mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-02 18:53:22 +00:00
656 lines
14 KiB
Go
656 lines
14 KiB
Go
// 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
|
|
|
|
// This file contains the implementation of Go channels.
|
|
|
|
import "unsafe"
|
|
|
|
const (
|
|
maxAlign = 8
|
|
hchanSize = unsafe.Sizeof(hchan{}) + uintptr(-int(unsafe.Sizeof(hchan{}))&(maxAlign-1))
|
|
debugChan = false
|
|
)
|
|
|
|
// TODO(khr): make hchan.buf an unsafe.Pointer, not a *uint8
|
|
|
|
func makechan(t *chantype, size int64) *hchan {
|
|
elem := t.elem
|
|
|
|
// compiler checks this but be safe.
|
|
if elem.size >= 1<<16 {
|
|
gothrow("makechan: invalid channel element type")
|
|
}
|
|
if hchanSize%maxAlign != 0 || elem.align > maxAlign {
|
|
gothrow("makechan: bad alignment")
|
|
}
|
|
if size < 0 || int64(uintptr(size)) != size || (elem.size > 0 && uintptr(size) > (maxmem-hchanSize)/uintptr(elem.size)) {
|
|
panic("makechan: size out of range")
|
|
}
|
|
|
|
var c *hchan
|
|
if elem.kind&kindNoPointers != 0 || size == 0 {
|
|
// Allocate memory in one call.
|
|
// Hchan does not contain pointers interesting for GC in this case:
|
|
// buf points into the same allocation, elemtype is persistent.
|
|
// SudoG's are referenced from their owning thread so they can't be collected.
|
|
// TODO(dvyukov,rlh): Rethink when collector can move allocated objects.
|
|
c = (*hchan)(mallocgc(hchanSize+uintptr(size)*uintptr(elem.size), nil, flagNoScan))
|
|
if size > 0 && elem.size != 0 {
|
|
c.buf = (*uint8)(add(unsafe.Pointer(c), hchanSize))
|
|
} else {
|
|
c.buf = (*uint8)(unsafe.Pointer(c)) // race detector uses this location for synchronization
|
|
}
|
|
} else {
|
|
c = new(hchan)
|
|
c.buf = (*uint8)(newarray(elem, uintptr(size)))
|
|
}
|
|
c.elemsize = uint16(elem.size)
|
|
c.elemtype = elem
|
|
c.dataqsiz = uint(size)
|
|
|
|
if debugChan {
|
|
print("makechan: chan=", c, "; elemsize=", elem.size, "; elemalg=", elem.alg, "; dataqsiz=", size, "\n")
|
|
}
|
|
return c
|
|
}
|
|
|
|
// chanbuf(c, i) is pointer to the i'th slot in the buffer.
|
|
func chanbuf(c *hchan, i uint) unsafe.Pointer {
|
|
return add(unsafe.Pointer(c.buf), uintptr(i)*uintptr(c.elemsize))
|
|
}
|
|
|
|
// entry point for c <- x from compiled code
|
|
//go:nosplit
|
|
func chansend1(t *chantype, c *hchan, elem unsafe.Pointer) {
|
|
chansend(t, c, elem, true, getcallerpc(unsafe.Pointer(&t)))
|
|
}
|
|
|
|
/*
|
|
* generic single channel send/recv
|
|
* If block is not nil,
|
|
* then the protocol will not
|
|
* sleep but return if it could
|
|
* not complete.
|
|
*
|
|
* sleep can wake up with g.param == nil
|
|
* when a channel involved in the sleep has
|
|
* been closed. it is easiest to loop and re-run
|
|
* the operation; we'll see that it's now closed.
