summaryrefslogtreecommitdiffstats
path: root/src/runtime/netpoll_windows.go
blob: bb77d8d045efc51fb2ee61227383b4a1c8ec5b67 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
// Copyright 2013 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"
)

const _DWORD_MAX = 0xffffffff

const _INVALID_HANDLE_VALUE = ^uintptr(0)

// net_op must be the same as beginning of internal/poll.operation.
// Keep these in sync.
type net_op struct {
	// used by windows
	o overlapped
	// used by netpoll
	pd    *pollDesc
	mode  int32
	errno int32
	qty   uint32
}

type overlappedEntry struct {
	key      *pollDesc
	op       *net_op // In reality it's *overlapped, but we cast it to *net_op anyway.
	internal uintptr
	qty      uint32
}

var (
	iocphandle uintptr = _INVALID_HANDLE_VALUE // completion port io handle

	netpollWakeSig atomic.Uint32 // used to avoid duplicate calls of netpollBreak
)

func netpollinit() {
	iocphandle = stdcall4(_CreateIoCompletionPort, _INVALID_HANDLE_VALUE, 0, 0, _DWORD_MAX)
	if iocphandle == 0 {
		println("runtime: CreateIoCompletionPort failed (errno=", getlasterror(), ")")
		throw("runtime: netpollinit failed")
	}
}

func netpollIsPollDescriptor(fd uintptr) bool {
	return fd == iocphandle
}

func netpollopen(fd uintptr, pd *pollDesc) int32 {
	// TODO(iant): Consider using taggedPointer on 64-bit systems.
	if stdcall4(_CreateIoCompletionPort, fd, iocphandle, uintptr(unsafe.Pointer(pd)), 0) == 0 {
		return int32(getlasterror())
	}
	return 0
}

func netpollclose(fd uintptr) int32 {
	// nothing to do
	return 0
}

func netpollarm(pd *pollDesc, mode int) {
	throw("runtime: unused")
}

func netpollBreak() {
	// Failing to cas indicates there is an in-flight wakeup, so we're done here.
	if !netpollWakeSig.CompareAndSwap(0, 1) {
		return
	}

	if stdcall4(_PostQueuedCompletionStatus, iocphandle, 0, 0, 0) == 0 {
		println("runtime: netpoll: PostQueuedCompletionStatus failed (errno=", getlasterror(), ")")
		throw("runtime: netpoll: PostQueuedCompletionStatus 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 {
	var entries [64]overlappedEntry
	var wait, qty, flags, n, i uint32
	var errno int32
	var op *net_op
	var toRun gList

	mp := getg().m

	if iocphandle == _INVALID_HANDLE_VALUE {
		return gList{}
	}
	if delay < 0 {
		wait = _INFINITE
	} else if delay == 0 {
		wait = 0
	} else if delay < 1e6 {
		wait = 1
	} else if delay < 1e15 {
		wait = uint32(delay / 1e6)
	} else {
		// An arbitrary cap on how long to wait for a timer.
		// 1e9 ms == ~11.5 days.
		wait = 1e9
	}

	n = uint32(len(entries) / int(gomaxprocs))
	if n < 8 {
		n = 8
	}
	if delay != 0 {
		mp.blocked = true
	}
	if stdcall6(_GetQueuedCompletionStatusEx, iocphandle, uintptr(unsafe.Pointer(&entries[0])), uintptr(n), uintptr(unsafe.Pointer(&n)), uintptr(wait), 0) == 0 {
		mp.blocked = false
		errno = int32(getlasterror())
		if errno == _WAIT_TIMEOUT {
			return gList{}
		}
		println("runtime: GetQueuedCompletionStatusEx failed (errno=", errno, ")")
		throw("runtime: netpoll failed")
	}
	mp.blocked = false
	for i = 0; i < n; i++ {
		op = entries[i].op
		if op != nil && op.pd == entries[i].key {
			errno = 0
			qty = 0
			if stdcall5(_WSAGetOverlappedResult, op.pd.fd, uintptr(unsafe.Pointer(op)), uintptr(unsafe.Pointer(&qty)), 0, uintptr(unsafe.Pointer(&flags))) == 0 {
				errno = int32(getlasterror())
			}
			handlecompletion(&toRun, op, errno, qty)
		} else {
			netpollWakeSig.Store(0)
			if delay == 0 {
				// Forward the notification to the
				// blocked poller.
				netpollBreak()
			}
		}
	}
	return toRun
}

func handlecompletion(toRun *gList, op *net_op, errno int32, qty uint32) {
	mode := op.mode
	if mode != 'r' && mode != 'w' {
		println("runtime: GetQueuedCompletionStatusEx returned invalid mode=", mode)
		throw("runtime: netpoll failed")
	}
	op.errno = errno
	op.qty = qty
	netpollready(toRun, op.pd, mode)
}