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