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// Copyright 2014 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.
package runtime
import (
"runtime/internal/atomic"
"unsafe"
)
type mOS struct {
waitsemacount uint32
}
//go:noescape
//extern lwp_park
func lwp_park(abstime *timespec, unpark int32, hint, unparkhint unsafe.Pointer) int32
//go:noescape
//extern lwp_unpark
func lwp_unpark(lwp int32, hint unsafe.Pointer) int32
//go:nosplit
func semacreate(mp *m) {
}
//go:nosplit
func semasleep(ns int64) int32 {
_g_ := getg()
// Compute sleep deadline.
var tsp *timespec
if ns >= 0 {
var ts timespec
var nsec int32
ns += nanotime()
ts.set_sec(int64(timediv(ns, 1000000000, &nsec)))
ts.set_nsec(nsec)
tsp = &ts
}
for {
v := atomic.Load(&_g_.m.mos.waitsemacount)
if v > 0 {
if atomic.Cas(&_g_.m.mos.waitsemacount, v, v-1) {
return 0 // semaphore acquired
}
continue
}
// Sleep until unparked by semawakeup or timeout.
ret := lwp_park(tsp, 0, unsafe.Pointer(&_g_.m.mos.waitsemacount), nil)
if ret == _ETIMEDOUT {
return -1
}
}
}
//go:nosplit
func semawakeup(mp *m) {
atomic.Xadd(&mp.mos.waitsemacount, 1)
// From NetBSD's _lwp_unpark(2) manual:
// "If the target LWP is not currently waiting, it will return
// immediately upon the next call to _lwp_park()."
ret := lwp_unpark(int32(mp.procid), unsafe.Pointer(&mp.mos.waitsemacount))
if ret != 0 && ret != _ESRCH {
// semawakeup can be called on signal stack.
systemstack(func() {
print("thrwakeup addr=", &mp.mos.waitsemacount, " sem=", mp.mos.waitsemacount, " ret=", ret, "\n")
})
}
}
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