sdnotify: send MAINPID only once

Send the main PID only once.  Previously, `(*Container).start()` and
the conmon handler sent them ~simultaneously and went into a race.

I noticed the issue while debugging a WIP PR.

Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>

2 files changed, 5 insertions, 20 deletions

diff --git a/libpod/oci_conmon_linux.go b/libpod/oci_conmon_linux.go
index c232702e9..6aa7ce6dc 100644
--- a/libpod/oci_conmon_linux.go
+++ b/libpod/oci_conmon_linux.go
@@ -36,7 +36,6 @@ import (
 	"github.com/containers/podman/v4/utils"
 	"github.com/containers/storage/pkg/homedir"
 	pmount "github.com/containers/storage/pkg/mount"
-	"github.com/coreos/go-systemd/v22/daemon"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/opencontainers/selinux/go-selinux/label"
 	"github.com/pkg/errors"
@@ -1279,19 +1278,6 @@ func (r *ConmonOCIRuntime) createOCIContainer(ctr *Container, restoreOptions *Co
 		// conmon not having a pid file is a valid state, so don't set it if we don't have it
 		logrus.Infof("Got Conmon PID as %d", conmonPID)
 		ctr.state.ConmonPID = conmonPID
-
-		// Send the MAINPID via sdnotify if needed.
-		switch ctr.config.SdNotifyMode {
-		case define.SdNotifyModeContainer, define.SdNotifyModeIgnore:
-		// Nothing to do or conmon takes care of it already.
-
-		default:
-			if sent, err := daemon.SdNotify(false, fmt.Sprintf("MAINPID=%d", conmonPID)); err != nil {
-				logrus.Errorf("Notifying systemd of Conmon PID: %v", err)
-			} else if sent {
-				logrus.Debugf("Notify MAINPID sent successfully")
-			}
-		}
 	}
 
 	runtimeRestoreDuration := func() int64 {
diff --git a/test/system/260-sdnotify.bats b/test/system/260-sdnotify.bats
index 395e6f94f..88d84c86f 100644
--- a/test/system/260-sdnotify.bats
+++ b/test/system/260-sdnotify.bats
@@ -106,6 +106,9 @@ function _assert_mainpid_is_conmon() {
     cid="$output"
     wait_for_ready $cid
 
+    run_podman container inspect sdnotify_conmon_c --format "{{.State.ConmonPid}}"
+    mainPID="$output"
+
     run_podman logs sdnotify_conmon_c
     is "$output" "READY" "\$NOTIFY_SOCKET in container"
 
@@ -114,12 +117,8 @@ function _assert_mainpid_is_conmon() {
     echo "socat log:"
     echo "$output"
 
-    # ARGH! 'READY=1' should always be the last output line. But sometimes,
-    # for reasons unknown, we get an extra MAINPID=xxx after READY=1 (#8718).
-    # Who knows if this is a systemd bug, or conmon, or what. I don't
-    # even know where to begin asking. So, to eliminate the test flakes,
-    # we look for READY=1 _anywhere_ in the output, not just the last line.
-    is "$output" ".*READY=1.*" "sdnotify sent READY=1"
+    is "$output" "MAINPID=$mainPID
+READY=1" "sdnotify sent MAINPID and READY"
 
     _assert_mainpid_is_conmon "$output"