Ensure shutdown handler access is syncronized

There was a potential race where two handlers could be added at
the same time. Go Maps are not thread-safe, so that could do
unpleasant things. Add a mutex to keep things safe.

Also, swap the order or Register and Start for the handlers in
Libpod runtime created. As written, there was a small gap between
Start and Register where SIGTERM/SIGINT would be completely
ignored, instead of stopping Podman. Swapping the two closes this
gap.

Signed-off-by: Matthew Heon <mheon@redhat.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/pkg/api/server/server.go b/pkg/api/server/server.go
index 046f6561c..d612041f6 100644
--- a/pkg/api/server/server.go
+++ b/pkg/api/server/server.go
@@ -179,15 +179,15 @@ func setupSystemd() {
 func (s *APIServer) Serve() error {
 	setupSystemd()
 
-	// Start the shutdown signal handler.
-	if err := shutdown.Start(); err != nil {
-		return err
-	}
 	if err := shutdown.Register("server", func(sig os.Signal) error {
 		return s.Shutdown()
 	}); err != nil {
 		return err
 	}
+	// Start the shutdown signal handler.
+	if err := shutdown.Start(); err != nil {
+		return err
+	}
 
 	errChan := make(chan error, 1)