ctdb-common: Add wait_send/wait_recv to sock_daemon_funcs

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12510

To be able to terminate the daemon from within the implementation,
create a subreq using wait_send() provided by the implementation.
When the subreq is finished, it signals the sock_daemon code to terminate
the daemon.

This avoids the need to keep track of the top level tevent_req causing
layer violation and keeps the code flow straighforward.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Stefan Metzmacher <metze@samba.org>

Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Mon Jan 16 21:16:51 CET 2017 on sn-devel-144

2 files changed, 44 insertions, 17 deletions

diff --git a/ctdb/common/sock_daemon.c b/ctdb/common/sock_daemon.c
index 3b679ab1332..b53b4d85333 100644
--- a/ctdb/common/sock_daemon.c
+++ b/ctdb/common/sock_daemon.c
@@ -70,7 +70,6 @@ struct sock_daemon_context {
 
 	struct pidfile_context *pid_ctx;
 	struct sock_socket *socket_list;
-	struct tevent_req *req;
 };
 
 /*
@@ -451,8 +450,6 @@ bool sock_socket_write_recv(struct tevent_req *req, int *perr)
  * Socket daemon
  */
 
-static int sock_daemon_context_destructor(struct sock_daemon_context *sockd);
-
 int sock_daemon_setup(TALLOC_CTX *mem_ctx, const char *daemon_name,
 		      const char *logging, const char *debug_level,
 		      const char *pidfile,
@@ -487,21 +484,10 @@ int sock_daemon_setup(TALLOC_CTX *mem_ctx, const char *daemon_name,
 		}
 	}
 
-	talloc_set_destructor(sockd, sock_daemon_context_destructor);
-
 	*out = sockd;
 	return 0;
 }
 
-static int sock_daemon_context_destructor(struct sock_daemon_context *sockd)
-{
-	if (sockd->req != NULL) {
-		tevent_req_done(sockd->req);
-	}
-
-	return 0;
-}
-
 int sock_daemon_add_unix(struct sock_daemon_context *sockd,
 			 const char *sockpath,
 			 struct sock_socket_funcs *funcs,
@@ -546,6 +532,7 @@ static void sock_daemon_run_reconfigure(struct tevent_req *req);
 static void sock_daemon_run_shutdown(struct tevent_req *req);
 static void sock_daemon_run_socket_fail(struct tevent_req *subreq);
 static void sock_daemon_run_watch_pid(struct tevent_req *subreq);
+static void sock_daemon_run_wait_done(struct tevent_req *subreq);
 
 struct tevent_req *sock_daemon_run_send(TALLOC_CTX *mem_ctx,
 					struct tevent_context *ev,
@@ -620,7 +607,16 @@ struct tevent_req *sock_daemon_run_send(TALLOC_CTX *mem_ctx,
 					req);
 	}
 
-	sockd->req = req;
+	if (sockd->funcs != NULL && sockd->funcs->wait_send != NULL &&
+	    sockd->funcs->wait_recv != NULL) {
+		subreq = sockd->funcs->wait_send(state, ev,
+						 sockd->private_data);
+		if (tevent_req_nomem(subreq, req)) {
+			return tevent_req_post(req, ev);
+		}
+		tevent_req_set_callback(subreq, sock_daemon_run_wait_done,
+					req);
+	}
 
 	return req;
 }
@@ -748,6 +744,26 @@ static void sock_daemon_run_watch_pid(struct tevent_req *subreq)
 	tevent_req_set_callback(subreq, sock_daemon_run_watch_pid, req);
 }
 
+static void sock_daemon_run_wait_done(struct tevent_req *subreq)
+{
+	struct tevent_req *req = tevent_req_callback_data(
+		subreq, struct tevent_req);
+	struct sock_daemon_run_state *state = tevent_req_data(
+		req, struct sock_daemon_run_state);
+	struct sock_daemon_context *sockd = state->sockd;
+	int ret;
+	bool status;
+
+	status = sockd->funcs->wait_recv(subreq, &ret);
+	TALLOC_FREE(subreq);
+	sock_daemon_run_shutdown(req);
+	if (! status) {
+		tevent_req_error(req, ret);
+	} else {
+		tevent_req_done(req);
+	}
+}
+
 bool sock_daemon_run_recv(struct tevent_req *req, int *perr)
 {
 	int ret;
@@ -778,7 +794,6 @@ int sock_daemon_run(struct tevent_context *ev,
 	tevent_req_poll(req, ev);
 
 	status = sock_daemon_run_recv(req, &ret);
-	sockd->req = NULL;
 	TALLOC_FREE(req);
 	if (! status) {
 		return ret;
diff --git a/ctdb/common/sock_daemon.h b/ctdb/common/sock_daemon.h
index 6c474acd021..81853f66446 100644
--- a/ctdb/common/sock_daemon.h
+++ b/ctdb/common/sock_daemon.h
@@ -50,12 +50,24 @@ struct sock_client_context;
  * startup() is called when the daemon starts running
  *            either via sock_daemon_run() or via sock_daemon_run_send()
  * reconfigure() is called when process receives SIGUSR1 or SIGHUP
- * shutdown() is called when process receives SIGINT or SIGTERM
+ * shutdown() is called when process receives SIGINT or SIGTERM or
+ *             when wait computation has finished
+ *
+ * wait_send() starts the async computation to keep running the daemon
+ * wait_recv() ends the async computation to keep running the daemon
+ *
+ * If wait_send()/wait_recv() is NULL, then daemon will keep running forever.
+ * If wait_send() returns req, then when req is over, daemon will shutdown.
  */
 struct sock_daemon_funcs {
 	void (*startup)(void *private_data);
 	void (*reconfigure)(void *private_data);
 	void (*shutdown)(void *private_data);
+
+	struct tevent_req * (*wait_send)(TALLOC_CTX *mem_ctx,
+					 struct tevent_context *ev,
+					 void *private_data);
+	bool (*wait_recv)(struct tevent_req *req, int *perr);
 };
 
 /**