netpoll_aix.go

Documentation: runtime

     1  // Copyright 2018 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  package runtime
     6  
     7  import (
     8  	"runtime/internal/atomic"
     9  	"unsafe"
    10  )
    11  
    12  // This is based on the former libgo/runtime/netpoll_select.c implementation
    13  // except that it uses poll instead of select and is written in Go.
    14  // It's also based on Solaris implementation for the arming mechanisms
    15  
    16  //go:cgo_import_dynamic libc_poll poll "libc.a/shr_64.o"
    17  //go:linkname libc_poll libc_poll
    18  
    19  var libc_poll libFunc
    20  
    21  //go:nosplit
    22  func poll(pfds *pollfd, npfds uintptr, timeout uintptr) (int32, int32) {
    23  	r, err := syscall3(&libc_poll, uintptr(unsafe.Pointer(pfds)), npfds, timeout)
    24  	return int32(r), int32(err)
    25  }
    26  
    27  // pollfd represents the poll structure for AIX operating system.
    28  type pollfd struct {
    29  	fd      int32
    30  	events  int16
    31  	revents int16
    32  }
    33  
    34  const _POLLIN = 0x0001
    35  const _POLLOUT = 0x0002
    36  const _POLLHUP = 0x2000
    37  const _POLLERR = 0x4000
    38  
    39  var (
    40  	pfds           []pollfd
    41  	pds            []*pollDesc
    42  	mtxpoll        mutex
    43  	mtxset         mutex
    44  	rdwake         int32
    45  	wrwake         int32
    46  	pendingUpdates int32
    47  
    48  	netpollWakeSig uint32 // used to avoid duplicate calls of netpollBreak
    49  )
    50  
    51  func netpollinit() {
    52  	// Create the pipe we use to wakeup poll.
    53  	r, w, errno := nonblockingPipe()
    54  	if errno != 0 {
    55  		throw("netpollinit: failed to create pipe")
    56  	}
    57  	rdwake = r
    58  	wrwake = w
    59  
    60  	// Pre-allocate array of pollfd structures for poll.
    61  	pfds = make([]pollfd, 1, 128)
    62  
    63  	// Poll the read side of the pipe.
    64  	pfds[0].fd = rdwake
    65  	pfds[0].events = _POLLIN
    66  
    67  	pds = make([]*pollDesc, 1, 128)
    68  	pds[0] = nil
    69  }
    70  
    71  func netpollIsPollDescriptor(fd uintptr) bool {
    72  	return fd == uintptr(rdwake) || fd == uintptr(wrwake)
    73  }
    74  
    75  // netpollwakeup writes on wrwake to wakeup poll before any changes.
    76  func netpollwakeup() {
    77  	if pendingUpdates == 0 {
    78  		pendingUpdates = 1
    79  		b := [1]byte{0}
    80  		write(uintptr(wrwake), unsafe.Pointer(&b[0]), 1)
    81  	}
    82  }
    83  
    84  func netpollopen(fd uintptr, pd *pollDesc) int32 {
    85  	lock(&mtxpoll)
    86  	netpollwakeup()
    87  
    88  	lock(&mtxset)
    89  	unlock(&mtxpoll)
    90  
    91  	pd.user = uint32(len(pfds))
    92  	pfds = append(pfds, pollfd{fd: int32(fd)})
    93  	pds = append(pds, pd)
    94  	unlock(&mtxset)
    95  	return 0
    96  }
    97  
    98  func netpollclose(fd uintptr) int32 {
    99  	lock(&mtxpoll)
   100  	netpollwakeup()
   101  
   102  	lock(&mtxset)
   103  	unlock(&mtxpoll)
   104  
   105  	for i := 0; i < len(pfds); i++ {
   106  		if pfds[i].fd == int32(fd) {
   107  			pfds[i] = pfds[len(pfds)-1]
   108  			pfds = pfds[:len(pfds)-1]
   109  
   110  			pds[i] = pds[len(pds)-1]
   111  			pds[i].user = uint32(i)
   112  			pds = pds[:len(pds)-1]
   113  			break
   114  		}
   115  	}
   116  	unlock(&mtxset)
   117  	return 0
   118  }
   119  
   120  func netpollarm(pd *pollDesc, mode int) {
   121  	lock(&mtxpoll)
   122  	netpollwakeup()
   123  
   124  	lock(&mtxset)
   125  	unlock(&mtxpoll)
   126  
   127  	switch mode {
   128  	case 'r':
   129  		pfds[pd.user].events |= _POLLIN
   130  	case 'w':
   131  		pfds[pd.user].events |= _POLLOUT
   132  	}
   133  	unlock(&mtxset)
   134  }
   135  
   136  // netpollBreak interrupts a poll.
