// Which type of Process do we have?
	switch p.mode {
	case modeHandle:
		// pidfd
		return p.pidfdWait()
	case modePID:
		// Regular PID
		return p.pidWait()
	default:
		panic("unreachable")
	}
}

func (p *Process) pidWait() (*ProcessState, error) {
	// TODO(go.dev/issue/67642): When there are concurrent Wait calls, one
	// may wait on the wrong process if the PID is reused after the
	// completes its wait.

	// 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 {
	case statusDone:

	// rg, wg are accessed atomically and hold g pointers.
	// (Using atomic.Uintptr here is similar to using guintptr elsewhere.)
	rg atomic.Uintptr // pdReady, pdWait, G waiting for read or pdNil
	wg atomic.Uintptr // pdReady, pdWait, G waiting for write or pdNil

	lock    mutex // protects the following fields
	closing bool
	rrun    bool      // whether rt is running
	wrun    bool      // whether wt is running