libgo/go/os/wait_waitid.go

   1 // Copyright 2016 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 darwin linux
   6
   7 package os
   8
   9 import (
  10         "runtime"
  11         "syscall"
  12         "unsafe"
  13 )
  14
  15 const _P_PID = 1
  16
  17 // blockUntilWaitable attempts to block until a call to p.Wait will
  18 // succeed immediately, and returns whether it has done so.
  19 // It does not actually call p.Wait.
  20 func (p *Process) blockUntilWaitable() (bool, error) {
  21         // The waitid system call expects a pointer to a siginfo_t,
  22         // which is 128 bytes on all GNU/Linux systems.
  23         // On Darwin, it requires greater than or equal to 64 bytes
  24         // for darwin/{386,arm} and 104 bytes for darwin/amd64.
  25         // We don't care about the values it returns.
  26         var siginfo [16]uint64
  27         psig := &siginfo[0]
  28         _, _, e := syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
  29         runtime.KeepAlive(p)
  30         if e != 0 {
  31                 // waitid has been available since Linux 2.6.9, but
  32                 // reportedly is not available in Ubuntu on Windows.
  33                 // See issue 16610.
  34                 if e == syscall.ENOSYS {
  35                         return false, nil
  36                 }
  37                 return false, NewSyscallError("waitid", e)
  38         }
  39         return true, nil
  40 }