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// Copyright 2016 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/request_context.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/threading/thread_local.h"
namespace mojo {
namespace core {
namespace {
g_current_context = LAZY_INSTANCE_INITIALIZER;
} // namespace
RequestContext::RequestContext() : RequestContext(Source::LOCAL_API_CALL) {}
RequestContext::RequestContext(Source source)
: source_(source), tls_context_(g_current_context.Pointer()) {
// We allow nested RequestContexts to exist as long as they aren't actually
// used for anything.
if (!tls_context_->Get())
RequestContext::~RequestContext() {
if (IsCurrent()) {
// NOTE: Callbacks invoked by this destructor are allowed to initiate new
// EDK requests on this thread, so we need to reset the thread-local context
// pointer before calling them. We persist the original notification source
// since we're starting over at the bottom of the stack.
MojoTrapEventFlags flags = MOJO_TRAP_EVENT_FLAG_NONE;
if (source_ == Source::LOCAL_API_CALL)
// We send all cancellation notifications first. This is necessary because
// it's possible that cancelled watches have other pending notifications
// attached to this RequestContext.
// From the application's perspective the watch is cancelled as soon as this
// notification is received, and dispatching the cancellation notification
// updates some internal Watch state to ensure no further notifications
// fire. Because notifications on a single Watch are mutually exclusive,
// this is sufficient to guarantee that MOJO_RESULT_CANCELLED is the last
// notification received; which is the guarantee the API makes.
for (const scoped_refptr<Watch>& watch :
watch_cancel_finalizers_.container()) {
static const HandleSignalsState closed_state = {0, 0};
// Establish a new RequestContext to capture and run any new notifications
// triggered by the callback invocation. Note that while it would be safe
// to inherit |source_| from the perspective of Mojo core re-entrancy,
// upper application layers may use the flag as a signal to allow
// synchronous event dispatch and in turn shoot themselves in the foot
// with e.g. mutually recursive event handlers. We avoid that by
// treating all nested trap events as if they originated from a local API
// call even if this is a system RequestContext.
RequestContext inner_context(Source::LOCAL_API_CALL);
watch->InvokeCallback(MOJO_RESULT_CANCELLED, closed_state, flags);
for (const WatchNotifyFinalizer& watch :
watch_notify_finalizers_.container()) {
RequestContext inner_context(source_);>InvokeCallback(watch.result, watch.state, flags);
} else {
// It should be impossible for nested contexts to have finalizers.
// static
RequestContext* RequestContext::current() {
return g_current_context.Pointer()->Get();
void RequestContext::AddWatchNotifyFinalizer(scoped_refptr<Watch> watch,
MojoResult result,
const HandleSignalsState& state) {
WatchNotifyFinalizer(std::move(watch), result, state));
void RequestContext::AddWatchCancelFinalizer(scoped_refptr<Watch> watch) {
bool RequestContext::IsCurrent() const {
return tls_context_->Get() == this;
scoped_refptr<Watch> watch,
MojoResult result,
const HandleSignalsState& state)
: watch(std::move(watch)), result(result), state(state) {}
const WatchNotifyFinalizer& other) = default;
RequestContext::WatchNotifyFinalizer::~WatchNotifyFinalizer() {}
} // namespace core
} // namespace mojo