param: grab the shutdown lock while writing params to the file

src/modules/systemlib/flashparams/flashparams.c

@@ -44,6 +44,7 @@
 
 #include <px4_defines.h>
 #include <px4_posix.h>
+#include <px4_shutdown.h>
 #include <string.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -158,6 +159,12 @@ out:
 
 		size_t buf_size = bson_encoder_buf_size(&encoder);
 
+		int shutdown_lock_ret = px4_shutdown_lock();
+
+		if (shutdown_lock_ret) {
+			PX4_ERR("px4_shutdown_lock() failed (%i)", shutdown_lock_ret);
+		}
+
 		/* Get a buffer from the flash driver with enough space */
 
 		uint8_t *buffer;
@@ -186,6 +193,11 @@ out:
 			free(enc_buff);
 			parameter_flashfs_free();
 		}
+
+		if (shutdown_lock_ret == 0) {
+			px4_shutdown_unlock();
+		}
+
 	}
 
 	return result;

src/modules/systemlib/param/param.c

@@ -45,6 +45,7 @@
 #include <px4_defines.h>
 #include <px4_posix.h>
 #include <px4_config.h>
+#include <px4_shutdown.h>
 #include <string.h>
 #include <stdbool.h>
 #include <float.h>
@@ -1003,6 +1004,12 @@ param_export(int fd, bool only_unsaved)
 	struct bson_encoder_s encoder;
 	int	result = -1;
 
+	int shutdown_lock_ret = px4_shutdown_lock();
+
+	if (shutdown_lock_ret) {
+		PX4_ERR("px4_shutdown_lock() failed (%i)", shutdown_lock_ret);
+	}
+
 	param_lock_writer();
 
 	bson_encoder_init_file(&encoder, fd);
@@ -1090,6 +1097,12 @@ param_export(int fd, bool only_unsaved)
 out:
 	param_unlock_writer();
 
+	fsync(fd); // make sure the data is flushed before releasing the shutdown lock
+
+	if (shutdown_lock_ret == 0) {
+		px4_shutdown_unlock();
+	}
+
 	if (result == 0) {
 		result = bson_encoder_fini(&encoder);
 	}

src/modules/systemlib/param/param_shmem.c

@@ -44,6 +44,7 @@
 //#include <debug.h>
 #include <px4_defines.h>
 #include <px4_posix.h>
+#include <px4_shutdown.h>
 #include <string.h>
 #include <stdbool.h>
 #include <stdlib.h>
@@ -945,14 +946,6 @@ param_save_default(void)
 		goto exit;
 	}
 
-	// After writing the file, also do a fsync to prevent loosing params if power is cut.
-	res = fsync(fd);
-
-	if (res != 0) {
-		PX4_ERR("failed to do fsync: %s", strerror(errno));
-		goto exit;
-	}
-
 	PARAM_CLOSE(fd);
 
 
@@ -1044,6 +1037,12 @@ param_export(int fd, bool only_unsaved)
 	struct bson_encoder_s encoder;
 	int	result = -1;
 
+	int shutdown_lock_ret = px4_shutdown_lock();
+
+	if (shutdown_lock_ret) {
+		PX4_ERR("px4_shutdown_lock() failed (%i)", shutdown_lock_ret);
+	}
+
 	param_lock();
 
 	bson_encoder_init_file(&encoder, fd);
@@ -1123,6 +1122,12 @@ param_export(int fd, bool only_unsaved)
 out:
 	param_unlock();
 
+	fsync(fd); // make sure the data is flushed before releasing the shutdown lock
+
+	if (shutdown_lock_ret == 0) {
+		px4_shutdown_unlock();
+	}
+
 	if (result == 0) {
 		result = bson_encoder_fini(&encoder);
 	}