if cpuprof.on || cpuprof.log != nil {
			print("runtime: cannot set cpu profile rate until previous profile has finished.\n")
			unlock(&cpuprof.lock)
			return
		}

		cpuprof.on = true
		cpuprof.log = newProfBuf(1, profBufWordCount, profBufTagCount)
		hdr := [1]uint64{uint64(hz)}
		cpuprof.log.write(nil, nanotime(), hdr[:], nil)
		setcpuprofilerate(int32(hz))
	} else if cpuprof.on {
		setcpuprofilerate(0)
		cpuprof.on = false