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// Copyright 2023 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.
//go:build wasip1
package runtime
// wasm has no support for threads yet. There is no preemption.
// See proposal: https://github.com/WebAssembly/threads
// Waiting for a mutex or timeout is implemented as a busy loop
// while allowing other goroutines to run.
const (
mutex_unlocked = 0
mutex_locked = 1
active_spin = 4
active_spin_cnt = 30
)
func mutexContended(l *mutex) bool {
return false
}
func lock(l *mutex) {
lockWithRank(l, getLockRank(l))
}
func lock2(l *mutex) {
if l.key == mutex_locked {
// wasm is single-threaded so we should never
// observe this.
throw("self deadlock")
}
gp := getg()
if gp.m.locks < 0 {
throw("lock count")
}
gp.m.locks++
l.key = mutex_locked
}
func unlock(l *mutex) {
unlockWithRank(l)
}
func unlock2(l *mutex) {
if l.key == mutex_unlocked {
throw("unlock of unlocked lock")
}
gp := getg()
gp.m.locks--
if gp.m.locks < 0 {
throw("lock count")
}
l.key = mutex_unlocked
}
// One-time notifications.
func noteclear(n *note) {
n.key = 0
}
func notewakeup(n *note) {
if n.key != 0 {
print("notewakeup - double wakeup (", n.key, ")\n")
throw("notewakeup - double wakeup")
}
n.key = 1
}
func notesleep(n *note) {
throw("notesleep not supported by wasi")
}
func notetsleep(n *note, ns int64) bool {
throw("notetsleep not supported by wasi")
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")
}
deadline := nanotime() + ns
for {
if n.key != 0 {
return true
}
if sched_yield() != 0 {
throw("sched_yield failed")
}
Gosched()
if ns >= 0 && nanotime() >= deadline {
return false
}
}
}
func beforeIdle(int64, int64) (*g, bool) {
return nil, false
}
func checkTimeouts() {}
//go:wasmimport wasi_snapshot_preview1 sched_yield
func sched_yield() errno
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