netpoll_epoll.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 linux
     6  
     7  package runtime
     8  
     9  import (
    10  	"runtime/internal/atomic"
    11  	"unsafe"
    12  )
    13  
    14  func epollcreate(size int32) int32
    15  func epollcreate1(flags int32) int32
    16  
    17  //go:noescape
    18  func epollctl(epfd, op, fd int32, ev *epollevent) int32
    19  
    20  //go:noescape
    21  func epollwait(epfd int32, ev *epollevent, nev, timeout int32) int32
    22  func closeonexec(fd int32)
    23  
    24  var (
    25  	epfd int32 = -1 // epoll descriptor
    26  
    27  	netpollBreakRd, netpollBreakWr uintptr // for netpollBreak
    28  
    29  	netpollWakeSig uint32 // used to avoid duplicate calls of netpollBreak
    30  )
    31  
    32  func netpollinit() {
    33  	epfd = epollcreate1(_EPOLL_CLOEXEC)
    34  	if epfd < 0 {
    35  		epfd = epollcreate(1024)
    36  		if epfd < 0 {
    37  			println("runtime: epollcreate failed with", -epfd)
    38  			throw("runtime: netpollinit failed")
    39  		}
    40  		closeonexec(epfd)
    41  	}
    42  	r, w, errno := nonblockingPipe()
    43  	if errno != 0 {
    44  		println("runtime: pipe failed with", -errno)
    45  		throw("runtime: pipe failed")
    46  	}
    47  	ev := epollevent{
    48  		events: _EPOLLIN,
    49  	}
    50  	*(**uintptr)(unsafe.Pointer(&ev.data)) = &netpollBreakRd
    51  	errno = epollctl(epfd, _EPOLL_CTL_ADD, r, &ev)
    52  	if errno != 0 {
    53  		println("runtime: epollctl failed with", -errno)
    54  		throw("runtime: epollctl failed")
    55  	}
    56  	netpollBreakRd = uintptr(r)
    57  	netpollBreakWr = uintptr(w)
    58  }
    59  
    60  func netpollIsPollDescriptor(fd uintptr) bool {
    61  	return fd == uintptr(epfd) || fd == netpollBreakRd || fd == netpollBreakWr
    62  }
    63  
    64  func netpollopen(fd uintptr, pd *pollDesc) int32 {
    65  	var ev epollevent
    66  	ev.events = _EPOLLIN | _EPOLLOUT | _EPOLLRDHUP | _EPOLLET
    67  	*(**pollDesc)(unsafe.Pointer(&ev.data)) = pd
    68  	return -epollctl(epfd, _EPOLL_CTL_ADD, int32(fd), &ev)
    69  }
    70  
    71  func netpollclose(fd uintptr) int32 {
    72  	var ev epollevent
    73  	return -epollctl(epfd, _EPOLL_CTL_DEL, int32(fd), &ev)
    74  }
    75  
    76  func netpollarm(pd *pollDesc, mode int) {
    77  	throw("runtime: unused")
    78  }
    79  
    80  // netpollBreak interrupts an epollwait.
    81  func netpollBreak() {
    82  	if atomic.Cas(&netpollWakeSig, 0, 1) {
    83  		for {
    84  			var b byte
    85  			n := write(netpollBreakWr, unsafe.Pointer(&b), 1)
    86  			if n == 1 {
    87  				break
    88  			}
    89  			if n == -_EINTR {
    90  				continue
    91  			}
    92  			if n == -_EAGAIN {
    93  				return
    94  			}
    95  			println("runtime: netpollBreak write failed with", -n)
    96  			throw("runtime: netpollBreak write failed")
    97  		}
    98  	}
    99  }
   100  
   101  // netpoll checks for ready network connections.
   102  // Returns list of goroutines that become runnable.
   103  // delay < 0: blocks indefinitely
   104  // delay == 0: does not block, just polls
   105  // delay > 0: block for up to that many nanoseconds
   106  func netpoll(delay int64) gList {
   107  	if epfd == -1 {
   108  		return gList{}
   109  	}
   110  	var waitms int32
   111  	if delay < 0 {
   112  		waitms = -1
   113  	} else if delay == 0 {
   114  		waitms = 0
   115  	} else if delay < 1e6 {
   116  		waitms = 1
   117  	} else if delay < 1e15 {
   118  		waitms = int32(delay / 1e6)
   119  	} else {
   120  		// An arbitrary cap on how long to wait for a timer.
   121  		// 1e9 ms == ~11.5 days.
   122  		waitms = 1e9
   123  	}
   124  	var events [128]epollevent
   125  retry:
   126  	n := epollwait(epfd, &events[0], int32(len(events)), waitms)
   127  	if n < 0 {
   128  		if n != -_EINTR {
   129  			println("runtime: epollwait on fd", epfd, "failed with", -n)
   130  			throw("runtime: netpoll failed")
   131  		}
   132  		// If a timed sleep was interrupted, just return to
   133  		// recalculate how long we should sleep now.
   134  		if waitms > 0 {
   135  			return gList{}
   136  		}
   137  		goto retry
   138  	}
   139  	var toRun gList
   140  	for i := int32(0); i < n; i++ {
   141  		ev := &events[i]
   142  		if ev.events == 0 {
   143  			continue
   144  		}
   145  
   146  		if *(**uintptr)(unsafe.Pointer(&ev.data)) == &netpollBreakRd {
   147  			if ev.events != _EPOLLIN {
   148  				println("runtime: netpoll: break fd ready for", ev.events)
   149  				throw("runtime: netpoll: break fd ready for something unexpected")
   150  			}
   151  			if delay != 0 {
   152  				// netpollBreak could be picked up by a
   153  				// nonblocking poll. Only read the byte
   154  				// if blocking.
   155  				var tmp [16]byte
   156  				read(int32(netpollBreakRd), noescape(unsafe.Pointer(&tmp[0])), int32(len(tmp)))
   157  				atomic.Store(&netpollWakeSig, 0)
   158  			}
   159  			continue
   160  		}
   161  
   162  		var mode int32
   163  		if ev.events&(_EPOLLIN|_EPOLLRDHUP|_EPOLLHUP|_EPOLLERR) != 0 {
   164  			mode += 'r'
   165  		}
   166  		if ev.events&(_EPOLLOUT|_EPOLLHUP|_EPOLLERR) != 0 {
   167  			mode += 'w'
   168  		}
   169  		if mode != 0 {
   170  			pd := *(**pollDesc)(unsafe.Pointer(&ev.data))
   171  			pd.setEventErr(ev.events == _EPOLLERR)
   172  			netpollready(&toRun, pd, mode)
   173  		}
   174  	}
   175  	return toRun
   176  }
   177
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