we have satisfied
+ // all completion conditions.
+ }
+ );
+
+ promise = promise.then(
+ function () {
+ timeToCrash.reject();
+ } /* No error is possible here*/
+ );
+ }
+
+ return promise;
+ },
+
+ _gatherCrashReportTimeoutData(phase, conditions) {
+ let data = { phase, conditions };
+ if (gBrokenAddBlockers.length) {
+ data.brokenAddBlockers = gBrokenAddBlockers;
+ }
+ return data;
+ },
+
+ _removeBlocker(condition) {
+ if (
+ !this._waitForMe ||
+ !this._promiseToBlocker ||
+ !this._conditionToPromise
+ ) {
+ // We have already cleaned up everything.
+ return false;
+ }
+
+ let promise = this._conditionToPromise.get(condition);
+ if (!promise) {
+ // The blocker has already been removed
+ return false;
+ }
+ this._conditionToPromise.delete(condition);
+ this._promiseToBlocker.delete(promise);
+ return this._waitForMe.delete(promise);
+ },
+});
+
+// List of well-known phases
+// Ideally, phases should be registered from the component that decides
+// when they start/stop. For compatibility with existing startup/shutdown
+// mechanisms, we register a few phases here.
+
+// Parent process
+if (!isContent) {
+ AsyncShutdown.profileChangeTeardown = getPhase("profile-change-teardown");
+ AsyncShutdown.profileBeforeChange = getPhase("profile-before-change");
+ AsyncShutdown.sendTelemetry = getPhase("profile-before-change-telemetry");
+}
+
+// Notifications that fire in the parent and content process, but should
+// only have phases in the parent process.
+if (!isContent) {
+ AsyncShutdown.quitApplicationGranted = getPhase("quit-application-granted");
+}
+
+// Don't add a barrier for content-child-shutdown because this
+// makes it easier to cause shutdown hangs.
+
+// All processes
+AsyncShutdown.webWorkersShutdown = getPhase("web-workers-shutdown");
+AsyncShutdown.xpcomWillShutdown = getPhase("xpcom-will-shutdown");
+
+AsyncShutdown.Barrier = Barrier;
+
+Object.freeze(AsyncShutdown);