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 //go: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 reports 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 Linux systems.
  26         // On darwin/amd64, it requires 104 bytes.
  27         // We don't care about the values it returns.
  28         var siginfo [16]uint64
  29         psig := &siginfo[0]
  30         var r uintptr
  31         var e syscall.Errno
  32         for {
  33                 r, _, e = syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
  34                 if e != syscall.EINTR {
  35                         break
  36                 }
  37         }
  38         runtime.KeepAlive(p)
  39         // Check r as well as e because syscall.Syscall6 currently
  40         // just returns errno, and the SIGCHLD signal handler may
  41         // change errno. See https://gcc.gnu.org/PR86331.
  42         if r != 0 && e != 0 {
  43                 // waitid has been available since Linux 2.6.9, but
  44                 // reportedly is not available in Ubuntu on Windows.
  45                 // See issue 16610.
  46                 if e == syscall.ENOSYS {
  47                         return false, nil
  48                 }
  49                 return false, NewSyscallError("waitid", e)
  50         }
  51         return true, nil
  52 }