// aix, darwin, js/wasm, openbsd, solaris and wasip1/wasm don't implement
// waitid/wait6.

//go:build aix || darwin || (js && wasm) || openbsd || solaris || wasip1

package os

// 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.
// This version is used on systems that do not implement waitid,

//go:build dragonfly || freebsd || netbsd

package os

import (
	"runtime"
	"syscall"
)

// 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) {
	var errno syscall.Errno
	for {
		_, errno = wait6(_P_PID, p.Pid, syscall.WEXITED|syscall.WNOWAIT)

//go: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 Linux systems.

	//
	// Checking for statusDone here would not be a complete fix, as the PID
	// could still be waited on and reused prior to blockUntilWaitable.
	switch p.pidStatus() {
	case statusReleased:
		return nil, syscall.EINVAL
	}

	// If we can block until Wait4 will succeed immediately, do so.
	ready, err := p.blockUntilWaitable()
	if err != nil {
		return nil, err
	}
	if ready {
		// Mark the process done now, before the call to Wait4,

	// because the PID recycle issue doesn't exist (IOW, pidfd, unlike PID,
	// is guaranteed to refer to one particular process). Thus, there is no
	// need for the workaround (blockUntilWaitable + sigMu) from pidWait.
	//
	// We _do_ need to be careful about reuse of the pidfd FD number when
	// closing the pidfd. See handle for more details.
	handle, status := p.handleTransientAcquire()
	switch status {