|
|
*/
|
|
func chansend(t *chantype, c *hchan, ep unsafe.Pointer, block bool, callerpc uintptr) bool {
|
|
if raceenabled {
|
|
raceReadObjectPC(t.elem, ep, callerpc, funcPC(chansend))
|
|
}
|
|
|
|
if c == nil {
|
|
if !block {
|
|
return false
|
|
}
|
|
gopark(nil, nil, "chan send (nil chan)")
|
|
gothrow("unreachable")
|
|
}
|
|
|
|
if debugChan {
|
|
print("chansend: chan=", c, "\n")
|
|
}
|
|
|
|
if raceenabled {
|
|
racereadpc(unsafe.Pointer(c), callerpc, funcPC(chansend))
|
|
}
|
|
|
|
// Fast path: check for failed non-blocking operation without acquiring the lock.
|
|
//
|
|
// After observing that the channel is not closed, we observe that the channel is
|
|
// not ready for sending. Each of these observations is a single word-sized read
|
|
// (first c.closed and second c.recvq.first or c.qcount depending on kind of channel).
|
|
// Because a closed channel cannot transition from 'ready for sending' to
|
|
// 'not ready for sending', even if the channel is closed between the two observations,
|
|
// they imply a moment between the two when the channel was both not yet closed
|
|
// and not ready for sending. We behave as if we observed the channel at that moment,
|
|
// and report that the send cannot proceed.
|
|
//
|
|
// It is okay if the reads are reordered here: if we observe that the channel is not
|
|
// ready for sending and then observe that it is not closed, that implies that the
|
|
// channel wasn't closed during the first observation.
|
|
if !block && c.closed == 0 && ((c.dataqsiz == 0 && c.recvq.first == nil) ||
|
|
(c.dataqsiz > 0 && c.qcount == c.dataqsiz)) {
|
|
return false
|
|
}
|
|
|
|
var t0 int64
|
|
if blockprofilerate > 0 {
|
|
t0 = cputicks()
|
|
}
|
|
|
|
lock(&c.lock)
|
|
if c.closed != 0 {
|
|
unlock(&c.lock)
|
|
panic("send on closed channel")
|
|
}
|
|
|
|
if c.dataqsiz == 0 { // synchronous channel
|
|
sg := c.recvq.dequeue()
|
|
if sg != nil { // found a waiting receiver
|
|
if raceenabled {
|
|
racesync(c, sg)
|
|
}
|
|
unlock(&c.lock)
|
|
|
|
recvg := sg.g
|
|
if sg.elem != nil {
|
|
memmove(unsafe.Pointer(sg.elem), ep, uintptr(c.elemsize))
|
|
sg.elem = nil
|
|
}
|
|
recvg.param = unsafe.Pointer(sg)
|
|
if sg.releasetime != 0 {
|
|
sg.releasetime = cputicks()
|
|
}
|
|
goready(recvg)
|
|
return true
|
|
}
|
|
|
|
if !block {
|
|
unlock(&c.lock)
|
|
return false
|
|
}
|
|
|
|
// no receiver available: block on this channel.
|
|
gp := getg()
|
|
mysg := acquireSudog()
|
|
mysg.releasetime = 0
|
|
if t0 != 0 {
|
|
mysg.releasetime = -1
|
|
}
|
|
mysg.elem = ep
|
|
mysg.waitlink = nil
|
|
gp.waiting = mysg
|
|
mysg.g = gp
|
|
mysg.selectdone = nil
|
|
gp.param = nil
|
|
c.sendq.enqueue(mysg)
|
|
goparkunlock(&c.lock, "chan send")
|
|
|
|
// someone woke us up.
|
|
if mysg != gp.waiting {
|
|
gothrow("G waiting list is corrupted!")
|
|
}
|
|
gp.waiting = nil
|
|
if gp.param == nil {
|
|
if c.closed == 0 {
|
|
gothrow("chansend: spurious wakeup")
|
|
}
|
|
panic("send on closed channel")
|
|
}
|
|
gp.param = nil
|
|
if mysg.releasetime > 0 {
|
|
blockevent(int64(mysg.releasetime)-t0, 2)
|
|
}
|
|
releaseSudog(mysg)
|
|
return true
|
|
}
|
|
|
|
// asynchronous channel
|
|
// wait for some space to write our data
|
|
var t1 int64
|
|
for c.qcount >= c.dataqsiz {
|
|
if !block {
|
|
unlock(&c.lock)
|
|
return false
|
|
}
|
|
gp := getg()
|
|
mysg := acquireSudog()
|
|
mysg.releasetime = 0
|
|
if t0 != 0 {
|
|
mysg.releasetime = -1
|
|
}
|
|
mysg.g = gp
|
|
mysg.elem = nil
|
|
mysg.selectdone = nil
|
|
c.sendq.enqueue(mysg)
|
|
goparkunlock(&c.lock, "chan send")
|
|
|
|
// someone woke us up - try again
|
|
if mysg.releasetime > 0 {
|
|
t1 = mysg.releasetime
|
|
}
|
|
releaseSudog(mysg)
|
|
lock(&c.lock)
|
|
if c.closed != 0 {
|
|
unlock(&c.lock)
|
|
panic("send on closed channel")
|
|
}
|
|
}
|
|
|
|
// write our data into the channel buffer
|
|
if raceenabled {
|
|
raceacquire(chanbuf(c, c.sendx))
|
|
racerelease(chanbuf(c, c.sendx))
|
|
}
|
|
memmove(chanbuf(c, c.sendx), ep, uintptr(c.elemsize))
|
|
c.sendx++
|
|
if c.sendx == c.dataqsiz {
|
|
c.sendx = 0
|
|
}
|
|
c.qcount++
|
|
|
|
// wake up a waiting receiver
|
|
sg := c.recvq.dequeue()
|
|
if sg != nil {
|
|
recvg := sg.g
|
|
unlock(&c.lock)
|
|
if sg.releasetime != 0 {
|
|
sg.releasetime = cputicks()
|
|
}
|
|
goready(recvg)
|
|
} else {
|
|
unlock(&c.lock)
|
|
}
|
|
if t1 > 0 {
|
|
blockevent(t1-t0, 2)
|
|
}
|
|
return true
|
|
}
|
|
|
|
func closechan(c *hchan) {
|
|
if c == nil {
|
|
panic("close of nil channel")
|
|
}
|
|
|
|
lock(&c.lock)
|
|
if c.closed != 0 {
|
|
unlock(&c.lock)
|
|
panic("close of closed channel")
|
|
}
|
|
|
|
if raceenabled {
|
|
callerpc := getcallerpc(unsafe.Pointer(&c))
|
|
racewritepc(unsafe.Pointer(c), callerpc, funcPC(closechan))
|
|
racerelease(unsafe.Pointer(c))
|
|
}
|
|
|
|
c.closed = 1
|
|
|
|
// release all readers
|
|
for {
|
|
sg := c.recvq.dequeue()
|
|
if sg == nil {
|
|
break
|
|
}
|
|
gp := sg.g
|
|
sg.elem = nil
|
|
gp.param = nil
|
|
if sg.releasetime != 0 {
|
|
sg.releasetime = cputicks()
|
|
}
|
|
goready(gp)
|
|
}
|
|
|
|
// release all writers
|
|
for {
|
|
sg := c.sendq.dequeue()
|
|
if sg == nil {
|
|
break
|
|
}
|
|
gp := sg.g
|
|
sg.elem = nil
|
|
gp.param = nil
|
|
if sg.releasetime != 0 {
|
|
sg.releasetime = cputicks()
|
|
}
|
|
goready(gp)
|
|
}
|
|
unlock(&c.lock)
|
|
}
|
|
|
|
// entry points for <- c from compiled code
|
|
//go:nosplit
|
|
func chanrecv1(t *chantype, c *hchan, elem unsafe.Pointer) {
|
|
chanrecv(t, c, elem, true)
|
|
}
|
|
|
|
//go:nosplit
|
|
func chanrecv2(t *chantype, c *hchan, elem unsafe.Pointer) (received bool) {
|
|
_, received = chanrecv(t, c, elem, true)
|
|
return
|
|
}
|
|
|
|
// chanrecv receives on channel c and writes the received data to ep.
