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
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build js,wasm
package runtime
import (
_ "unsafe"
)
// js/wasm has no support for threads yet. There is no preemption.
// Waiting for a mutex is implemented by allowing other goroutines
// to run until the mutex gets unlocked.
const (
mutex_unlocked = 0
mutex_locked = 1
note_cleared = 0
note_woken = 1
note_timeout = 2
active_spin = 4
active_spin_cnt = 30
passive_spin = 1
)
func lock(l *mutex) {
for l.key == mutex_locked {
mcall(gosched_m)
}
l.key = mutex_locked
}
func unlock(l *mutex) {
if l.key == mutex_unlocked {
throw("unlock of unlocked lock")
}
l.key = mutex_unlocked
}
// One-time notifications.
type noteWithTimeout struct {
gp *g
deadline int64
}
var (
notes = make(map[*note]*g)
notesWithTimeout = make(map[*note]noteWithTimeout)
)
func noteclear(n *note) {
n.key = note_cleared
}
func notewakeup(n *note) {
// gp := getg()
if n.key == note_woken {
throw("notewakeup - double wakeup")
}
cleared := n.key == note_cleared
n.key = note_woken
if cleared {
goready(notes[n], 1)
}
}
func notesleep(n *note) {
throw("notesleep not supported by js")
}
func notetsleep(n *note, ns int64) bool {
throw("notetsleep not supported by js")
return false
}
// same as runtime·notetsleep, but called on user g (not g0)
func notetsleepg(n *note, ns int64) bool {
gp := getg()
if gp == gp.m.g0 {
throw("notetsleepg on g0")
}
if ns >= 0 {
deadline := nanotime() + ns
delay := ns/1000000 + 1 // round up
if delay > 1<<31-1 {
delay = 1<<31 - 1 // cap to max int32
}
id := scheduleTimeoutEvent(delay)
mp := acquirem()
notes[n] = gp
notesWithTimeout[n] = noteWithTimeout{gp: gp, deadline: deadline}
releasem(mp)
gopark(nil, nil, waitReasonSleep, traceEvNone, 1)
clearTimeoutEvent(id) // note might have woken early, clear timeout
mp = acquirem()
delete(notes, n)
delete(notesWithTimeout, n)
releasem(mp)
return n.key == note_woken
}
for n.key != note_woken {
mp := acquirem()
notes[n] = gp
releasem(mp)
gopark(nil, nil, waitReasonZero, traceEvNone, 1)
mp = acquirem()
delete(notes, n)
releasem(mp)
}
return true
}
// checkTimeouts resumes goroutines that are waiting on a note which has reached its deadline.
func checkTimeouts() {
now := nanotime()
for n, nt := range notesWithTimeout {
if n.key == note_cleared && now >= nt.deadline {
n.key = note_timeout
goready(nt.gp, 1)
}
}
}
var returnedEventHandler *g
func init() {
// At the toplevel we need an extra goroutine that handles asynchronous events.
initg := getg()
go func() {
returnedEventHandler = getg()
goready(initg, 1)
gopark(nil, nil, waitReasonZero, traceEvNone, 1)
returnedEventHandler = nil
pause(getcallersp() - 16)
}()
gopark(nil, nil, waitReasonZero, traceEvNone, 1)
}
// beforeIdle gets called by the scheduler if no goroutine is awake.
// We resume the event handler (if available) which will pause the execution.
func beforeIdle() bool {
if returnedEventHandler != nil {
goready(returnedEventHandler, 1)
return true
}
return false
}
// pause sets SP to newsp and pauses the execution of Go's WebAssembly code until an event is triggered.
func pause(newsp uintptr)
// scheduleTimeoutEvent tells the WebAssembly environment to trigger an event after ms milliseconds.
// It returns a timer id that can be used with clearTimeoutEvent.
func scheduleTimeoutEvent(ms int64) int32
// clearTimeoutEvent clears a timeout event scheduled by scheduleTimeoutEvent.
func clearTimeoutEvent(id int32)
func handleEvent() {
prevReturnedEventHandler := returnedEventHandler
returnedEventHandler = nil
checkTimeouts()
eventHandler()
returnedEventHandler = getg()
gopark(nil, nil, waitReasonZero, traceEvNone, 1)
returnedEventHandler = prevReturnedEventHandler
pause(getcallersp() - 16)
}
var eventHandler func()
//go:linkname setEventHandler syscall/js.setEventHandler
func setEventHandler(fn func()) {
eventHandler = fn
}
|
