[release/1.6] metrics/cgroups: fix deadlock issue in Add during Collect

[fuweid]

The Collector.Collect will be the field ns'Collect's callback, which be
invoked periodically with internal lock. And Collector.Add also runs
with ns.Lock in Collector.Lock, which is easy to cause deadlock.

Goroutine X:

ns.Collect
  ns.Lock
    Collector.Collect
      Collector.RLock

Goroutine Y:

Collector.Add
  Collector.Lock
    ns.Lock

We should use ns.Lock without Collector.Lock in Add.

Fix: #6772

Signed-off-by: Wei Fu fuweid89@gmail.com
(cherry picked from commit 8a1280b)
Signed-off-by: Wei Fu fuweid89@gmail.com

---

🍒 from #6788
And updated Stats mock interface because of the protobuf dependency.

diff --git a/metrics/cgroups/metrics_test.go b/metrics/cgroups/metrics_test.go
index c362ea3b9..c71ea60a5 100644
--- a/metrics/cgroups/metrics_test.go
+++ b/metrics/cgroups/metrics_test.go
@@ -32,7 +32,7 @@ import (
        v2 "github.com/containerd/containerd/metrics/cgroups/v2"
        v1types "github.com/containerd/containerd/metrics/types/v1"
        v2types "github.com/containerd/containerd/metrics/types/v2"
-       "github.com/containerd/containerd/protobuf"
+       "github.com/containerd/typeurl"
        "github.com/prometheus/client_golang/prometheus"
 
        metrics "github.com/docker/go-metrics"
@@ -152,7 +152,7 @@ func (t *mockStatT) Namespace() string {
 
 func (t *mockStatT) Stats(context.Context) (*types.Any, error) {
        if t.isV1 {
-               return protobuf.MarshalAnyToProto(&v1types.Metrics{})
+               return typeurl.MarshalAny(&v1types.Metrics{})
        }
-       return protobuf.MarshalAnyToProto(&v2types.Metrics{})
+       return typeurl.MarshalAny(&v2types.Metrics{})
 }

[estesp]

LGTM

[uthark]

When do you plan 1.6.3 with the fix?