|
|
// ep may be nil, in which case received data is ignored.
|
|
// If block == false and no elements are available, returns (false, false).
|
|
// Otherwise, if c is closed, zeros *ep and returns (true, false).
|
|
// Otherwise, fills in *ep with an element and returns (true, true).
|
|
func chanrecv(t *chantype, c *hchan, ep unsafe.Pointer, block bool) (selected, received bool) {
|
|
// raceenabled: don't need to check ep, as it is always on the stack.
|
|
|
|
if debugChan {
|
|
print("chanrecv: chan=", c, "\n")
|
|
}
|
|
|
|
if c == nil {
|
|
if !block {
|
|
return
|
|
}
|
|
gopark(nil, nil, "chan receive (nil chan)")
|
|
gothrow("unreachable")
|
|
}
|
|
|
|
// Fast path: check for failed non-blocking operation without acquiring the lock.
|
|
//
|
|
// After observing that the channel is not ready for receiving, we observe that the
|
|
// channel is not closed. Each of these observations is a single word-sized read
|
|
// (first c.sendq.first or c.qcount, and second c.closed).
|
|
// Because a channel cannot be reopened, the later observation of the channel
|
|
// being not closed implies that it was also not closed at the moment of the
|
|
// first observation. We behave as if we observed the channel at that moment
|
|
// and report that the receive cannot proceed.
|
|
//
|
|
// The order of operations is important here: reversing the operations can lead to
|
|
// incorrect behavior when racing with a close.
|
|
if !block && (c.dataqsiz == 0 && c.sendq.first == nil ||
|
|
c.dataqsiz > 0 && atomicloaduint(&c.qcount) == 0) &&
|
|
atomicload(&c.closed) == 0 {
|
|
return
|
|
}
|
|
|
|
var t0 int64
|
|
if blockprofilerate > 0 {
|
|
t0 = cputicks()
|
|
}
|
|
|
|
lock(&c.lock)
|
|
if c.dataqsiz == 0 { // synchronous channel
|
|
if c.closed != 0 {
|
|
return recvclosed(c, ep)
|
|
}
|
|
|
|
sg := c.sendq.dequeue()
|
|
if sg != nil {
|
|
if raceenabled {
|
|
racesync(c, sg)
|
|
}
|
|
unlock(&c.lock)
|
|
|
|
if ep != nil {
|
|
memmove(ep, sg.elem, uintptr(c.elemsize))
|
|
}
|
|
sg.elem = nil
|
|
gp := sg.g
|
|
gp.param = unsafe.Pointer(sg)
|
|
if sg.releasetime != 0 {
|
|
sg.releasetime = cputicks()
|
|
}
|
|
goready(gp)
|
|
selected = true
|
|
received = true
|
|
return
|
|
}
|
|
|
|
if !block {
|
|
unlock(&c.lock)
|
|
return
|
|
}
|
|
|
|
// no sender available: block on this channel.
|
|
gp := getg()
|
|
mysg := acquireSudog()
|
|
mysg.releasetime = 0
|
|
if t0 != 0 {
|
|
mysg.releasetime = -1
|
|
}
|
|
mysg.elem = ep
|
|
mysg.waitlink = nil
|
|
gp.waiting = mysg
|
|
mysg.g = gp
|
|
mysg.selectdone = nil
|
|
gp.param = nil
|
|
c.recvq.enqueue(mysg)
|
|
goparkunlock(&c.lock, "chan receive")
|
|
|
|
// someone woke us up
|
|
if mysg != gp.waiting {
|
|
gothrow("G waiting list is corrupted!")
