Bug Fix: SystemCPUfreq fails when any core is offline

sysfs/system_cpu.go

@@ -142,6 +142,49 @@ func parseCPUThermalThrottle(cpuPath string) (*CPUThermalThrottle, error) {
 	return &t, nil
 }
 
+func binSearch(elem uint16, elemSlice *[]uint16) bool {
+	if len(*elemSlice) == 0 {
+		return false
+	}
+
+	if len(*elemSlice) == 1 {
+		return elem == (*elemSlice)[0]
+	}
+
+	start := 0
+	end := len(*elemSlice) - 1
+
+	var mid int
+
+	for start <= end {
+		mid = (start + end) / 2
+		if (*elemSlice)[mid] == elem {
+			return true
+		} else if (*elemSlice)[mid] > elem {
+			end = mid - 1
+		} else if (*elemSlice)[mid] < elem {
+			start = mid + 1
+		}
+	}
+
+	return false
+}
+
+func filterOfflineCPUs(offlineCpus *[]uint16, cpus *[]string) error {
+	for i, cpu := range *cpus {
+		cpuName := strings.TrimPrefix(filepath.Base(cpu), "cpu")
+		cpuNameUint16, err := strconv.Atoi(cpuName)
+		if err != nil {
+			return err
+		}
+		if binSearch(uint16(cpuNameUint16), offlineCpus) {
+			*cpus = append((*cpus)[:i], (*cpus)[i+1:]...)
+		}
+	}
+
+	return nil
+}
+
 // SystemCpufreq returns CPU frequency metrics for all CPUs.
 func (fs FS) SystemCpufreq() ([]SystemCPUCpufreqStats, error) {
 	var g errgroup.Group
@@ -151,6 +194,25 @@ func (fs FS) SystemCpufreq() ([]SystemCPUCpufreqStats, error) {
 		return nil, err
 	}
 
+	line, err := util.ReadFileNoStat(fs.sys.Path("devices/system/cpu/offline"))
+	if err != nil {
+		return nil, err
+	}
+
+	if strings.TrimSpace(string(line)) != "" {
+		offlineCPUs, err := parseCPURange(line)
+		if err != nil {
+			return nil, err
+		}
+
+		if len(offlineCPUs) > 0 {
+			err = filterOfflineCPUs(&offlineCPUs, &cpus)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
 	systemCpufreq := make([]SystemCPUCpufreqStats, len(cpus))
 	for i, cpu := range cpus {
 		cpuName := strings.TrimPrefix(filepath.Base(cpu), "cpu")
@@ -251,12 +313,12 @@ func (fs FS) IsolatedCPUs() ([]uint16, error) {
 		return nil, err
 	}
 
-	return parseIsolatedCPUs(isolcpus)
+	return parseCPURange(isolcpus)
 }
 
-func parseIsolatedCPUs(data []byte) ([]uint16, error) {
+func parseCPURange(data []byte) ([]uint16, error) {
 
-	var isolcpusInt = []uint16{}
+	var cpusInt = []uint16{}
 
 	for _, cpu := range strings.Split(strings.TrimRight(string(data), "\n"), ",") {
 		if cpu == "" {
@@ -277,7 +339,7 @@ func parseIsolatedCPUs(data []byte) ([]uint16, error) {
 			}
 
 			for i := startRange; i <= endRange; i++ {
-				isolcpusInt = append(isolcpusInt, uint16(i))
+				cpusInt = append(cpusInt, uint16(i))
 			}
 			continue
 		}
@@ -286,7 +348,7 @@ func parseIsolatedCPUs(data []byte) ([]uint16, error) {
 		if err != nil {
 			return nil, err
 		}
-		isolcpusInt = append(isolcpusInt, uint16(cpuN))
+		cpusInt = append(cpusInt, uint16(cpuN))
 	}
-	return isolcpusInt, nil
+	return cpusInt, nil
 }

sysfs/system_cpu_test.go

@@ -165,7 +165,7 @@ func TestIsolatedParsingCPU(t *testing.T) {
 	}
 	for _, params := range testParams {
 		t.Run("blabla", func(t *testing.T) {
-			res, err := parseIsolatedCPUs(params.in)
+			res, err := parseCPURange(params.in)
 			if !reflect.DeepEqual(res, params.res) {
 				t.Fatalf("should have %v result: got %v", params.res, res)
 			}
@@ -193,3 +193,24 @@ func TestIsolatedCPUs(t *testing.T) {
 		t.Errorf("Error not correct: want %v, have %v", nil, err)
 	}
 }
+
+func TestBinSearch(t *testing.T) {
+	var testParams = []struct {
+		elem  uint16
+		elems []uint16
+		res   bool
+	}{
+		{3, []uint16{1, 3, 5, 7, 9}, true},
+		{4, []uint16{1, 3, 5, 7, 9}, false},
+		{2, []uint16{}, false},
+	}
+
+	for _, param := range testParams {
+		res := binSearch(param.elem, &param.elems)
+
+		if res != param.res {
+			t.Fatalf("Result not correct: want %v, have %v", param.res, res)
+		}
+
+	}
+}

testdata/fixtures.ttar

@@ -12721,6 +12721,11 @@ Lines: 1
 1,2-7,9
 Mode: 664
 # ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+Path: fixtures/sys/devices/system/cpu/offline
+Lines: 1
+2,12-15
+Mode: 664
+# ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Directory: fixtures/sys/devices/system/node
 Mode: 775
 # ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -