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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// We used to used this code for Darwin, but according to issue #19314
// waitid returns if the process is stopped, even when using WEXITED.
// +build linux
package os
import (
"runtime"
"syscall"
"unsafe"
)
const _P_PID = 1
// blockUntilWaitable attempts to block until a call to p.Wait will
// succeed immediately, and reports whether it has done so.
// It does not actually call p.Wait.
func (p *Process) blockUntilWaitable() (bool, error) {
// The waitid system call expects a pointer to a siginfo_t,
// which is 128 bytes on all GNU/Linux systems.
// On Darwin, it requires greater than or equal to 64 bytes
// for darwin/{386,arm} and 104 bytes for darwin/amd64.
// We don't care about the values it returns.
var siginfo [16]uint64
psig := &siginfo[0]
r, _, e := syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
runtime.KeepAlive(p)
// Check r as well as e because syscall.Syscall6 currently
// just returns errno, and the SIGCHLD signal handler may
// change errno. See https://gcc.gnu.org/PR86331.
if r != 0 && e != 0 {
// waitid has been available since Linux 2.6.9, but
// reportedly is not available in Ubuntu on Windows.
// See issue 16610.
if e == syscall.ENOSYS {
return false, nil
}
return false, NewSyscallError("waitid", e)
}
return true, nil
}
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