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Source file src/runtime/netpoll_kqueue.go

Documentation: runtime

     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  func kqueue() int32
    14  
    15  //go:noescape
    16  func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timespec) int32
    17  func closeonexec(fd int32)
    18  
    19  var (
    20  	kq int32 = -1
    21  )
    22  
    23  func netpollinit() {
    24  	kq = kqueue()
    25  	if kq < 0 {
    26  		println("runtime: kqueue failed with", -kq)
    27  		throw("runtime: netpollinit failed")
    28  	}
    29  	closeonexec(kq)
    30  }
    31  
    32  func netpolldescriptor() uintptr {
    33  	return uintptr(kq)
    34  }
    35  
    36  func netpollopen(fd uintptr, pd *pollDesc) int32 {
    37  	// Arm both EVFILT_READ and EVFILT_WRITE in edge-triggered mode (EV_CLEAR)
    38  	// for the whole fd lifetime. The notifications are automatically unregistered
    39  	// when fd is closed.
    40  	var ev [2]keventt
    41  	*(*uintptr)(unsafe.Pointer(&ev[0].ident)) = fd
    42  	ev[0].filter = _EVFILT_READ
    43  	ev[0].flags = _EV_ADD | _EV_CLEAR
    44  	ev[0].fflags = 0
    45  	ev[0].data = 0
    46  	ev[0].udata = (*byte)(unsafe.Pointer(pd))
    47  	ev[1] = ev[0]
    48  	ev[1].filter = _EVFILT_WRITE
    49  	n := kevent(kq, &ev[0], 2, nil, 0, nil)
    50  	if n < 0 {
    51  		return -n
    52  	}
    53  	return 0
    54  }
    55  
    56  func netpollclose(fd uintptr) int32 {
    57  	// Don't need to unregister because calling close()
    58  	// on fd will remove any kevents that reference the descriptor.
    59  	return 0
    60  }
    61  
    62  func netpollarm(pd *pollDesc, mode int) {
    63  	throw("runtime: unused")
    64  }
    65  
    66  // Polls for ready network connections.
    67  // Returns list of goroutines that become runnable.
    68  func netpoll(block bool) *g {
    69  	if kq == -1 {
    70  		return nil
    71  	}
    72  	var tp *timespec
    73  	var ts timespec
    74  	if !block {
    75  		tp = &ts
    76  	}
    77  	var events [64]keventt
    78  retry:
    79  	n := kevent(kq, nil, 0, &events[0], int32(len(events)), tp)
    80  	if n < 0 {
    81  		if n != -_EINTR {
    82  			println("runtime: kevent on fd", kq, "failed with", -n)
    83  			throw("runtime: netpoll failed")
    84  		}
    85  		goto retry
    86  	}
    87  	var gp guintptr
    88  	for i := 0; i < int(n); i++ {
    89  		ev := &events[i]
    90  		var mode int32
    91  		switch ev.filter {
    92  		case _EVFILT_READ:
    93  			mode += 'r'
    94  
    95  			// On some systems when the read end of a pipe
    96  			// is closed the write end will not get a
    97  			// _EVFILT_WRITE event, but will get a
    98  			// _EVFILT_READ event with EV_EOF set.
    99  			// Note that setting 'w' here just means that we
   100  			// will wake up a goroutine waiting to write;
   101  			// that goroutine will try the write again,
   102  			// and the appropriate thing will happen based
   103  			// on what that write returns (success, EPIPE, EAGAIN).
   104  			if ev.flags&_EV_EOF != 0 {
   105  				mode += 'w'
   106  			}
   107  		case _EVFILT_WRITE:
   108  			mode += 'w'
   109  		}
   110  		if mode != 0 {
   111  			netpollready(&gp, (*pollDesc)(unsafe.Pointer(ev.udata)), mode)
   112  		}
   113  	}
   114  	if block && gp == 0 {
   115  		goto retry
   116  	}
   117  	return gp.ptr()
   118  }
   119  

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