preemptall()
	// stop current P
	gp.m.p.ptr().status = _Pgcstop // Pgcstop is only diagnostic.
	gp.m.p.ptr().gcStopTime = start
	sched.stopwait--
	// try to retake all P's in Psyscall status
	trace = traceAcquire()
	for _, pp := range allp {
		s := pp.status
		if s == _Psyscall && atomic.Cas(&pp.status, s, _Pgcstop) {
			if trace.ok() {
				trace.ProcSteal(pp, false)
			}