|
|
}
|
|
gp.waiting = nil
|
|
if mysg.releasetime > 0 {
|
|
blockevent(mysg.releasetime-t0, 2)
|
|
}
|
|
haveData := gp.param != nil
|
|
gp.param = nil
|
|
releaseSudog(mysg)
|
|
|
|
if haveData {
|
|
// a sender sent us some data. It already wrote to ep.
|
|
selected = true
|
|
received = true
|
|
return
|
|
}
|
|
|
|
lock(&c.lock)
|
|
if c.closed == 0 {
|
|
gothrow("chanrecv: spurious wakeup")
|
|
}
|
|
return recvclosed(c, ep)
|
|
}
|
|
|
|
// asynchronous channel
|
|
// wait for some data to appear
|
|
var t1 int64
|
|
for c.qcount <= 0 {
|
|
if c.closed != 0 {
|
|
selected, received = recvclosed(c, ep)
|
|
if t1 > 0 {
|
|
blockevent(t1-t0, 2)
|
|
}
|
|
return
|
|
}
|
|
|
|
if !block {
|
|
unlock(&c.lock)
|
|
return
|
|
}
|
|
|
|
// wait for someone to send an element
|
|
gp := getg()
|
|
mysg := acquireSudog()
|
|
mysg.releasetime = 0
|
|
if t0 != 0 {
|
|
mysg.releasetime = -1
|
|
}
|
|
mysg.elem = nil
|
|
mysg.g = gp
|
|
mysg.selectdone = nil
|
|
|
|
c.recvq.enqueue(mysg)
|
|
goparkunlock(&c.lock, "chan receive")
|
|
|
|
// someone woke us up - try again
|
|
if mysg.releasetime > 0 {
|
|
t1 = mysg.releasetime
|
|
}
|
|
releaseSudog(mysg)
|
|
lock(&c.lock)
|
|
}
|
|
|
|
if raceenabled {
|
|
raceacquire(chanbuf(c, c.recvx))
|
|
racerelease(chanbuf(c, c.recvx))
|
|
}
|
|
if ep != nil {
|
|
memmove(ep, chanbuf(c, c.recvx), uintptr(c.elemsize))
|
|
}
|
|
memclr(chanbuf(c, c.recvx), uintptr(c.elemsize))
|
|
|
|
c.recvx++
|
|
if c.recvx == c.dataqsiz {
|
|
c.recvx = 0
|
|
}
|
|
c.qcount--
|
|
|
|
// ping a sender now that there is space
|
|
sg := c.sendq.dequeue()
|
|
if sg != nil {
|
|
gp := sg.g
|
|
unlock(&c.lock)
|
|
if sg.releasetime != 0 {
|
|
sg.releasetime = cputicks()
|
|
}
|
|
goready(gp)
|
|
} else {
|
|
unlock(&c.lock)
|
|
}
|
|
|
|
if t1 > 0 {
|
|
blockevent(t1-t0, 2)
|
|
}
|
|
selected = true
|
|
received = true
|
|
return
|
|
}
|
|
|
|
// recvclosed is a helper function for chanrecv. Handles cleanup
|
|
// when the receiver encounters a closed channel.
|
|
// Caller must hold c.lock, recvclosed will release the lock.
