github.com/hikaru7719/go@v0.0.0-20181025140707-c8b2ac68906a/src/runtime/netpoll_kqueue.go (about)

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // +build darwin dragonfly freebsd netbsd openbsd
     6  
     7  package runtime
     8  
     9  // Integrated network poller (kqueue-based implementation).
    10  
    11  import "unsafe"
    12  
    13  var (
    14  	kq int32 = -1
    15  )
    16  
    17  func netpollinit() {
    18  	kq = kqueue()
    19  	if kq < 0 {
    20  		println("runtime: kqueue failed with", -kq)
    21  		throw("runtime: netpollinit failed")
    22  	}
    23  	closeonexec(kq)
    24  }
    25  
    26  func netpolldescriptor() uintptr {
    27  	return uintptr(kq)
    28  }
    29  
    30  func netpollopen(fd uintptr, pd *pollDesc) int32 {
    31  	// Arm both EVFILT_READ and EVFILT_WRITE in edge-triggered mode (EV_CLEAR)
    32  	// for the whole fd lifetime. The notifications are automatically unregistered
    33  	// when fd is closed.
    34  	var ev [2]keventt
    35  	*(*uintptr)(unsafe.Pointer(&ev[0].ident)) = fd
    36  	ev[0].filter = _EVFILT_READ
    37  	ev[0].flags = _EV_ADD | _EV_CLEAR
    38  	ev[0].fflags = 0
    39  	ev[0].data = 0
    40  	ev[0].udata = (*byte)(unsafe.Pointer(pd))
    41  	ev[1] = ev[0]
    42  	ev[1].filter = _EVFILT_WRITE
    43  	n := kevent(kq, &ev[0], 2, nil, 0, nil)
    44  	if n < 0 {
    45  		return -n
    46  	}
    47  	return 0
    48  }
    49  
    50  func netpollclose(fd uintptr) int32 {
    51  	// Don't need to unregister because calling close()
    52  	// on fd will remove any kevents that reference the descriptor.
    53  	return 0
    54  }
    55  
    56  func netpollarm(pd *pollDesc, mode int) {
    57  	throw("runtime: unused")
    58  }
    59  
    60  // Polls for ready network connections.
    61  // Returns list of goroutines that become runnable.
    62  func netpoll(block bool) gList {
    63  	if kq == -1 {
    64  		return gList{}
    65  	}
    66  	var tp *timespec
    67  	var ts timespec
    68  	if !block {
    69  		tp = &ts
    70  	}
    71  	var events [64]keventt
    72  retry:
    73  	n := kevent(kq, nil, 0, &events[0], int32(len(events)), tp)
    74  	if n < 0 {
    75  		if n != -_EINTR {
    76  			println("runtime: kevent on fd", kq, "failed with", -n)
    77  			throw("runtime: netpoll failed")
    78  		}
    79  		goto retry
    80  	}
    81  	var toRun gList
    82  	for i := 0; i < int(n); i++ {
    83  		ev := &events[i]
    84  		var mode int32
    85  		switch ev.filter {
    86  		case _EVFILT_READ:
    87  			mode += 'r'
    88  
    89  			// On some systems when the read end of a pipe
    90  			// is closed the write end will not get a
    91  			// _EVFILT_WRITE event, but will get a
    92  			// _EVFILT_READ event with EV_EOF set.
    93  			// Note that setting 'w' here just means that we
    94  			// will wake up a goroutine waiting to write;
    95  			// that goroutine will try the write again,
    96  			// and the appropriate thing will happen based
    97  			// on what that write returns (success, EPIPE, EAGAIN).
    98  			if ev.flags&_EV_EOF != 0 {
    99  				mode += 'w'
   100  			}
   101  		case _EVFILT_WRITE:
   102  			mode += 'w'
   103  		}
   104  		if mode != 0 {
   105  			netpollready(&toRun, (*pollDesc)(unsafe.Pointer(ev.udata)), mode)
   106  		}
   107  	}
   108  	if block && toRun.empty() {
   109  		goto retry
   110  	}
   111  	return toRun
   112  }