Change to using gopsutil for cross-OS process ops

Instead of trying to write out own code to do basic process
operations (e.g. checking if a PID is still running in a multi-OS
friendly manner), use shirou/gopsutil, a multi-platform library
that should abstract all the complexity away. Unlike our previous
approach on Windows, this one should actually work.

Signed-off-by: Matt Heon <mheon@redhat.com>

vendor/github.com/tklauser/numcpus/numcpus_linux.go

@@ -0,0 +1,120 @@
+// Copyright 2018 Tobias Klauser
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package numcpus
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+const sysfsCPUBasePath = "/sys/devices/system/cpu"
+
+func getFromCPUAffinity() (int, error) {
+	var cpuSet unix.CPUSet
+	if err := unix.SchedGetaffinity(0, &cpuSet); err != nil {
+		return 0, err
+	}
+	return cpuSet.Count(), nil
+}
+
+func readCPURange(file string) (int, error) {
+	buf, err := ioutil.ReadFile(filepath.Join(sysfsCPUBasePath, file))
+	if err != nil {
+		return 0, err
+	}
+	return parseCPURange(strings.Trim(string(buf), "\n "))
+}
+
+func parseCPURange(cpus string) (int, error) {
+	n := int(0)
+	for _, cpuRange := range strings.Split(cpus, ",") {
+		if len(cpuRange) == 0 {
+			continue
+		}
+		rangeOp := strings.SplitN(cpuRange, "-", 2)
+		first, err := strconv.ParseUint(rangeOp[0], 10, 32)
+		if err != nil {
+			return 0, err
+		}
+		if len(rangeOp) == 1 {
+			n++
+			continue
+		}
+		last, err := strconv.ParseUint(rangeOp[1], 10, 32)
+		if err != nil {
+			return 0, err
+		}
+		n += int(last - first + 1)
+	}
+	return n, nil
+}
+
+func getConfigured() (int, error) {
+	d, err := os.Open(sysfsCPUBasePath)
+	if err != nil {
+		return 0, err
+	}
+	defer d.Close()
+	fis, err := d.Readdir(-1)
+	if err != nil {
+		return 0, err
+	}
+	count := 0
+	for _, fi := range fis {
+		if name := fi.Name(); fi.IsDir() && strings.HasPrefix(name, "cpu") {
+			_, err := strconv.ParseInt(name[3:], 10, 64)
+			if err == nil {
+				count++
+			}
+		}
+	}
+	return count, nil
+}
+
+func getKernelMax() (int, error) {
+	buf, err := ioutil.ReadFile(filepath.Join(sysfsCPUBasePath, "kernel_max"))
+	if err != nil {
+		return 0, err
+	}
+	n, err := strconv.ParseInt(strings.Trim(string(buf), "\n "), 10, 32)
+	if err != nil {
+		return 0, err
+	}
+	return int(n), nil
+}
+
+func getOffline() (int, error) {
+	return readCPURange("offline")
+}
+
+func getOnline() (int, error) {
+	if n, err := getFromCPUAffinity(); err == nil {
+		return n, nil
+	}
+	return readCPURange("online")
+}
+
+func getPossible() (int, error) {
+	return readCPURange("possible")
+}
+
+func getPresent() (int, error) {
+	return readCPURange("present")
+}