s4: process_prefork: Make prefork_restart() use an asynchronous timer event instead of calling sleep(X).

This should prevent any long pauses in the calling process, as we get a callback
for the restart after X seconds. To make the code flow more understandable,
always go through a timer event even if the wait time is zero. This
has the same effect as an immediate event as it will call the callback
function as soon as we go back into the event loop.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>

Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Oct  2 01:38:43 UTC 2021 on sn-devel-184

1 files changed, 62 insertions, 16 deletions

diff --git a/source4/samba/process_prefork.c b/source4/samba/process_prefork.c
index 6a2e3a0acfe..f2927efbb06 100644
--- a/source4/samba/process_prefork.c
+++ b/source4/samba/process_prefork.c
@@ -426,16 +426,62 @@ static void prefork_fork_master(
 	exit(0);
 }
 
+static void prefork_restart_fn(struct tevent_context *ev,
+			       struct tevent_timer *te,
+			       struct timeval tv,
+			       void *private_data);
+
 /*
  * Restarts a child process if it exits unexpectedly
  */
-static void prefork_restart(struct tevent_context *ev,
+static bool prefork_restart(struct tevent_context *ev,
 			    struct restart_context *rc)
 {
+	struct tevent_timer *te = NULL;
+
+	if (rc->restart_delay > 0) {
+		DBG_ERR("Restarting [%s] pre-fork %s in (%d) seconds\n",
+			rc->service_name,
+			(rc->master == NULL) ? "worker" : "master",
+			rc->restart_delay);
+	}
+
+	/*
+	 * Always use an async timer event. If
+	 * rc->restart_delay is zero this is the
+	 * same as an immediate event and will be
+	 * called immediately we go back into the
+	 * event loop.
+	 */
+	te = tevent_add_timer(ev,
+			      ev,
+			      tevent_timeval_current_ofs(rc->restart_delay, 0),
+			      prefork_restart_fn,
+			      rc);
+	if (te == NULL) {
+		DBG_ERR("tevent_add_timer fail [%s] pre-fork event %s\n",
+			rc->service_name,
+			(rc->master == NULL) ? "worker" : "master");
+		/* Caller needs to free rc. */
+		return false;
+	}
+	/* Caller must not free rc - it's in use. */
+	return true;
+}
+
+static void prefork_restart_fn(struct tevent_context *ev,
+			       struct tevent_timer *te,
+			       struct timeval tv,
+			       void *private_data)
+{
 	unsigned max_backoff = 0;
 	unsigned backoff = 0;
-	unsigned restart_delay = rc->restart_delay;
 	unsigned default_value = 0;
+	struct restart_context *rc = talloc_get_type(private_data,
+					struct restart_context);
+	unsigned restart_delay = rc->restart_delay;
+
+	TALLOC_FREE(te);
 
 	/*
 	 * If the child process is constantly exiting, then restarting it can
@@ -456,13 +502,6 @@ static void prefork_restart(struct tevent_context *ev,
 				     rc->service_name,
 				     default_value);
 
-	if (restart_delay > 0) {
-		DBG_ERR("Restarting [%s] pre-fork %s in (%d) seconds\n",
-			rc->service_name,
-			(rc->master == NULL) ? "worker" : "master",
-			restart_delay);
-		sleep(restart_delay);
-	}
 	restart_delay += backoff;
 	restart_delay = min(restart_delay, max_backoff);
 
@@ -492,6 +531,10 @@ static void prefork_restart(struct tevent_context *ev,
 				    restart_delay,
 				    &pd);
 	}
+	/* tfork allocates tfork structures with malloc */
+	tfork_destroy(&rc->t);
+	free(rc->t);
+	TALLOC_FREE(rc);
 }
 
 /*
@@ -509,6 +552,7 @@ static void prefork_child_pipe_handler(struct tevent_context *ev,
 	struct restart_context *rc = NULL;
 	int status = 0;
 	pid_t pid = 0;
+	bool rc_inuse = false;
 
 	/* free the fde which removes the event and stops it firing again */
 	TALLOC_FREE(fde);
@@ -525,13 +569,13 @@ static void prefork_child_pipe_handler(struct tevent_context *ev,
 		DBG_ERR("Parent %d, Child %d terminated, "
 			"unable to get status code from tfork\n",
 			getpid(), pid);
-		prefork_restart(ev, rc);
+		rc_inuse = prefork_restart(ev, rc);
 	} else if (WIFEXITED(status)) {
 		status = WEXITSTATUS(status);
 		DBG_ERR("Parent %d, Child %d exited with status %d\n",
 			 getpid(), pid,  status);
 		if (status != 0) {
-			prefork_restart(ev, rc);
+			rc_inuse = prefork_restart(ev, rc);
 		}
 	} else if (WIFSIGNALED(status)) {
 		status = WTERMSIG(status);
@@ -541,13 +585,15 @@ static void prefork_child_pipe_handler(struct tevent_context *ev,
 		    status == SIGILL || status == SIGSYS || status == SIGSEGV ||
 		    status == SIGKILL) {
 
-			prefork_restart(ev, rc);
+			rc_inuse = prefork_restart(ev, rc);
 		}
 	}
-	/* tfork allocates tfork structures with malloc */
-	tfork_destroy(&rc->t);
-	free(rc->t);
-	TALLOC_FREE(rc);
+	if (!rc_inuse) {
+		/* tfork allocates tfork structures with malloc */
+		tfork_destroy(&rc->t);
+		free(rc->t);
+		TALLOC_FREE(rc);
+	}
 	return;
 }