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// 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 := scheduleCallback(delay)
mp := acquirem()
notes[n] = gp
notesWithTimeout[n] = noteWithTimeout{gp: gp, deadline: deadline}
releasem(mp)
gopark(nil, nil, waitReasonSleep, traceEvNone, 1)
clearScheduledCallback(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 waitingForCallback *g
// sleepUntilCallback puts the current goroutine to sleep until a callback is triggered.
// It is currently only used by the callback routine of the syscall/js package.
//go:linkname sleepUntilCallback syscall/js.sleepUntilCallback
func sleepUntilCallback() {
waitingForCallback = getg()
gopark(nil, nil, waitReasonZero, traceEvNone, 1)
waitingForCallback = nil
}
// pauseSchedulerUntilCallback gets called from the scheduler and pauses the execution
// of Go's WebAssembly code until a callback is triggered. Then it checks for note timeouts
// and resumes goroutines that are waiting for a callback.
func pauseSchedulerUntilCallback() bool {
if waitingForCallback == nil && len(notesWithTimeout) == 0 {
return false
}
pause()
checkTimeouts()
if waitingForCallback != nil {
goready(waitingForCallback, 1)
}
return true
}
// pause pauses the execution of Go's WebAssembly code until a callback is triggered.
func pause()
// scheduleCallback tells the WebAssembly environment to trigger a callback after ms milliseconds.
// It returns a timer id that can be used with clearScheduledCallback.
func scheduleCallback(ms int64) int32
// clearScheduledCallback clears a callback scheduled by scheduleCallback.
func clearScheduledCallback(id int32)
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