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Source file src/runtime/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  // +build linux
     7  
     8  package runtime
     9  
    10  import (
    11  	"runtime/internal/atomic"
    12  	"unsafe"
    13  )
    14  
    15  func epollcreate(size int32) int32
    16  func epollcreate1(flags int32) int32
    17  
    18  //go:noescape
    19  func epollctl(epfd, op, fd int32, ev *epollevent) int32
    20  
    21  //go:noescape
    22  func epollwait(epfd int32, ev *epollevent, nev, timeout int32) int32
    23  func closeonexec(fd int32)
    24  
    25  var (
    26  	epfd int32 = -1 // epoll descriptor
    27  
    28  	netpollBreakRd, netpollBreakWr uintptr // for netpollBreak
    29  
    30  	netpollWakeSig uint32 // used to avoid duplicate calls of netpollBreak
    31  )
    32  
    33  func netpollinit() {
    34  	epfd = epollcreate1(_EPOLL_CLOEXEC)
    35  	if epfd < 0 {
    36  		epfd = epollcreate(1024)
    37  		if epfd < 0 {
    38  			println("runtime: epollcreate failed with", -epfd)
    39  			throw("runtime: netpollinit failed")
    40  		}
    41  		closeonexec(epfd)
    42  	}
    43  	r, w, errno := nonblockingPipe()
    44  	if errno != 0 {
    45  		println("runtime: pipe failed with", -errno)
    46  		throw("runtime: pipe failed")
    47  	}
    48  	ev := epollevent{
    49  		events: _EPOLLIN,
    50  	}
    51  	*(**uintptr)(unsafe.Pointer(&ev.data)) = &netpollBreakRd
    52  	errno = epollctl(epfd, _EPOLL_CTL_ADD, r, &ev)
    53  	if errno != 0 {
    54  		println("runtime: epollctl failed with", -errno)
    55  		throw("runtime: epollctl failed")
    56  	}
    57  	netpollBreakRd = uintptr(r)
    58  	netpollBreakWr = uintptr(w)
    59  }
    60  
    61  func netpollIsPollDescriptor(fd uintptr) bool {
    62  	return fd == uintptr(epfd) || fd == netpollBreakRd || fd == netpollBreakWr
    63  }
    64  
    65  func netpollopen(fd uintptr, pd *pollDesc) int32 {
    66  	var ev epollevent
    67  	ev.events = _EPOLLIN | _EPOLLOUT | _EPOLLRDHUP | _EPOLLET
    68  	*(**pollDesc)(unsafe.Pointer(&ev.data)) = pd
    69  	return -epollctl(epfd, _EPOLL_CTL_ADD, int32(fd), &ev)
    70  }
    71  
    72  func netpollclose(fd uintptr) int32 {
    73  	var ev epollevent
    74  	return -epollctl(epfd, _EPOLL_CTL_DEL, int32(fd), &ev)
    75  }
    76  
    77  func netpollarm(pd *pollDesc, mode int) {
    78  	throw("runtime: unused")
    79  }
    80  
    81  // netpollBreak interrupts an epollwait.
    82  func netpollBreak() {
    83  	if atomic.Cas(&netpollWakeSig, 0, 1) {
    84  		for {
    85  			var b byte
    86  			n := write(netpollBreakWr, unsafe.Pointer(&b), 1)
    87  			if n == 1 {
    88  				break
    89  			}
    90  			if n == -_EINTR {
    91  				continue
    92  			}
    93  			if n == -_EAGAIN {
    94  				return
    95  			}
    96  			println("runtime: netpollBreak write failed with", -n)
    97  			throw("runtime: netpollBreak write failed")
    98  		}
    99  	}
   100  }
   101  
   102  // netpoll checks for ready network connections.
   103  // Returns list of goroutines that become runnable.
   104  // delay < 0: blocks indefinitely
   105  // delay == 0: does not block, just polls
   106  // delay > 0: block for up to that many nanoseconds
   107  func netpoll(delay int64) gList {
   108  	if epfd == -1 {
   109  		return gList{}
   110  	}
   111  	var waitms int32
   112  	if delay < 0 {
   113  		waitms = -1
   114  	} else if delay == 0 {
   115  		waitms = 0
   116  	} else if delay < 1e6 {
   117  		waitms = 1
   118  	} else if delay < 1e15 {
   119  		waitms = int32(delay / 1e6)
   120  	} else {
   121  		// An arbitrary cap on how long to wait for a timer.
   122  		// 1e9 ms == ~11.5 days.
   123  		waitms = 1e9
   124  	}
   125  	var events [128]epollevent
   126  retry:
   127  	n := epollwait(epfd, &events[0], int32(len(events)), waitms)
   128  	if n < 0 {
   129  		if n != -_EINTR {
   130  			println("runtime: epollwait on fd", epfd, "failed with", -n)
   131  			throw("runtime: netpoll failed")
   132  		}
   133  		// If a timed sleep was interrupted, just return to
   134  		// recalculate how long we should sleep now.
   135  		if waitms > 0 {
   136  			return gList{}
   137  		}
   138  		goto retry
   139  	}
   140  	var toRun gList
   141  	for i := int32(0); i < n; i++ {
   142  		ev := &events[i]
   143  		if ev.events == 0 {
   144  			continue
   145  		}
   146  
   147  		if *(**uintptr)(unsafe.Pointer(&ev.data)) == &netpollBreakRd {
   148  			if ev.events != _EPOLLIN {
   149  				println("runtime: netpoll: break fd ready for", ev.events)
   150  				throw("runtime: netpoll: break fd ready for something unexpected")
   151  			}
   152  			if delay != 0 {
   153  				// netpollBreak could be picked up by a
   154  				// nonblocking poll. Only read the byte
   155  				// if blocking.
   156  				var tmp [16]byte
   157  				read(int32(netpollBreakRd), noescape(unsafe.Pointer(&tmp[0])), int32(len(tmp)))
   158  				atomic.Store(&netpollWakeSig, 0)
   159  			}
   160  			continue
   161  		}
   162  
   163  		var mode int32
   164  		if ev.events&(_EPOLLIN|_EPOLLRDHUP|_EPOLLHUP|_EPOLLERR) != 0 {
   165  			mode += 'r'
   166  		}
   167  		if ev.events&(_EPOLLOUT|_EPOLLHUP|_EPOLLERR) != 0 {
   168  			mode += 'w'
   169  		}
   170  		if mode != 0 {
   171  			pd := *(**pollDesc)(unsafe.Pointer(&ev.data))
   172  			pd.everr = false
   173  			if ev.events == _EPOLLERR {
   174  				pd.everr = true
   175  			}
   176  			netpollready(&toRun, pd, mode)
   177  		}
   178  	}
   179  	return toRun
   180  }
   181  

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