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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"
)
// 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 "libc.so"
//go:cgo_import_dynamic libc_port_associate port_associate "libc.so"
//go:cgo_import_dynamic libc_port_dissociate port_dissociate "libc.so"
//go:cgo_import_dynamic libc_port_getn port_getn "libc.so"
//go:cgo_import_dynamic libc_port_alert port_alert "libc.so"
//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
//go:linkname libc_port_alert libc_port_alert
var (
libc_port_create,
libc_port_associate,
libc_port_dissociate,
libc_port_getn,
libc_port_alert libcFunc
netpollWakeSig atomic.Uint32 // used to avoid duplicate calls of netpollBreak
)
func errno() int32 {
return *getg().m.perrno
}
func fcntl(fd, cmd, arg int32) int32 {
return int32(sysvicall3(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(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))))
}
func port_alert(port int32, flags, events uint32, user uintptr) int32 {
return int32(sysvicall4(&libc_port_alert, uintptr(port), uintptr(flags), uintptr(events), user))
}
var portfd int32 = -1
func netpollinit() {
portfd = port_create()
if portfd >= 0 {
fcntl(portfd, _F_SETFD, _FD_CLOEXEC)
return
}
print("runtime: port_create failed (errno=", errno(), ")\n")
throw("runtime: netpollinit failed")
}
func netpollIsPollDescriptor(fd uintptr) bool {
return fd == uintptr(portfd)
}
func netpollopen(fd uintptr, pd *pollDesc) int32 {
lock(&pd.lock)
// 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)))
unlock(&pd.lock)
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.info().closing() {
return
}
old := pd.user
events := (old & ^clear) | set
if old == events {
return
}
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) {
lock(&pd.lock)
switch mode {
case 'r':
netpollupdate(pd, _POLLIN, 0)
case 'w':
netpollupdate(pd, _POLLOUT, 0)
default:
throw("runtime: bad mode")
}
unlock(&pd.lock)
}
// netpollBreak interrupts a port_getn wait.
func netpollBreak() {
// Failing to cas indicates there is an in-flight wakeup, so we're done here.
if !netpollWakeSig.CompareAndSwap(0, 1) {
return
}
// Use port_alert to put portfd into alert mode.
// This will wake up all threads sleeping in port_getn on portfd,
// and cause their calls to port_getn to return immediately.
// Further, until portfd is taken out of alert mode,
// all calls to port_getn will return immediately.
if port_alert(portfd, _PORT_ALERT_UPDATE, _POLLHUP, uintptr(unsafe.Pointer(&portfd))) < 0 {
if e := errno(); e != _EBUSY {
println("runtime: port_alert failed with", e)
throw("runtime: netpoll: port_alert failed")
}
}
}
// netpoll checks for ready network connections.
// Returns list of goroutines that become runnable.
// delay < 0: blocks indefinitely
// delay == 0: does not block, just polls
// delay > 0: block for up to that many nanoseconds
func netpoll(delay int64) gList {
if portfd == -1 {
return gList{}
}
var wait *timespec
var ts timespec
if delay < 0 {
wait = nil
} else if delay == 0 {
wait = &ts
} else {
ts.setNsec(delay)
if ts.tv_sec > 1e6 {
// An arbitrary cap on how long to wait for a timer.
// 1e6 s == ~11.5 days.
ts.tv_sec = 1e6
}
wait = &ts
}
var events [128]portevent
retry:
var n uint32 = 1
r := port_getn(portfd, &events[0], uint32(len(events)), &n, wait)
e := errno()
if r < 0 && e == _ETIME && n > 0 {
// As per port_getn(3C), an ETIME failure does not preclude the
// delivery of some number of events. Treat a timeout failure
// with delivered events as a success.
r = 0
}
if r < 0 {
if e != _EINTR && e != _ETIME {
print("runtime: port_getn on fd ", portfd, " failed (errno=", e, ")\n")
throw("runtime: netpoll failed")
}
// If a timed sleep was interrupted and there are no events,
// just return to recalculate how long we should sleep now.
if delay > 0 {
return gList{}
}
goto retry
}
var toRun gList
for i := 0; i < int(n); i++ {
ev := &events[i]
if ev.portev_source == _PORT_SOURCE_ALERT {
if ev.portev_events != _POLLHUP || unsafe.Pointer(ev.portev_user) != unsafe.Pointer(&portfd) {
throw("runtime: netpoll: bad port_alert wakeup")
}
if delay != 0 {
// Now that a blocking call to netpoll
// has seen the alert, take portfd
// back out of alert mode.
// See the comment in netpollBreak.
if port_alert(portfd, 0, 0, 0) < 0 {
e := errno()
println("runtime: port_alert failed with", e)
throw("runtime: netpoll: port_alert failed")
}
netpollWakeSig.Store(0)
}
continue
}
if ev.portev_events == 0 {
continue
}
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 {
lock(&pd.lock)
netpollupdate(pd, 0, uint32(clear))
unlock(&pd.lock)
}
if mode != 0 {
// TODO(mikio): Consider implementing event
// scanning error reporting once we are sure
// about the event port on SmartOS.
//
// See golang.org/x/issue/30840.
netpollready(&toRun, pd, mode)
}
}
return toRun
}