|
|
func recvclosed(c *hchan, ep unsafe.Pointer) (selected, recevied bool) {
|
|
if raceenabled {
|
|
raceacquire(unsafe.Pointer(c))
|
|
}
|
|
unlock(&c.lock)
|
|
if ep != nil {
|
|
memclr(ep, uintptr(c.elemsize))
|
|
}
|
|
return true, false
|
|
}
|
|
|
|
// compiler implements
|
|
//
|
|
// select {
|
|
// case c <- v:
|
|
// ... foo
|
|
// default:
|
|
// ... bar
|
|
// }
|
|
//
|
|
// as
|
|
//
|
|
// if selectnbsend(c, v) {
|
|
// ... foo
|
|
// } else {
|
|
// ... bar
|
|
// }
|
|
//
|
|
func selectnbsend(t *chantype, c *hchan, elem unsafe.Pointer) (selected bool) {
|
|
return chansend(t, c, elem, false, getcallerpc(unsafe.Pointer(&t)))
|
|
}
|
|
|
|
// compiler implements
|
|
//
|
|
// select {
|
|
// case v = <-c:
|
|
// ... foo
|
|
// default:
|
|
// ... bar
|
|
// }
|
|
//
|
|
// as
|
|
//
|
|
// if selectnbrecv(&v, c) {
|
|
// ... foo
|
|
// } else {
|
|
// ... bar
|
|
// }
|
|
//
|
|
func selectnbrecv(t *chantype, elem unsafe.Pointer, c *hchan) (selected bool) {
|
|
selected, _ = chanrecv(t, c, elem, false)
|
|
return
|
|
}
|
|
|
|
// compiler implements
|
|
//
|
|
// select {
|
|
// case v, ok = <-c:
|
|
// ... foo
|
|
// default:
|
|
// ... bar
|
|
// }
|
|
//
|
|
// as
|
|
//
|
|
// if c != nil && selectnbrecv2(&v, &ok, c) {
|
|
// ... foo
|
|
// } else {
|
|
// ... bar
|
|
// }
|
|
//
|
|
func selectnbrecv2(t *chantype, elem unsafe.Pointer, received *bool, c *hchan) (selected bool) {
|
|
// TODO(khr): just return 2 values from this function, now that it is in Go.
|
|
selected, *received = chanrecv(t, c, elem, false)
|
|
return
|
|
}
|
|
|
|
func reflect_chansend(t *chantype, c *hchan, elem unsafe.Pointer, nb bool) (selected bool) {
|
|
return chansend(t, c, elem, !nb, getcallerpc(unsafe.Pointer(&t)))
|
|
}
|
|
|
|
func reflect_chanrecv(t *chantype, c *hchan, nb bool, elem unsafe.Pointer) (selected bool, received bool) {
|
|
return chanrecv(t, c, elem, !nb)
|
|
}
|
|
|
|
func reflect_chanlen(c *hchan) int {
|
|
if c == nil {
|
|
return 0
|
|
}
|
|
return int(c.qcount)
|
|
}
|
|
|
|
func reflect_chancap(c *hchan) int {
|
|
if c == nil {
|
|
return 0
|
|
}
|
|
return int(c.dataqsiz)
|
|
}
|
|
|
|
func (q *waitq) enqueue(sgp *sudog) {
|
|
sgp.next = nil
|
|
if q.first == nil {
|
|
q.first = sgp
|
|
q.last = sgp
|
|
return
|
|
}
|
|
q.last.next = sgp
|
|
q.last = sgp
|
|
}
|
|
|
|
func (q *waitq) dequeue() *sudog {
|
|
for {
|
|
sgp := q.first
|
|
if sgp == nil {
|
|
return nil
|
|
}
|
|
q.first = sgp.next
|
|
sgp.next = nil
|
|
if q.last == sgp {
|
|
q.last = nil
|
|
}
|
|
|
|
// if sgp participates in a select and is already signaled, ignore it
|
|
if sgp.selectdone != nil {
|
|
// claim the right to signal
|
|
if *sgp.selectdone != 0 || !cas(sgp.selectdone, 0, 1) {
|
|
continue
|
|
}
|
|
}
|
|
|
|
return sgp
|
|
}
|
|
}
|
|
|
|
func racesync(c *hchan, sg *sudog) {
|
|
racerelease(chanbuf(c, 0))
|
|
raceacquireg(sg.g, chanbuf(c, 0))
|
|
racereleaseg(sg.g, chanbuf(c, 0))
|
|
raceacquire(chanbuf(c, 0))
|
|
}
|