From 6359c8c008a4ecfa12c66dd94d145aa86fb14be5 Mon Sep 17 00:00:00 2001
From: Daniel Agar <daniel@agar.ca>
Date: Mon, 25 Apr 2022 11:53:22 -0400
Subject: [PATCH] mavlink: shell expand locking (#19308)

 - on some H7 boards (cuav x7pro tested) there's an occasional hard fault when starting the mavlink shell that is no longer reproducible with the slightly expanded locking
 - this is likely just changing the timing (holding the sched lock for longer), but this should be harmless for now until we can identify the root cause
---
 src/modules/mavlink/mavlink_main.cpp  | 14 ++++++++------
 src/modules/mavlink/mavlink_shell.cpp |  8 ++++----
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/modules/mavlink/mavlink_main.cpp b/src/modules/mavlink/mavlink_main.cpp
index d6ee7dd7a4..26b159829e 100644
--- a/src/modules/mavlink/mavlink_main.cpp
+++ b/src/modules/mavlink/mavlink_main.cpp
@@ -1334,18 +1334,20 @@ MavlinkShell *
 Mavlink::get_shell()
 {
 	if (!_mavlink_shell) {
-		_mavlink_shell = new MavlinkShell();
+		MavlinkShell *shell = new MavlinkShell();
 
-		if (!_mavlink_shell) {
+		if (!shell) {
 			PX4_ERR("Failed to allocate a shell");
 
 		} else {
-			int ret = _mavlink_shell->start();
+			int ret = shell->start();
 
-			if (ret != 0) {
+			if (ret == 0) {
+				_mavlink_shell = shell;
+
+			} else {
 				PX4_ERR("Failed to start shell (%i)", ret);
-				delete _mavlink_shell;
-				_mavlink_shell = nullptr;
+				delete shell;
 			}
 		}
 	}
diff --git a/src/modules/mavlink/mavlink_shell.cpp b/src/modules/mavlink/mavlink_shell.cpp
index 6203e0f28e..f0feafa623 100644
--- a/src/modules/mavlink/mavlink_shell.cpp
+++ b/src/modules/mavlink/mavlink_shell.cpp
@@ -148,14 +148,14 @@ int MavlinkShell::start()
 		close(fd_backups[i]);
 	}
 
-#ifdef __PX4_NUTTX
-	sched_unlock();
-#endif /* __PX4_NUTTX */
-
 	//close unused pipe fd's
 	close(_shell_fds[0]);
 	close(_shell_fds[1]);
 
+#ifdef __PX4_NUTTX
+	sched_unlock();
+#endif /* __PX4_NUTTX */
+
 	return ret;
 }