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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 "unsafe"
// Solaris runtime-integrated network poller.
// Solaris uses event ports for scalable network I/O. Event
// ports are level-triggered, unlike epoll and kqueue which
// can be configured in both level-triggered and edge-triggered
// mode. Level triggering means we have to keep track of a few things
// ourselves. After we receive an event for a file descriptor,
// it's our responsibility to ask again to be notified for future
// events for that descriptor. When doing this we must keep track of
// what kind of events the goroutines are currently interested in,
// for example a fd may be open both for reading and writing.
// A description of the high level operation of this code
// follows. Networking code will get a file descriptor by some means
// and will register it with the netpolling mechanism by a code path
// that eventually calls runtime·netpollopen. runtime·netpollopen
// calls port_associate with an empty event set. That means that we
// will not receive any events at this point. The association needs
// to be done at this early point because we need to process the I/O
// readiness notification at some point in the future. If I/O becomes
// ready when nobody is listening, when we finally care about it,
// nobody will tell us anymore.
// Beside calling runtime·netpollopen, the networking code paths
// will call runtime·netpollarm each time goroutines are interested
// in doing network I/O. Because now we know what kind of I/O we
// are interested in (reading/writing), we can call port_associate
// passing the correct type of event set (POLLIN/POLLOUT). As we made
// sure to have already associated the file descriptor with the port,
// when we now call port_associate, we will unblock the main poller
// loop (in runtime·netpoll) right away if the socket is actually
// ready for I/O.
// The main poller loop runs in its own thread waiting for events
// using port_getn. When an event happens, it will tell the scheduler
// about it using runtime·netpollready. Besides doing this, it must
// also re-associate the events that were not part of this current
// notification with the file descriptor. Failing to do this would
// mean each notification will prevent concurrent code using the
// same file descriptor in parallel.
// The logic dealing with re-associations is encapsulated in
// runtime·netpollupdate. This function takes care to associate the
// descriptor only with the subset of events that were previously
// part of the association, except the one that just happened. We
// can't re-associate with that right away, because event ports
// are level triggered so it would cause a busy loop. Instead, that
// association is effected only by the runtime·netpollarm code path,
// when Go code actually asks for I/O.
// The open and arming mechanisms are serialized using the lock
// inside PollDesc. This is required because the netpoll loop runs
// asynchronously in respect to other Go code and by the time we get
// to call port_associate to update the association in the loop, the
// file descriptor might have been closed and reopened already. The
// lock allows runtime·netpollupdate to be called synchronously from
// the loop thread while preventing other threads operating to the
// same PollDesc, so once we unblock in the main loop, until we loop
// again we know for sure we are always talking about the same file
// descriptor and can safely access the data we want (the event set).
//go:cgo_import_dynamic libc_port_create port_create ""
//go:cgo_import_dynamic libc_port_associate port_associate ""
//go:cgo_import_dynamic libc_port_dissociate port_dissociate ""
//go:cgo_import_dynamic libc_port_getn port_getn ""
//go:linkname libc_port_create libc_port_create
//go:linkname libc_port_associate libc_port_associate
//go:linkname libc_port_dissociate libc_port_dissociate
//go:linkname libc_port_getn libc_port_getn
var (
libc_port_getn libcFunc
func errno() int32 {
return *getg().m.perrno
func fcntl(fd, cmd int32, arg uintptr) int32 {
return int32(sysvicall3(&libc_fcntl, uintptr(fd), uintptr(cmd), arg))
func port_create() int32 {
return int32(sysvicall0(&libc_port_create))
func port_associate(port, source int32, object uintptr, events uint32, user uintptr) int32 {
return int32(sysvicall5(&libc_port_associate, uintptr(port), uintptr(source), object, uintptr(events), user))
func port_dissociate(port, source int32, object uintptr) int32 {
return int32(sysvicall3(&libc_port_dissociate, uintptr(port), uintptr(source), object))
func port_getn(port int32, evs *portevent, max uint32, nget *uint32, timeout *timespec) int32 {
return int32(sysvicall5(&libc_port_getn, uintptr(port), uintptr(unsafe.Pointer(evs)), uintptr(max), uintptr(unsafe.Pointer(nget)), uintptr(unsafe.Pointer(timeout))))
var portfd int32 = -1
func netpollinit() {
portfd = port_create()
if portfd >= 0 {
fcntl(portfd, _F_SETFD, _FD_CLOEXEC)
print("runtime: port_create failed (errno=", errno(), ")\n")
throw("runtime: netpollinit failed")
func netpolldescriptor() uintptr {
return uintptr(portfd)
func netpollopen(fd uintptr, pd *pollDesc) int32 {
// We don't register for any specific type of events yet, that's
// netpollarm's job. We merely ensure we call port_associate before
// asynchronous connect/accept completes, so when we actually want
// to do any I/O, the call to port_associate (from netpollarm,
// with the interested event set) will unblock port_getn right away
// because of the I/O readiness notification.
pd.user = 0
r := port_associate(portfd, _PORT_SOURCE_FD, fd, 0, uintptr(unsafe.Pointer(pd)))
return r
func netpollclose(fd uintptr) int32 {
return port_dissociate(portfd, _PORT_SOURCE_FD, fd)
// Updates the association with a new set of interested events. After
// this call, port_getn will return one and only one event for that
// particular descriptor, so this function needs to be called again.
func netpollupdate(pd *pollDesc, set, clear uint32) {
if pd.closing {
old := pd.user
events := (old & ^clear) | set
if old == events {
if events != 0 && port_associate(portfd, _PORT_SOURCE_FD, pd.fd, events, uintptr(unsafe.Pointer(pd))) != 0 {
print("runtime: port_associate failed (errno=", errno(), ")\n")
throw("runtime: netpollupdate failed")
pd.user = events
// subscribe the fd to the port such that port_getn will return one event.
func netpollarm(pd *pollDesc, mode int) {
switch mode {
case 'r':
netpollupdate(pd, _POLLIN, 0)
case 'w':
netpollupdate(pd, _POLLOUT, 0)
throw("runtime: bad mode")
// polls for ready network connections
// returns list of goroutines that become runnable
func netpoll(block bool) gList {
if portfd == -1 {
return gList{}
var wait *timespec
var zero timespec
if !block {
wait = &zero
var events [128]portevent
var n uint32 = 1
if port_getn(portfd, &events[0], uint32(len(events)), &n, wait) < 0 {
if e := errno(); e != _EINTR {
print("runtime: port_getn on fd ", portfd, " failed (errno=", e, ")\n")
throw("runtime: netpoll failed")
goto retry
var toRun gList
for i := 0; i < int(n); i++ {
ev := &events[i]
if ev.portev_events == 0 {
pd := (*pollDesc)(unsafe.Pointer(ev.portev_user))
var mode, clear int32
if (ev.portev_events & (_POLLIN | _POLLHUP | _POLLERR)) != 0 {
mode += 'r'
clear |= _POLLIN
if (ev.portev_events & (_POLLOUT | _POLLHUP | _POLLERR)) != 0 {
mode += 'w'
clear |= _POLLOUT
// To effect edge-triggered events, we need to be sure to
// update our association with whatever events were not
// set with the event. For example if we are registered
// for POLLIN|POLLOUT, and we get POLLIN, besides waking
// the goroutine interested in POLLIN we have to not forget
// about the one interested in POLLOUT.
if clear != 0 {
netpollupdate(pd, 0, uint32(clear))
if mode != 0 {
netpollready(&toRun, pd, mode)
if block && toRun.empty() {
goto retry
return toRun