github.com/ltltlt/go-source-code@v0.0.0-20190830023027-95be009773aa/runtime/netpoll_epoll.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 linux
     6  
     7  package runtime
     8  
     9  import "unsafe"
    10  
    11  func epollcreate(size int32) int32
    12  func epollcreate1(flags int32) int32
    13  
    14  //go:noescape
    15  func epollctl(epfd, op, fd int32, ev *epollevent) int32
    16  
    17  //go:noescape
    18  func epollwait(epfd int32, ev *epollevent, nev, timeout int32) int32
    19  func closeonexec(fd int32)
    20  
    21  var (
    22  	epfd int32 = -1 // epoll descriptor
    23  )
    24  
    25  func netpollinit() {
    26  	epfd = epollcreate1(_EPOLL_CLOEXEC)
    27  	if epfd >= 0 {
    28  		return
    29  	}
    30  	epfd = epollcreate(1024)
    31  	if epfd >= 0 {
    32  		closeonexec(epfd)
    33  		return
    34  	}
    35  	println("runtime: epollcreate failed with", -epfd)
    36  	throw("runtime: netpollinit failed")
    37  }
    38  
    39  func netpolldescriptor() uintptr {
    40  	return uintptr(epfd)
    41  }
    42  
    43  // 注册一个fd, 让fd与这个pd关联
    44  func netpollopen(fd uintptr, pd *pollDesc) int32 {
    45  	var ev epollevent
    46  	ev.events = _EPOLLIN | _EPOLLOUT | _EPOLLRDHUP | _EPOLLET
    47  	*(**pollDesc)(unsafe.Pointer(&ev.data)) = pd
    48  	return -epollctl(epfd, _EPOLL_CTL_ADD, int32(fd), &ev)
    49  }
    50  
    51  func netpollclose(fd uintptr) int32 {
    52  	var ev epollevent
    53  	return -epollctl(epfd, _EPOLL_CTL_DEL, int32(fd), &ev)
    54  }
    55  
    56  func netpollarm(pd *pollDesc, mode int) {
    57  	throw("runtime: unused")
    58  }
    59  
    60  // polls for ready network connections
    61  // 轮询准备好的网络连接
    62  // returns list of goroutines that become runnable
    63  // 返回可运行的goroutine列表
    64  func netpoll(block bool) *g {
    65  	if epfd == -1 {
    66  		return nil
    67  	}
    68  	waitms := int32(-1)
    69  	if !block {
    70  		waitms = 0
    71  	}
    72  	var events [128]epollevent
    73  retry:
    74  	n := epollwait(epfd, &events[0], int32(len(events)), waitms)
    75  	if n < 0 {
    76  		if n != -_EINTR {
    77  			println("runtime: epollwait on fd", epfd, "failed with", -n)
    78  			throw("runtime: netpoll failed")
    79  		}
    80  		goto retry
    81  	}
    82  	var gp guintptr
    83  	// 把结果串成一个链表, 先遍历到的放后面
    84  	for i := int32(0); i < n; i++ {
    85  		ev := &events[i]
    86  		if ev.events == 0 {
    87  			continue
    88  		}
    89  		var mode int32
    90  		if ev.events&(_EPOLLIN|_EPOLLRDHUP|_EPOLLHUP|_EPOLLERR) != 0 {
    91  			mode += 'r'
    92  		}
    93  		if ev.events&(_EPOLLOUT|_EPOLLHUP|_EPOLLERR) != 0 {
    94  			mode += 'w'
    95  		}
    96  		if mode != 0 {
    97  			pd := *(**pollDesc)(unsafe.Pointer(&ev.data))
    98  
    99  			netpollready(&gp, pd, mode)
   100  		}
   101  	}
   102  	if block && gp == 0 {
   103  		goto retry
   104  	}
   105  	return gp.ptr()
   106  }