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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.
package runtime
import "unsafe"
// This is based on the former libgo/runtime/netpoll_select.c implementation
// except that it uses poll instead of select and is written in Go.
// It's also based on Solaris implementation for the arming mechanisms
//go:noescape
//extern poll
func libc_poll(pfds *pollfd, npfds uintptr, timeout uintptr) int32
//go:noescape
//extern pipe
func libc_pipe(fd *int32) int32
//extern __go_fcntl_uintptr
func fcntlUintptr(fd, cmd, arg uintptr) (uintptr, uintptr)
func fcntl(fd, cmd int32, arg uintptr) int32 {
r, _ := fcntlUintptr(uintptr(fd), uintptr(cmd), arg)
return int32(r)
}
// pollfd represents the poll structure for AIX operating system.
type pollfd struct {
fd int32
events int16
revents int16
}
const _POLLIN = 0x0001
const _POLLOUT = 0x0002
const _POLLHUP = 0x2000
const _POLLERR = 0x4000
var (
pfds []pollfd
pds []*pollDesc
mtxpoll mutex
mtxset mutex
rdwake int32
wrwake int32
pendingUpdates int32
)
const pollVerbose = false
func netpollinit() {
var p [2]int32
// Create the pipe we use to wakeup poll.
if err := libc_pipe(&p[0]); err < 0 {
throw("netpollinit: failed to create pipe")
}
rdwake = p[0]
wrwake = p[1]
fl := uintptr(fcntl(rdwake, _F_GETFL, 0))
fcntl(rdwake, _F_SETFL, fl|_O_NONBLOCK)
fcntl(rdwake, _F_SETFD, _FD_CLOEXEC)
fl = uintptr(fcntl(wrwake, _F_GETFL, 0))
fcntl(wrwake, _F_SETFL, fl|_O_NONBLOCK)
fcntl(wrwake, _F_SETFD, _FD_CLOEXEC)
// Pre-allocate array of pollfd structures for poll.
if pollVerbose {
println("*** allocating")
}
pfds = make([]pollfd, 1, 128)
if pollVerbose {
println("*** allocating done", &pfds[0])
}
// Poll the read side of the pipe.
pfds[0].fd = rdwake
pfds[0].events = _POLLIN
pds = make([]*pollDesc, 1, 128)
pds[0] = nil
}
func netpolldescriptor() uintptr {
// Both fd must be returned
if rdwake > 0xFFFF || wrwake > 0xFFFF {
throw("netpolldescriptor: invalid fd number")
}
return uintptr(rdwake<<16 | wrwake)
}
// netpollwakeup writes on wrwake to wakeup poll before any changes.
func netpollwakeup() {
if pendingUpdates == 0 {
pendingUpdates = 1
if pollVerbose {
println("*** writing 1 byte")
}
b := [1]byte{0}
write(uintptr(wrwake), unsafe.Pointer(&b[0]), 1)
}
}
func netpollopen(fd uintptr, pd *pollDesc) int32 {
if pollVerbose {
println("*** netpollopen", fd)
}
lock(&mtxpoll)
netpollwakeup()
lock(&mtxset)
unlock(&mtxpoll)
pd.user = uint32(len(pfds))
pfds = append(pfds, pollfd{fd: int32(fd)})
pds = append(pds, pd)
unlock(&mtxset)
return 0
}
func netpollclose(fd uintptr) int32 {
if pollVerbose {
println("*** netpollclose", fd)
}
lock(&mtxpoll)
netpollwakeup()
lock(&mtxset)
unlock(&mtxpoll)
for i := 0; i < len(pfds); i++ {
if pfds[i].fd == int32(fd) {
pfds[i] = pfds[len(pfds)-1]
pfds = pfds[:len(pfds)-1]
pds[i] = pds[len(pds)-1]
pds[i].user = uint32(i)
pds = pds[:len(pds)-1]
break
}
}
unlock(&mtxset)
return 0
}
func netpollarm(pd *pollDesc, mode int) {
if pollVerbose {
println("*** netpollarm", pd.fd, mode)
}
lock(&mtxpoll)
netpollwakeup()
lock(&mtxset)
unlock(&mtxpoll)
switch mode {
case 'r':
pfds[pd.user].events |= _POLLIN
case 'w':
pfds[pd.user].events |= _POLLOUT
}
unlock(&mtxset)
}
//go:nowritebarrierrec
func netpoll(block bool) gList {
timeout := ^uintptr(0)
if !block {
timeout = 0
return gList{}
}
if pollVerbose {
println("*** netpoll", block)
}
retry:
lock(&mtxpoll)
lock(&mtxset)
pendingUpdates = 0
unlock(&mtxpoll)
if pollVerbose {
println("*** netpoll before poll")
}
n := libc_poll(&pfds[0], uintptr(len(pfds)), timeout)
if pollVerbose {
println("*** netpoll after poll", n)
}
if n < 0 {
e := errno()
if e != _EINTR {
println("errno=", e, " len(pfds)=", len(pfds))
throw("poll failed")
}
if pollVerbose {
println("*** poll failed")
}
unlock(&mtxset)
goto retry
}
// Check if some descriptors need to be changed
if n != 0 && pfds[0].revents&(_POLLIN|_POLLHUP|_POLLERR) != 0 {
var b [1]byte
for read(rdwake, unsafe.Pointer(&b[0]), 1) == 1 {
if pollVerbose {
println("*** read 1 byte from pipe")
}
}
// Do not look at the other fds in this case as the mode may have changed
// XXX only additions of flags are made, so maybe it is ok
unlock(&mtxset)
goto retry
}
var toRun gList
for i := 0; i < len(pfds) && n > 0; i++ {
pfd := &pfds[i]
var mode int32
if pfd.revents&(_POLLIN|_POLLHUP|_POLLERR) != 0 {
mode += 'r'
pfd.events &= ^_POLLIN
}
if pfd.revents&(_POLLOUT|_POLLHUP|_POLLERR) != 0 {
mode += 'w'
pfd.events &= ^_POLLOUT
}
if mode != 0 {
if pollVerbose {
println("*** netpollready i=", i, "revents=", pfd.revents, "events=", pfd.events, "pd=", pds[i])
}
netpollready(&toRun, pds[i], mode)
n--
}
}
unlock(&mtxset)
if block && toRun.empty() {
goto retry
}
if pollVerbose {
println("*** netpoll returning end")
}
return toRun
}
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