1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
// Copyright 2016 The Chromium Authors
// 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/check.h"
namespace mojo {
namespace core {
namespace {
constinit thread_local RequestContext* current_context = nullptr;
} // namespace
RequestContext::RequestContext() : RequestContext(Source::LOCAL_API_CALL) {}
RequestContext::RequestContext(Source source) : source_(source) {
// We allow nested RequestContexts to exist as long as they aren't actually
// used for anything.
if (!current_context) {
current_context = this;
}
}
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.
current_context = nullptr;
MojoTrapEventFlags flags = MOJO_TRAP_EVENT_FLAG_NONE;
if (source_ == Source::LOCAL_API_CALL)
flags |= MOJO_TRAP_EVENT_FLAG_WITHIN_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_) {
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_) {
RequestContext inner_context(source_);
watch.watch->InvokeCallback(watch.result, watch.state, flags);
}
} else {
// It should be impossible for nested contexts to have finalizers.
DCHECK(watch_notify_finalizers_.empty());
DCHECK(watch_cancel_finalizers_.empty());
}
}
// static
RequestContext* RequestContext::current() {
DCHECK(current_context);
return current_context;
}
void RequestContext::AddWatchNotifyFinalizer(scoped_refptr<Watch> watch,
MojoResult result,
const HandleSignalsState& state) {
DCHECK(IsCurrent());
watch_notify_finalizers_.push_back(
WatchNotifyFinalizer(std::move(watch), result, state));
}
void RequestContext::AddWatchCancelFinalizer(scoped_refptr<Watch> watch) {
DCHECK(IsCurrent());
watch_cancel_finalizers_.push_back(std::move(watch));
}
bool RequestContext::IsCurrent() const {
return current_context == this;
}
RequestContext::WatchNotifyFinalizer::WatchNotifyFinalizer(
scoped_refptr<Watch> watch,
MojoResult result,
const HandleSignalsState& state)
: watch(std::move(watch)), result(result), state(state) {}
RequestContext::WatchNotifyFinalizer::WatchNotifyFinalizer(
const WatchNotifyFinalizer& other) = default;
RequestContext::WatchNotifyFinalizer::~WatchNotifyFinalizer() = default;
} // namespace core
} // namespace mojo
|
