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82 lines
2.0 KiB
Go
82 lines
2.0 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import (
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"runtime/internal/atomic"
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"unsafe"
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)
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type mOS struct {
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waitsemacount uint32
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}
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//go:noescape
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//extern lwp_park
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func lwp_park(ts int32, rel int32, abstime *timespec, unpark int32, hint, unparkhint unsafe.Pointer) int32
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//go:noescape
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//extern lwp_unpark
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func lwp_unpark(lwp int32, hint unsafe.Pointer) int32
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//go:nosplit
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func semacreate(mp *m) {
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}
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//go:nosplit
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func semasleep(ns int64) int32 {
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_g_ := getg()
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// Compute sleep deadline.
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var tsp *timespec
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var ts timespec
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if ns >= 0 {
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var nsec int32
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ts.set_sec(int64(timediv(ns, 1000000000, &nsec)))
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ts.set_nsec(nsec)
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tsp = &ts
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}
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for {
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v := atomic.Load(&_g_.m.mos.waitsemacount)
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if v > 0 {
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if atomic.Cas(&_g_.m.mos.waitsemacount, v, v-1) {
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return 0 // semaphore acquired
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}
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continue
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}
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// Sleep until unparked by semawakeup or timeout.
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ret := lwp_park(_CLOCK_MONOTONIC, _TIMER_RELTIME, tsp, 0, unsafe.Pointer(&_g_.m.waitsemacount), nil)
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if ret == _ETIMEDOUT {
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return -1
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} else if ret == _EINTR && ns >= 0 {
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// Avoid sleeping forever if we keep getting
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// interrupted (for example by the profiling
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// timer). It would be if tsp upon return had the
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// remaining time to sleep, but this is good enough.
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var nsec int32
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ns /= 2
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ts.set_sec(timediv(ns, 1000000000, &nsec))
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ts.set_nsec(nsec)
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}
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}
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}
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//go:nosplit
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func semawakeup(mp *m) {
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atomic.Xadd(&mp.mos.waitsemacount, 1)
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// From NetBSD's _lwp_unpark(2) manual:
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// "If the target LWP is not currently waiting, it will return
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// immediately upon the next call to _lwp_park()."
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ret := lwp_unpark(int32(mp.procid), unsafe.Pointer(&mp.mos.waitsemacount))
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if ret != 0 && ret != _ESRCH {
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// semawakeup can be called on signal stack.
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systemstack(func() {
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print("thrwakeup addr=", &mp.mos.waitsemacount, " sem=", mp.mos.waitsemacount, " ret=", ret, "\n")
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})
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}
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}
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