1 files changed, 231 insertions, 0 deletions
diff --git a/js/src/gc/GCParallelTask.cpp b/js/src/gc/GCParallelTask.cpp
new file mode 100644
index 0000000000..029315b119
--- /dev/null
+++ b/js/src/gc/GCParallelTask.cpp
@@ -0,0 +1,231 @@
+/* -*- 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 "gc/GCParallelTask.h"
+
+#include "mozilla/Maybe.h"
+#include "mozilla/TimeStamp.h"
+
+#include "gc/GCContext.h"
+#include "gc/GCInternals.h"
+#include "gc/ParallelWork.h"
+#include "vm/HelperThreadState.h"
+#include "vm/Runtime.h"
+#include "vm/Time.h"
+
+using namespace js;
+using namespace js::gc;
+
+using mozilla::Maybe;
+using mozilla::TimeDuration;
+using mozilla::TimeStamp;
+
+js::GCParallelTask::~GCParallelTask() {
+  // The LinkedListElement destructor will remove us from any list we are part
+  // of without synchronization, so ensure that doesn't happen.
+  MOZ_DIAGNOSTIC_ASSERT(!isInList());
+
+  // Only most-derived classes' destructors may do the join: base class
+  // destructors run after those for derived classes' members, so a join in a
+  // base class can't ensure that the task is done using the members. All we
+  // can do now is check that someone has previously stopped the task.
+  assertIdle();
+}
+
+static bool ShouldMeasureTaskStartDelay() {
+  // We use many tasks during GC so randomly sample a small fraction for the
+  // purposes of recording telemetry.
+  return (rand() % 100) == 0;
+}
+
+void js::GCParallelTask::startWithLockHeld(AutoLockHelperThreadState& lock) {
+  MOZ_ASSERT(CanUseExtraThreads());
+  MOZ_ASSERT(HelperThreadState().isInitialized(lock));
+  assertIdle();
+
+  maybeQueueTime_ = TimeStamp();
+  if (ShouldMeasureTaskStartDelay()) {
+    maybeQueueTime_ = TimeStamp::Now();
+  }
+
+  setDispatched(lock);
+  HelperThreadState().submitTask(this, lock);
+}
+
+void js::GCParallelTask::start() {
+  if (!CanUseExtraThreads()) {
+    runFromMainThread();
+    return;
+  }
+
+  AutoLockHelperThreadState lock;
+  startWithLockHeld(lock);
+}
+
+void js::GCParallelTask::startOrRunIfIdle(AutoLockHelperThreadState& lock) {
+  if (wasStarted(lock)) {
+    return;
+  }
+
+  // Join the previous invocation of the task. This will return immediately
+  // if the thread has never been started.
+  joinWithLockHeld(lock);
+
+  if (!CanUseExtraThreads()) {
+    runFromMainThread(lock);
+    return;
+  }
+
+  startWithLockHeld(lock);
+}
+
+void js::GCParallelTask::cancelAndWait() {
+  MOZ_ASSERT(!isCancelled());
+  cancel_ = true;
+  join();
+  cancel_ = false;
+}
+
+void js::GCParallelTask::join(Maybe<TimeStamp> deadline) {
+  AutoLockHelperThreadState lock;
+  joinWithLockHeld(lock, deadline);
+}
+
+void js::GCParallelTask::joinWithLockHeld(AutoLockHelperThreadState& lock,
+                                          Maybe<TimeStamp> deadline) {
+  // Task has not been started; there's nothing to do.
+  if (isIdle(lock)) {
+    return;
+  }
+
+  if (isDispatched(lock) && deadline.isNothing()) {
+    // If the task was dispatched but has not yet started then cancel the task
+    // and run it from the main thread. This stops us from blocking here when
+    // the helper threads are busy with other tasks.
+    cancelDispatchedTask(lock);
+    runFromMainThread(lock);
+  } else {
+    // Otherwise wait for the task to complete.
