1 files changed, 75 insertions, 0 deletions
diff --git a/ipc/chromium/src/mojo/core/ports/port_locker.cc b/ipc/chromium/src/mojo/core/ports/port_locker.cc
new file mode 100644
index 0000000000..044a26f143
--- /dev/null
+++ b/ipc/chromium/src/mojo/core/ports/port_locker.cc
@@ -0,0 +1,75 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "mojo/core/ports/port_locker.h"
+
+#include <algorithm>
+
+#include "mojo/core/ports/port.h"
+
+#ifdef DEBUG
+#  include "base/thread_local.h"
+#endif
+
+namespace mojo {
+namespace core {
+namespace ports {
+
+namespace {
+
+#ifdef DEBUG
+void UpdateTLS(PortLocker* old_locker, PortLocker* new_locker) {
+  // Sanity check when DCHECK is on to make sure there is only ever one
+  // PortLocker extant on the current thread.
+  static auto* tls = new base::ThreadLocalPointer<PortLocker>();
+  DCHECK_EQ(old_locker, tls->Get());
+  tls->Set(new_locker);
+}
+#endif
+
+}  // namespace
+
+PortLocker::PortLocker(const PortRef** port_refs, size_t num_ports)
+    : port_refs_(port_refs), num_ports_(num_ports) {
+#ifdef DEBUG
+  UpdateTLS(nullptr, this);
+#endif
+
+  // Sort the ports by address to lock them in a globally consistent order.
+  std::sort(
+      port_refs_, port_refs_ + num_ports_,
+      [](const PortRef* a, const PortRef* b) { return a->port() < b->port(); });
+  for (size_t i = 0; i < num_ports_; ++i) {
+    // TODO(crbug.com/725605): Remove this CHECK.
+    CHECK(port_refs_[i]->port());
+    port_refs_[i]->port()->lock_.Lock();
+  }
+}
+
+PortLocker::~PortLocker() {
+  for (size_t i = 0; i < num_ports_; ++i) {
+    port_refs_[i]->port()->lock_.Unlock();
+  }
+
+#ifdef DEBUG
+  UpdateTLS(this, nullptr);
+#endif
+}
+
+#ifdef DEBUG
+// static
+void PortLocker::AssertNoPortsLockedOnCurrentThread() {
+  // Forces a DCHECK if the TLS PortLocker is anything other than null.
+  UpdateTLS(nullptr, nullptr);
+}
+#endif
+
+SinglePortLocker::SinglePortLocker(const PortRef* port_ref)
+    : port_ref_(port_ref), locker_(&port_ref_, 1) {}
+
+SinglePortLocker::~SinglePortLocker() = default;
+
+}  // namespace ports
+}  // namespace core
+}  // namespace mojo