Add collector for hung_task_detect_count (#3470)

* Add collector for hung_task_detect_count

---------

Signed-off-by: ScarletBlizzard <[email protected]>

Author: ScarletBlizzard

README.md

@@ -195,6 +195,7 @@ drm | Expose GPU metrics using sysfs / DRM, `amdgpu` is the only driver which ex
 drbd | Exposes Distributed Replicated Block Device statistics (to version 8.4) | Linux
 ethtool | Exposes network interface information and network driver statistics equivalent to `ethtool`, `ethtool -S`, and `ethtool -i`. | Linux
 interrupts | Exposes detailed interrupts statistics. | Linux, OpenBSD
+kernel_hung | Exposes number of tasks that have been detected as hung from `/proc/sys/kernel/hung_task_detect_count`. | Linux
 ksmd | Exposes kernel and system statistics from `/sys/kernel/mm/ksm`. | Linux
 lnstat | Exposes stats from `/proc/net/stat/`. | Linux
 logind | Exposes session counts from [logind](http://www.freedesktop.org/wiki/Software/systemd/logind/). | Linux

collector/kernel_hung_linux.go

@@ -0,0 +1,63 @@
+// Copyright 2018 The Prometheus Authors
+// 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.
+
+//go:build !noprocesses
+
+package collector
+
+import (
+	"fmt"
+	"log/slog"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs"
+)
+
+type kernelHungCollector struct {
+	fs     procfs.FS
+	logger *slog.Logger
+}
+
+func init() {
+	registerCollector("kernel_hung", defaultDisabled, NewKernelHungCollector)
+}
+
+func NewKernelHungCollector(logger *slog.Logger) (Collector, error) {
+	fs, err := procfs.NewFS(*procPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open procfs: %w", err)
+	}
+	return &kernelHungCollector{
+		fs:     fs,
+		logger: logger,
+	}, nil
+}
+
+var (
+	taskDetectCount = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "kernel_hung", "task_detect_count"),
+		"Total number of interrupts serviced.",
+		nil, nil,
+	)
+)
+
+func (c *kernelHungCollector) Update(ch chan<- prometheus.Metric) error {
+	kernelHung, err := c.fs.KernelHung()
+	if err != nil {
+		return err
+	}
+
+	ch <- prometheus.MustNewConstMetric(taskDetectCount, prometheus.CounterValue, float64(*kernelHung.HungTaskDetectCount))
+
+	return nil
+}