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 // We used to used this code for Darwin, but according to issue #19314
   6 // waitid returns if the process is stopped, even when using WEXITED.
   7
   8 // +build linux
   9
  10 package os
  11
  12 import (
  13         "runtime"
  14         "syscall"
  15         "unsafe"
  16 )
  17
  18 const _P_PID = 1
  19
  20 // blockUntilWaitable attempts to block until a call to p.Wait will
  21 // succeed immediately, and returns whether it has done so.
  22 // It does not actually call p.Wait.
  23 func (p *Process) blockUntilWaitable() (bool, error) {
  24         // The waitid system call expects a pointer to a siginfo_t,
  25         // which is 128 bytes on all GNU/Linux systems.
  26         // On Darwin, it requires greater than or equal to 64 bytes
  27         // for darwin/{386,arm} and 104 bytes for darwin/amd64.
  28         // We don't care about the values it returns.
  29         var siginfo [16]uint64
  30         psig := &siginfo[0]
  31         r, _, e := syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
  32         runtime.KeepAlive(p)
  33         // Check r as well as e because syscall.Syscall6 currently
  34         // just returns errno, and the SIGCHLD signal handler may
  35         // change errno. See https://gcc.gnu.org/PR86331.
  36         if r != 0 && e != 0 {
  37                 // waitid has been available since Linux 2.6.9, but
  38                 // reportedly is not available in Ubuntu on Windows.
  39                 // See issue 16610.
  40                 if e == syscall.ENOSYS {
  41                         return false, nil
  42                 }
  43                 return false, NewSyscallError("waitid", e)
  44         }
  45         return true, nil
  46 }