From 210c19999fbca15d5540588e1361917204d0dd7a Mon Sep 17 00:00:00 2001
From: Florian Lehner <florian.lehner@elastic.co>
Date: Mon, 6 Nov 2023 13:47:06 +0100
Subject: [PATCH] replace sync.Map with custom struct with sync.RWMutex

Signed-off-by: Florian Lehner <florian.lehner@elastic.co>
---
 metric/system/cgroup/reader.go |  8 +++++++-
 metric/system/cgroup/util.go   | 31 +++++++++++++++++--------------
 2 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/metric/system/cgroup/reader.go b/metric/system/cgroup/reader.go
index 5fbd840ba9..f9bb6bb86c 100644
--- a/metric/system/cgroup/reader.go
+++ b/metric/system/cgroup/reader.go
@@ -85,6 +85,11 @@ type pathListWithTime struct {
 	pathList PathList
 }
 
+type pathCache struct {
+	sync.RWMutex
+	cache map[string]pathListWithTime
+}
+
 // Reader reads cgroup metrics and limits.
 type Reader struct {
 	// Mountpoint of the root filesystem. Defaults to / if not set. This can be
@@ -95,7 +100,7 @@ type Reader struct {
 	cgroupMountpoints        Mountpoints // Mountpoints for each subsystem (e.g. cpu, cpuacct, memory, blkio).
 
 	// Cache to map known v2 cgroup controllerPaths to pathListWithTime.
-	v2ControllerPathCache sync.Map
+	v2ControllerPathCache pathCache
 }
 
 // ReaderOptions holds options for NewReaderOptions.
@@ -146,6 +151,7 @@ func NewReaderOptions(opts ReaderOptions) (*Reader, error) {
 		ignoreRootCgroups:        opts.IgnoreRootCgroups,
 		cgroupsHierarchyOverride: opts.CgroupsHierarchyOverride,
 		cgroupMountpoints:        mountpoints,
+		v2ControllerPathCache:    pathCache{cache: make(map[string]pathListWithTime)},
 	}, nil
 }
 
diff --git a/metric/system/cgroup/util.go b/metric/system/cgroup/util.go
index 8a9329bdb9..95942b7a83 100644
--- a/metric/system/cgroup/util.go
+++ b/metric/system/cgroup/util.go
@@ -278,20 +278,21 @@ the container as /sys/fs/cgroup/unified and start the system module with the hos
 			}
 
 			// Check if there is an entry for controllerPath already cached.
-			if tmp, ok := r.v2ControllerPathCache.Load(controllerPath); ok {
-				cacheEntry, ok := tmp.(pathListWithTime)
-				if ok {
-					// If the cached entry for controllerPath is not older than 5 minutes,
-					// return the cached entry.
-					if time.Since(cacheEntry.added) < time.Duration(5*time.Minute) {
-						cPaths.V2 = cacheEntry.pathList.V2
-						continue
-					}
+			r.v2ControllerPathCache.Lock()
+			cacheEntry, ok := r.v2ControllerPathCache.cache[controllerPath]
+			if ok {
+				// If the cached entry for controllerPath is not older than 5 minutes,
+				// return the cached entry.
+				if time.Since(cacheEntry.added) < 5*time.Minute {
+					cPaths.V2 = cacheEntry.pathList.V2
+					r.v2ControllerPathCache.Unlock()
+					continue
 				}
-				// Consider the existing entry for controllerPath invalid. The entry can
-				// (1) not be casted to pathListWithTime or (2) is older than 5 minutes.
-				r.v2ControllerPathCache.Delete(controllerPath)
 			}
+			// Consider the existing entry for controllerPath invalid, as it is
+			// older than 5 minutes.
+			delete(r.v2ControllerPathCache.cache, controllerPath)
+			r.v2ControllerPathCache.Unlock()
 
 			cgpaths, err := os.ReadDir(controllerPath)
 			if err != nil {
@@ -305,10 +306,12 @@ the container as /sys/fs/cgroup/unified and start the system module with the hos
 					cPaths.V2[controllerName] = ControllerPath{ControllerPath: path, FullPath: controllerPath, IsV2: true}
 				}
 			}
-			r.v2ControllerPathCache.Store(controllerPath, pathListWithTime{
+			r.v2ControllerPathCache.Lock()
+			r.v2ControllerPathCache.cache[controllerPath] = pathListWithTime{
 				added:    time.Now(),
 				pathList: cPaths,
-			})
+			}
+			r.v2ControllerPathCache.Unlock()
 			// cgroup v1
 		} else {
 			subsystems := strings.Split(fields[1], ",")