logs -f: file: fix dead lock

Fix a dead lock in the file log driver where one goroutine would wait on
the tail to hit EOF but reading is blocked for the function to return.

Fixes: 11461
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

2 files changed, 36 insertions, 7 deletions

diff --git a/libpod/container_log.go b/libpod/container_log.go
index 3988bb654..89dd5e8b0 100644
--- a/libpod/container_log.go
+++ b/libpod/container_log.go
@@ -107,16 +107,18 @@ func (c *Container) readFromLogFile(ctx context.Context, options *logs.LogOption
 		// until EOF.
 		state, err := c.State()
 		if err != nil || state != define.ContainerStateRunning {
-			// Make sure to wait at least for the poll duration
-			// before stopping the file logger (see #10675).
-			time.Sleep(watch.POLL_DURATION)
-			tailError := t.StopAtEOF()
-			if tailError != nil && fmt.Sprintf("%v", tailError) != "tail: stop at eof" {
-				logrus.Errorf("Error stopping logger: %v", tailError)
-			}
 			if err != nil && errors.Cause(err) != define.ErrNoSuchCtr {
 				logrus.Errorf("Error getting container state: %v", err)
 			}
+			go func() {
+				// Make sure to wait at least for the poll duration
+				// before stopping the file logger (see #10675).
+				time.Sleep(watch.POLL_DURATION)
+				tailError := t.StopAtEOF()
+				if tailError != nil && tailError.Error() != "tail: stop at eof" {
+					logrus.Errorf("Error stopping logger: %v", tailError)
+				}
+			}()
 			return nil
 		}
 
diff --git a/test/system/035-logs.bats b/test/system/035-logs.bats
index 32282c8e1..a04d2ac74 100644
--- a/test/system/035-logs.bats
+++ b/test/system/035-logs.bats
@@ -174,4 +174,31 @@ $s_after"
     _log_test_until journald
 }
 
+function _log_test_follow() {
+    local driver=$1
+    cname=$(random_string)
+    contentA=$(random_string)
+    contentB=$(random_string)
+    contentC=$(random_string)
+
+    # Note: it seems we need at least three log lines to hit #11461.
+    run_podman run --log-driver=$driver --name $cname $IMAGE sh -c "echo $contentA; echo $contentB; echo $contentC"
+    run_podman logs -f $cname
+    is "$output" "$contentA
+$contentB
+$contentC" "logs -f on exitted container works"
+
+    run_podman rm -f $cname
+}
+
+@test "podman logs - --follow k8s-file" {
+    _log_test_follow k8s-file
+}
+
+@test "podman logs - --follow journald" {
+    # We can't use journald on RHEL as rootless: rhbz#1895105
+    skip_if_journald_unavailable
+
+    _log_test_follow journald
+}
 # vim: filetype=sh