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  //go:build darwin || dragonfly || freebsd || netbsd || openbsd
     6  // +build darwin dragonfly freebsd netbsd openbsd
     7  
     8  package runtime
     9  
    10  // Integrated network poller (kqueue-based implementation).
    11  
    12  import (
    13  	"runtime/internal/atomic"
    14  	"unsafe"
    15  )
    16  
    17  var (
    18  	kq int32 = -1
    19  
    20  	netpollBreakRd, netpollBreakWr uintptr // for netpollBreak
    21  
    22  	netpollWakeSig uint32 // used to avoid duplicate calls of netpollBreak
    23  )
    24  
    25  func netpollinit() {
    26  	kq = kqueue()
    27  	if kq < 0 {
    28  		println("runtime: kqueue failed with", -kq)
    29  		throw("runtime: netpollinit failed")
    30  	}
    31  	closeonexec(kq)
    32  	r, w, errno := nonblockingPipe()
    33  	if errno != 0 {
    34  		println("runtime: pipe failed with", -errno)
    35  		throw("runtime: pipe failed")
    36  	}
    37  	ev := keventt{
    38  		filter: _EVFILT_READ,
    39  		flags:  _EV_ADD,
    40  	}
    41  	*(*uintptr)(unsafe.Pointer(&ev.ident)) = uintptr(r)
    42  	n := kevent(kq, &ev, 1, nil, 0, nil)
    43  	if n < 0 {
    44  		println("runtime: kevent failed with", -n)
    45  		throw("runtime: kevent failed")
    46  	}
    47  	netpollBreakRd = uintptr(r)
    48  	netpollBreakWr = uintptr(w)
    49  }
    50  
    51  func netpollIsPollDescriptor(fd uintptr) bool {
    52  	return fd == uintptr(kq) || fd == netpollBreakRd || fd == netpollBreakWr
    53  }
    54  
    55  func netpollopen(fd uintptr, pd *pollDesc) int32 {
    56  	// Arm both EVFILT_READ and EVFILT_WRITE in edge-triggered mode (EV_CLEAR)
    57  	// for the whole fd lifetime. The notifications are automatically unregistered
    58  	// when fd is closed.
    59  	var ev [2]keventt
    60  	*(*uintptr)(unsafe.Pointer(&ev[0].ident)) = fd
    61  	ev[0].filter = _EVFILT_READ
    62  	ev[0].flags = _EV_ADD | _EV_CLEAR
    63  	ev[0].fflags = 0
    64  	ev[0].data = 0
    65  	ev[0].udata = (*byte)(unsafe.Pointer(pd))
    66  	ev[1] = ev[0]
    67  	ev[1].filter = _EVFILT_WRITE
    68  	n := kevent(kq, &ev[0], 2, nil, 0, nil)
    69  	if n < 0 {
    70  		return -n
    71  	}
    72  	return 0
    73  }
    74  
    75  func netpollclose(fd uintptr) int32 {
    76  	// Don't need to unregister because calling close()
    77  	// on fd will remove any kevents that reference the descriptor.
    78  	return 0
    79  }
    80  
    81  func netpollarm(pd *pollDesc, mode int) {
    82  	throw("runtime: unused")
    83  }
    84  
    85  // netpollBreak interrupts a kevent.
    86  func netpollBreak() {
    87  	if atomic.Cas(&netpollWakeSig, 0, 1) {
    88  		for {
    89  			var b byte
    90  			n := write(netpollBreakWr, unsafe.Pointer(&b), 1)
    91  			if n == 1 || n == -_EAGAIN {
    92  				break
    93  			}
    94  			if n == -_EINTR {
    95  				continue
    96  			}
    97  			println("runtime: netpollBreak write failed with", -n)
    98  			throw("runtime: netpollBreak write failed")
    99  		}
   100  	}
   101  }
   102  
   103  // netpoll checks for ready network connections.
   104  // Returns list of goroutines that become runnable.
   105  // delay < 0: blocks indefinitely
   106  // delay == 0: does not block, just polls
   107  // delay > 0: block for up to that many nanoseconds
   108  func netpoll(delay int64) gList {
   109  	if kq == -1 {
   110  		return gList{}
   111  	}
   112  	var tp *timespec
   113  	var ts timespec
   114  	if delay < 0 {
   115  		tp = nil
   116  	} else if delay == 0 {
   117  		tp = &ts
   118  	} else {
   119  		ts.setNsec(delay)
   120  		if ts.tv_sec > 1e6 {
   121  			// Darwin returns EINVAL if the sleep time is too long.
   122  			ts.tv_sec = 1e6
   123  		}
   124  		tp = &ts
   125  	}
   126  	var events [64]keventt
   127  retry:
   128  	n := kevent(kq, nil, 0, &events[0], int32(len(events)), tp)
   129  	if n < 0 {
   130  		if n != -_EINTR {
   131  			println("runtime: kevent on fd", kq, "failed with", -n)
   132  			throw("runtime: netpoll failed")
   133  		}
   134  		// If a timed sleep was interrupted, just return to
   135  		// recalculate how long we should sleep now.
   136  		if delay > 0 {
   137  			return gList{}
   138  		}
   139  		goto retry
   140  	}
   141  	var toRun gList
   142  	for i := 0; i < int(n); i++ {
   143  		ev := &events[i]
   144  
   145  		if uintptr(ev.ident) == netpollBreakRd {
   146  			if ev.filter != _EVFILT_READ {
   147  				println("runtime: netpoll: break fd ready for", ev.filter)
   148  				throw("runtime: netpoll: break fd ready for something unexpected")
   149  			}
   150  			if delay != 0 {
   151  				// netpollBreak could be picked up by a
   152  				// nonblocking poll. Only read the byte
   153  				// if blocking.
   154  				var tmp [16]byte
   155  				read(int32(netpollBreakRd), noescape(unsafe.Pointer(&tmp[0])), int32(len(tmp)))
   156  				atomic.Store(&netpollWakeSig, 0)
   157  			}
   158  			continue
   159  		}
   160  
   161  		var mode int32
   162  		switch ev.filter {
   163  		case _EVFILT_READ:
   164  			mode += 'r'
   165  
   166  			// On some systems when the read end of a pipe
   167  			// is closed the write end will not get a
   168  			// _EVFILT_WRITE event, but will get a
   169  			// _EVFILT_READ event with EV_EOF set.
   170  			// Note that setting 'w' here just means that we
   171  			// will wake up a goroutine waiting to write;
   172  			// that goroutine will try the write again,
   173  			// and the appropriate thing will happen based
   174  			// on what that write returns (success, EPIPE, EAGAIN).
   175  			if ev.flags&_EV_EOF != 0 {
   176  				mode += 'w'
   177  			}
   178  		case _EVFILT_WRITE:
   179  			mode += 'w'
   180  		}
   181  		if mode != 0 {
   182  			pd := (*pollDesc)(unsafe.Pointer(ev.udata))
   183  			pd.everr = false
   184  			if ev.flags == _EV_ERROR {
   185  				pd.everr = true
   186  			}
   187  			netpollready(&toRun, pd, mode)
   188  		}
   189  	}
   190  	return toRun
   191  }
   192
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