   137  func netpollBreak() {
   138  	if atomic.Cas(&netpollWakeSig, 0, 1) {
   139  		b := [1]byte{0}
   140  		write(uintptr(wrwake), unsafe.Pointer(&b[0]), 1)
   141  	}
   142  }
   143  
   144  // netpoll checks for ready network connections.
   145  // Returns list of goroutines that become runnable.
   146  // delay < 0: blocks indefinitely
   147  // delay == 0: does not block, just polls
   148  // delay > 0: block for up to that many nanoseconds
   149  //go:nowritebarrierrec
   150  func netpoll(delay int64) gList {
   151  	var timeout uintptr
   152  	if delay < 0 {
   153  		timeout = ^uintptr(0)
   154  	} else if delay == 0 {
   155  		// TODO: call poll with timeout == 0
   156  		return gList{}
   157  	} else if delay < 1e6 {
   158  		timeout = 1
   159  	} else if delay < 1e15 {
   160  		timeout = uintptr(delay / 1e6)
   161  	} else {
   162  		// An arbitrary cap on how long to wait for a timer.
   163  		// 1e9 ms == ~11.5 days.
   164  		timeout = 1e9
   165  	}
   166  retry:
   167  	lock(&mtxpoll)
   168  	lock(&mtxset)
   169  	pendingUpdates = 0
   170  	unlock(&mtxpoll)
   171  
   172  	n, e := poll(&pfds[0], uintptr(len(pfds)), timeout)
   173  	if n < 0 {
   174  		if e != _EINTR {
   175  			println("errno=", e, " len(pfds)=", len(pfds))
   176  			throw("poll failed")
   177  		}
   178  		unlock(&mtxset)
   179  		// If a timed sleep was interrupted, just return to
   180  		// recalculate how long we should sleep now.
   181  		if timeout > 0 {
   182  			return gList{}
   183  		}
   184  		goto retry
   185  	}
   186  	// Check if some descriptors need to be changed
   187  	if n != 0 && pfds[0].revents&(_POLLIN|_POLLHUP|_POLLERR) != 0 {
   188  		if delay != 0 {
   189  			// A netpollwakeup could be picked up by a
   190  			// non-blocking poll. Only clear the wakeup
   191  			// if blocking.
   192  			var b [1]byte
   193  			for read(rdwake, unsafe.Pointer(&b[0]), 1) == 1 {
   194  			}
   195  			atomic.Store(&netpollWakeSig, 0)
   196  		}
   197  		// Still look at the other fds even if the mode may have
   198  		// changed, as netpollBreak might have been called.
   199  		n--
   200  	}
   201  	var toRun gList
   202  	for i := 1; i < len(pfds) && n > 0; i++ {
   203  		pfd := &pfds[i]
   204  
   205  		var mode int32
   206  		if pfd.revents&(_POLLIN|_POLLHUP|_POLLERR) != 0 {
   207  			mode += 'r'
   208  			pfd.events &= ^_POLLIN
   209  		}
   210  		if pfd.revents&(_POLLOUT|_POLLHUP|_POLLERR) != 0 {
   211  			mode += 'w'
   212  			pfd.events &= ^_POLLOUT
   213  		}
   214  		if mode != 0 {
   215  			pds[i].everr = false
   216  			if pfd.revents == _POLLERR {
   217  				pds[i].everr = true
   218  			}
   219  			netpollready(&toRun, pds[i], mode)
   220  			n--
   221  		}
   222  	}
   223  	unlock(&mtxset)
   224  	return toRun
   225  }
   226
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