From 6c4d375cd30489c3a14ae4ddd1970bacd457b293 Mon Sep 17 00:00:00 2001
From: SuperQ <superq@gmail.com>
Date: Sun, 8 Mar 2026 11:39:08 +0100
Subject: [PATCH] Refactor class thermal error handling

Include any read errors when parsing /sys/class/thermal/thermal_zone
data. This avoids premature error returns if there are platform specific
problems like `temp` being unreadable, even tho it's a required file.

Related to: https://github.com/prometheus/node_exporter/issues/2980

Signed-off-by: SuperQ <superq@gmail.com>
---
 sysfs/class_thermal.go      | 44 +++++++++++++++++--------------------
 sysfs/class_thermal_test.go | 26 ++++++++++++----------
 2 files changed, 34 insertions(+), 36 deletions(-)

diff --git a/sysfs/class_thermal.go b/sysfs/class_thermal.go
index db832867..8372f137 100644
--- a/sysfs/class_thermal.go
+++ b/sysfs/class_thermal.go
@@ -17,12 +17,10 @@ package sysfs
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
-	"syscall"
-
-	fsp "io/fs"
 
 	"github.com/prometheus/procfs/internal/util"
 )
@@ -37,6 +35,9 @@ type ClassThermalZoneStats struct {
 	Policy  string  // One of the various thermal governors used for a particular zone.
 	Mode    *bool   // Optional: One of the predefined values in [enabled, disabled].
 	Passive *uint64 // Optional: millidegrees Celsius. (0 for disabled, > 1000 for enabled+value)
+
+	// ReadError contains any errors returned when gathering data.
+	ReadErrors error
 }
 
 // ClassThermalZoneStats returns Thermal Zone metrics for all zones.
@@ -48,39 +49,33 @@ func (fs FS) ClassThermalZoneStats() ([]ClassThermalZoneStats, error) {
 
 	stats := make([]ClassThermalZoneStats, 0, len(zones))
 	for _, zone := range zones {
-		zoneStats, err := parseClassThermalZone(zone)
-		if err != nil {
-			if errors.Is(err, syscall.ENODATA) || errors.As(err, new(*fsp.PathError)) || errors.Is(err, syscall.EAGAIN) ||
-				errors.Is(err, syscall.EINVAL) {
-				continue
-			}
-			return nil, err
-		}
+		zoneStats := parseClassThermalZone(zone)
 		zoneStats.Name = strings.TrimPrefix(filepath.Base(zone), "thermal_zone")
 		stats = append(stats, zoneStats)
 	}
 	return stats, nil
 }
 
-func parseClassThermalZone(zone string) (ClassThermalZoneStats, error) {
+func parseClassThermalZone(zone string) ClassThermalZoneStats {
+	var errs []error
 	// Required attributes.
 	zoneType, err := util.SysReadFile(filepath.Join(zone, "type"))
 	if err != nil {
-		return ClassThermalZoneStats{}, err
+		errs = append(errs, fmt.Errorf("error reading type: %w", err))
 	}
 	zonePolicy, err := util.SysReadFile(filepath.Join(zone, "policy"))
 	if err != nil {
-		return ClassThermalZoneStats{}, err
+		errs = append(errs, fmt.Errorf("error reading policy: %w", err))
 	}
 	zoneTemp, err := util.SysReadIntFromFile(filepath.Join(zone, "temp"))
-	if err != nil {
-		return ClassThermalZoneStats{}, err
+	if err != nil && !errors.Is(err, os.ErrInvalid) {
+		errs = append(errs, fmt.Errorf("error reading temp: %w", err))
 	}
 
 	// Optional attributes.
 	mode, err := util.SysReadFile(filepath.Join(zone, "mode"))
 	if err != nil && !os.IsNotExist(err) && !os.IsPermission(err) {
-		return ClassThermalZoneStats{}, err
+		errs = append(errs, fmt.Errorf("error reading mode: %w", err))
 	}
 	zoneMode := util.ParseBool(mode)
 
@@ -90,16 +85,17 @@ func parseClassThermalZone(zone string) (ClassThermalZoneStats, error) {
 	case os.IsNotExist(err), os.IsPermission(err):
 		zonePassive = nil
 	case err != nil:
-		return ClassThermalZoneStats{}, err
+		errs = append(errs, fmt.Errorf("error reading passive: %w", err))
 	default:
 		zonePassive = &passive
 	}
 
 	return ClassThermalZoneStats{
-		Type:    zoneType,
-		Policy:  zonePolicy,
-		Temp:    zoneTemp,
-		Mode:    zoneMode,
-		Passive: zonePassive,
-	}, nil
+		Type:       zoneType,
+		Policy:     zonePolicy,
+		Temp:       zoneTemp,
+		Mode:       zoneMode,
+		Passive:    zonePassive,
+		ReadErrors: errors.Join(errs...),
+	}
 }
diff --git a/sysfs/class_thermal_test.go b/sysfs/class_thermal_test.go
index 7c2a45c8..0e5feeb0 100644
--- a/sysfs/class_thermal_test.go
+++ b/sysfs/class_thermal_test.go
@@ -39,20 +39,22 @@ func TestClassThermalZoneStats(t *testing.T) {
 
 	classThermalZoneStats := []ClassThermalZoneStats{
 		{
-			Name:    "0",
-			Type:    "bcm2835_thermal",
-			Policy:  "step_wise",
-			Temp:    49925,
-			Mode:    nil,
-			Passive: nil,
+			Name:       "0",
+			Type:       "bcm2835_thermal",
+			Policy:     "step_wise",
+			Temp:       49925,
+			Mode:       nil,
+			Passive:    nil,
+			ReadErrors: nil,
 		},
 		{
-			Name:    "1",
-			Type:    "acpitz",
-			Policy:  "step_wise",
-			Temp:    -44000,
-			Mode:    enabled,
-			Passive: &passive,
+			Name:       "1",
+			Type:       "acpitz",
+			Policy:     "step_wise",
+			Temp:       -44000,
+			Mode:       enabled,
+			Passive:    &passive,
+			ReadErrors: nil,
 		},
 	}