1 files changed, 255 insertions, 0 deletions
diff --git a/xpcom/threads/IdlePeriodState.cpp b/xpcom/threads/IdlePeriodState.cpp
new file mode 100644
index 0000000000..ca7f15321f
--- /dev/null
+++ b/xpcom/threads/IdlePeriodState.cpp
@@ -0,0 +1,255 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/IdlePeriodState.h"
+#include "mozilla/StaticPrefs_idle_period.h"
+#include "mozilla/ipc/IdleSchedulerChild.h"
+#include "nsIIdlePeriod.h"
+#include "nsThreadManager.h"
+#include "nsThreadUtils.h"
+#include "nsXPCOM.h"
+#include "nsXULAppAPI.h"
+
+static uint64_t sIdleRequestCounter = 0;
+
+namespace mozilla {
+
+IdlePeriodState::IdlePeriodState(already_AddRefed<nsIIdlePeriod>&& aIdlePeriod)
+    : mIdlePeriod(aIdlePeriod) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+}
+
+IdlePeriodState::~IdlePeriodState() {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+  if (mIdleScheduler) {
+    mIdleScheduler->Disconnect();
+  }
+}
+
+size_t IdlePeriodState::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+  size_t n = 0;
+  if (mIdlePeriod) {
+    n += aMallocSizeOf(mIdlePeriod);
+  }
+
+  return n;
+}
+
+void IdlePeriodState::FlagNotIdle() {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+
+  EnsureIsActive();
+  if (mIdleToken && mIdleToken < TimeStamp::Now()) {
+    ClearIdleToken();
+  }
+}
+
+void IdlePeriodState::RanOutOfTasks(const MutexAutoUnlock& aProofOfUnlock) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+  MOZ_ASSERT(!mHasPendingEventsPromisedIdleEvent);
+  EnsureIsPaused(aProofOfUnlock);
+  ClearIdleToken();
+}
+
+TimeStamp IdlePeriodState::GetIdleDeadlineInternal(
+    bool aIsPeek, const MutexAutoUnlock& aProofOfUnlock) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+
+  bool shuttingDown;
+  TimeStamp localIdleDeadline =
+      GetLocalIdleDeadline(shuttingDown, aProofOfUnlock);
+  if (!localIdleDeadline) {
+    if (!aIsPeek) {
+      EnsureIsPaused(aProofOfUnlock);
+      ClearIdleToken();
+    }
+    return TimeStamp();
+  }
+
+  TimeStamp idleDeadline =
+      mHasPendingEventsPromisedIdleEvent || shuttingDown
+          ? localIdleDeadline
+          : GetIdleToken(localIdleDeadline, aProofOfUnlock);
+  if (!idleDeadline) {
+    if (!aIsPeek) {
+      EnsureIsPaused(aProofOfUnlock);
+
+      // Don't call ClearIdleToken() here, since we may have a pending
+      // request already.
+      //
+      // RequestIdleToken can do all sorts of IPC stuff that might
+      // take mutexes.  This is one reason why we need the
+      // MutexAutoUnlock reference!
+      RequestIdleToken(localIdleDeadline);
+    }
+    return TimeStamp();
+  }
+
+  if (!aIsPeek) {
+    EnsureIsActive();
+  }
+  return idleDeadline;
+}
+
+TimeStamp IdlePeriodState::GetLocalIdleDeadline(
+    bool& aShuttingDown, const MutexAutoUnlock& aProofOfUnlock) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+  // If we are shutting down, we won't honor the idle period, and we will
+  // always process idle runnables.  This will ensure that the idle queue
+  // gets exhausted at shutdown time to prevent intermittently leaking
+  // some runnables inside that queue and even worse potentially leaving
+  // some important cleanup work unfinished.
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdownThreads) ||
+      nsThreadManager::get().GetCurrentThread()->ShuttingDown()) {
+    aShuttingDown = true;
+    return TimeStamp::Now();
+  }
+
+  aShuttingDown = false;
+  TimeStamp idleDeadline;
+  // This GetIdlePeriodHint() call is the reason we need a MutexAutoUnlock here.
+  mIdlePeriod->GetIdlePeriodHint(&idleDeadline);
+
+  // If HasPendingEvents() has been called and it has returned true because of
+  // pending idle events, there is a risk that we may decide here that we aren't
+  // idle and return null, in which case HasPendingEvents() has effectively
+  // lied.  Since we can't go back and fix the past, we have to adjust what we
+  // do here and forcefully pick the idle queue task here.  Note that this means
+  // that we are choosing to run a task from the idle queue when we would
+  // normally decide that we aren't in an idle period, but this can only happen
+  // if we fall out of the idle period in between the call to HasPendingEvents()
+  // and here, which should hopefully be quite rare.  We are effectively
+  // choosing to prioritize the sanity of our API semantics over the optimal
+  // scheduling.