+    joinNonIdleTask(deadline, lock);
+  }
+
+  if (isIdle(lock)) {
+    recordDuration();
+  }
+}
+
+void GCParallelTask::recordDuration() {
+  if (phaseKind != gcstats::PhaseKind::NONE) {
+    gc->stats().recordParallelPhase(phaseKind, duration_);
+  }
+}
+
+void js::GCParallelTask::joinNonIdleTask(Maybe<TimeStamp> deadline,
+                                         AutoLockHelperThreadState& lock) {
+  MOZ_ASSERT(!isIdle(lock));
+
+  while (!isFinished(lock)) {
+    TimeDuration timeout = TimeDuration::Forever();
+    if (deadline) {
+      TimeStamp now = TimeStamp::Now();
+      if (*deadline <= now) {
+        break;
+      }
+      timeout = *deadline - now;
+    }
+
+    HelperThreadState().wait(lock, timeout);
+  }
+
+  if (isFinished(lock)) {
+    setIdle(lock);
+  }
+}
+
+void js::GCParallelTask::cancelDispatchedTask(AutoLockHelperThreadState& lock) {
+  MOZ_ASSERT(isDispatched(lock));
+  MOZ_ASSERT(isInList());
+  remove();
+  setIdle(lock);
+}
+
+void js::GCParallelTask::runFromMainThread(AutoLockHelperThreadState& lock) {
+  assertIdle();
+  MOZ_ASSERT(js::CurrentThreadCanAccessRuntime(gc->rt));
+  state_ = State::Running;
+  runTask(gc->rt->gcContext(), lock);
+  state_ = State::Idle;
+}
+
+void js::GCParallelTask::runFromMainThread() {
+  AutoLockHelperThreadState lock;
+  runFromMainThread(lock);
+}
+
+class MOZ_RAII AutoGCContext {
+  JS::GCContext context;
+
+ public:
+  explicit AutoGCContext(JSRuntime* runtime) : context(runtime) {
+    MOZ_RELEASE_ASSERT(TlsGCContext.init(),
+                       "Failed to initialize TLS for GC context");
+
+    MOZ_ASSERT(!TlsGCContext.get());
+    TlsGCContext.set(&context);
+  }
+
+  ~AutoGCContext() {
+    MOZ_ASSERT(TlsGCContext.get() == &context);
+    TlsGCContext.set(nullptr);
+  }
+
+  JS::GCContext* get() { return &context; }
+};
+
+void js::GCParallelTask::runHelperThreadTask(AutoLockHelperThreadState& lock) {
+  setRunning(lock);
+
+  AutoGCContext gcContext(gc->rt);
+
+  runTask(gcContext.get(), lock);
+
+  setFinished(lock);
+}
+
+void GCParallelTask::runTask(JS::GCContext* gcx,
+                             AutoLockHelperThreadState& lock) {
+  // Run the task from either the main thread or a helper thread.
+
+  AutoSetThreadGCUse setUse(gcx, use);
+
+  // The hazard analysis can't tell what the call to func_ will do but it's not
+  // allowed to GC.
+  JS::AutoSuppressGCAnalysis nogc;
+
+  TimeStamp timeStart = TimeStamp::Now();
+  run(lock);
+  duration_ = TimeSince(timeStart);
+
+  if (maybeQueueTime_) {
+    TimeDuration delay = timeStart - maybeQueueTime_;
+    gc->rt->metrics().GC_TASK_START_DELAY_US(delay);
+  }
+}
+
+bool js::GCParallelTask::isIdle() const {
+  AutoLockHelperThreadState lock;
+  return isIdle(lock);
+}
+
+bool js::GCParallelTask::wasStarted() const {
+  AutoLockHelperThreadState lock;
+  return wasStarted(lock);
+}
+
+/* static */
+size_t js::gc::GCRuntime::parallelWorkerCount() const {
+  return std::min(helperThreadCount.ref(), MaxParallelWorkers);
+}