// 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.
#include "runtime.h"
#include "arch_GOARCH.h"
#include "defs_GOOS_GOARCH.h"
#include "os_GOOS.h"
// 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/writting), 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
// asynchonously 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).
#pragma dynimport libc·fcntl fcntl "libc.so"
#pragma dynimport libc·port_create port_create "libc.so"
#pragma dynimport libc·port_associate port_associate "libc.so"
#pragma dynimport libc·port_dissociate port_dissociate "libc.so"
#pragma dynimport libc·port_getn port_getn "libc.so"
extern uintptr libc·fcntl;
extern uintptr libc·port_create;
extern uintptr libc·port_associate;
extern uintptr libc·port_dissociate;
extern uintptr libc·port_getn;
#define errno (*m->perrno)
int32
runtime·fcntl(int32 fd, int32 cmd, uintptr arg)
{
return runtime·sysvicall6(libc·fcntl, 3,
(uintptr)fd, (uintptr)cmd, (uintptr)arg);
}
int32
runtime·port_create(void)
{
return runtime·sysvicall6(libc·port_create, 0);
}
int32
runtime·port_associate(int32 port, int32 source, uintptr object, int32 events, uintptr user)
{
return runtime·sysvicall6(libc·port_associate,
5, (uintptr)port, (uintptr)source, object, (uintptr)events, user);
}
int32
runtime·port_dissociate(int32 port, int32 source, uintptr object)
{
return runtime·sysvicall6(libc·port_dissociate,
3, (uintptr)port, (uintptr)source, object);
}
int32
runtime·port_getn(int32 port, PortEvent *evs, uint32 max, uint32 *nget, Timespec *timeout)
{
return runtime·sysvicall6(libc·port_getn, 5, (uintptr)port,
(uintptr)evs, (uintptr)max, (uintptr)nget, (uintptr)timeout);
}
static int32 portfd = -1;
void
runtime·netpollinit(void)
{
if((portfd = runtime·port_create()) >= 0) {
runtime·fcntl(portfd, F_SETFD, FD_CLOEXEC);
return;
}
runtime·printf("netpollinit: failed to create port (%d)\n", errno);
runtime·throw("netpollinit: failed to create port");
}
int32
runtime·netpollopen(uintptr fd, PollDesc *pd)
{
int32 r;
runtime·netpolllock(pd);
// We don't register for any specific type of events yet, that's
// netpollarm's job. We merely ensure we call port_associate before
// asynchonous 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.
*runtime·netpolluser(pd) = 0;
r = runtime·port_associate(portfd, PORT_SOURCE_FD, fd, 0, (uintptr)pd);
runtime·netpollunlock(pd);
return r;
}
int32
runtime·netpollclose(uintptr fd)
{
return runtime·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.
void
runtime·netpollupdate(PollDesc* pd, uint32 set, uint32 clear)
{
uint32 *ep, old, events;
uintptr fd = runtime·netpollfd(pd);
ep = (uint32*)runtime·netpolluser(pd);
if(runtime·netpollclosing(pd))
return;
old = *ep;
events = (old & ~clear) | set;
if(old == events)
return;
if(events && runtime·port_associate(portfd, PORT_SOURCE_FD, fd, events, (uintptr)pd) != 0) {
runtime·printf("netpollupdate: failed to associate (%d)\n", errno);
runtime·throw("netpollupdate: failed to associate");
}
*ep = events;
}
// subscribe the fd to the port such that port_getn will return one event.
void
runtime·netpollarm(PollDesc* pd, int32 mode)
{
runtime·netpolllock(pd);
switch(mode) {
case 'r':
runtime·netpollupdate(pd, POLLIN, 0);
break;
case 'w':
runtime·netpollupdate(pd, POLLOUT, 0);
break;
default:
runtime·throw("netpollarm: bad mode");
}
runtime·netpollunlock(pd);
}
// polls for ready network connections
// returns list of goroutines that become runnable
G*
runtime·netpoll(bool block)
{
static int32 lasterr;
PortEvent events[128], *ev;
PollDesc *pd;
int32 i, mode, clear;
uint32 n;
Timespec *wait = nil, zero;
G *gp;
if(portfd == -1)
return (nil);
if(!block) {
zero.tv_sec = 0;
zero.tv_nsec = 0;
wait = &zero;
}
retry:
n = 1;
if(runtime·port_getn(portfd, events, nelem(events), &n, wait) < 0) {
if(errno != EINTR && errno != lasterr) {
lasterr = errno;
runtime·printf("runtime: port_getn on fd %d failed with %d\n", portfd, errno);
}
goto retry;
}
gp = nil;
for(i = 0; i < n; i++) {
ev = &events[i];
if(ev->portev_events == 0)
continue;
pd = (PollDesc *)ev->portev_user;
mode = 0;
clear = 0;
if(ev->portev_events & (POLLIN|POLLHUP|POLLERR)) {
mode += 'r';
clear |= POLLIN;
}
if(ev->portev_events & (POLLOUT|POLLHUP|POLLERR)) {
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) {
runtime·netpolllock(pd);
runtime·netpollupdate(pd, 0, clear);
runtime·netpollunlock(pd);
}
if(mode)
runtime·netpollready(&gp, pd, mode);
}
if(block && gp == nil)
goto retry;
return gp;
}