+  if (!mHasPendingEventsPromisedIdleEvent &&
+      (!idleDeadline || idleDeadline < TimeStamp::Now())) {
+    return TimeStamp();
+  }
+  if (mHasPendingEventsPromisedIdleEvent && !idleDeadline) {
+    // If HasPendingEvents() has been called and it has returned true, but we're
+    // no longer in the idle period, we must return a valid timestamp to pretend
+    // that we are still in the idle period.
+    return TimeStamp::Now();
+  }
+  return idleDeadline;
+}
+
+TimeStamp IdlePeriodState::GetIdleToken(TimeStamp aLocalIdlePeriodHint,
+                                        const MutexAutoUnlock& aProofOfUnlock) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+
+  if (!ShouldGetIdleToken()) {
+    return aLocalIdlePeriodHint;
+  }
+
+  if (mIdleToken) {
+    TimeStamp now = TimeStamp::Now();
+    if (mIdleToken < now) {
+      ClearIdleToken();
+      return mIdleToken;
+    }
+    return mIdleToken < aLocalIdlePeriodHint ? mIdleToken
+                                             : aLocalIdlePeriodHint;
+  }
+  return TimeStamp();
+}
+
+void IdlePeriodState::RequestIdleToken(TimeStamp aLocalIdlePeriodHint) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+  MOZ_ASSERT(!mActive);
+
+  if (!mIdleSchedulerInitialized) {
+    mIdleSchedulerInitialized = true;
+    if (ShouldGetIdleToken()) {
+      // For now cross-process idle scheduler is supported only on the main
+      // threads of the child processes.
+      mIdleScheduler = ipc::IdleSchedulerChild::GetMainThreadIdleScheduler();
+      if (mIdleScheduler) {
+        mIdleScheduler->Init(this);
+      }
+    }
+  }
+
+  if (mIdleScheduler && !mIdleRequestId) {
+    TimeStamp now = TimeStamp::Now();
+    if (aLocalIdlePeriodHint <= now) {
+      return;
+    }
+
+    mIdleRequestId = ++sIdleRequestCounter;
+    mIdleScheduler->SendRequestIdleTime(mIdleRequestId,
+                                        aLocalIdlePeriodHint - now);
+  }
+}
+
+void IdlePeriodState::SetIdleToken(uint64_t aId, TimeDuration aDuration) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+
+  // We check the request ID.  It's possible that the server may be granting a
+  // an ealier request that the client has since cancelled and re-requested.
+  if (mIdleRequestId == aId) {
+    mIdleToken = TimeStamp::Now() + aDuration;
+  }
+}
+
+void IdlePeriodState::SetActive() {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+  MOZ_ASSERT(!mActive);
+  if (mIdleScheduler) {
+    mIdleScheduler->SetActive();
+  }
+  mActive = true;
+}
+
+void IdlePeriodState::SetPaused(const MutexAutoUnlock& aProofOfUnlock) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+  MOZ_ASSERT(mActive);
+  if (mIdleScheduler && mIdleScheduler->SetPaused()) {
+    // We may have gotten a free cpu core for running idle tasks.
+    // We don't try to catch the case when there are prioritized processes
+    // running.
+
+    // This SendSchedule call is why we need the MutexAutoUnlock here, because
+    // IPC can do weird things with mutexes.
+    mIdleScheduler->SendSchedule();
+  }
+  mActive = false;
+}
+
+void IdlePeriodState::ClearIdleToken() {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Why are we touching idle state off the main thread?");
+
+  if (mIdleRequestId) {
+    if (mIdleScheduler) {
+      // This SendIdleTimeUsed call is why we need to not be holding
+      // any locks here, because IPC can do weird things with mutexes.
+      // Ideally we'd have a MutexAutoUnlock& reference here, but some
+      // callers end up here while just not holding any locks at all.
+      mIdleScheduler->SendIdleTimeUsed(mIdleRequestId);
+    }
+    mIdleRequestId = 0;
+    mIdleToken = TimeStamp();
+  }
+}
+
+bool IdlePeriodState::ShouldGetIdleToken() {
+  return StaticPrefs::idle_period_cross_process_scheduling() &&
+         XRE_IsContentProcess();
+}
+}  // namespace mozilla