container stats: fix --no-stream race

Fix a race in `podman container stats` by waiting for the client to
consume the data in the channel.  This requires a `sync.WaitGroup` (or
semaphore) in the client and to also close the channel the backend.

Fixes: #6405
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

cmd/podman/containers/stats.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"strings"
+	"sync"
 	"text/tabwriter"
 	"text/template"
 
@@ -111,14 +112,20 @@ func stats(cmd *cobra.Command, args []string) error {
 		}
 	}
 	statsOptions.StatChan = make(chan []*define.ContainerStats, 1)
+	wg := sync.WaitGroup{}
+	wg.Add(1)
 	go func() {
 		for reports := range statsOptions.StatChan {
 			if err := outputStats(reports); err != nil {
 				logrus.Error(err)
 			}
 		}
+		wg.Done()
+
 	}()
-	return registry.ContainerEngine().ContainerStats(registry.Context(), args, statsOptions)
+	err := registry.ContainerEngine().ContainerStats(registry.Context(), args, statsOptions)
+	wg.Wait()
+	return err
 }
 
 func outputStats(reports []*define.ContainerStats) error {

pkg/domain/infra/abi/containers.go

@@ -1087,6 +1087,7 @@ func (ic *ContainerEngine) Shutdown(_ context.Context) {
 }
 
 func (ic *ContainerEngine) ContainerStats(ctx context.Context, namesOrIds []string, options entities.ContainerStatsOptions) error {
+	defer close(options.StatChan)
 	containerFunc := ic.Libpod.GetRunningContainers
 	switch {
 	case len(namesOrIds) > 0: