From 623b99327d0ac9d47afb6562a071ca120750346f Mon Sep 17 00:00:00 2001
From: Julian Oes <julian@oes.ch>
Date: Mon, 1 Aug 2016 11:15:21 +0200
Subject: [PATCH] param: lock the bus as short as possible (#5187)

Since the FRAM and the baro are on the same bus on the Pixracer, we
currently need to lock down everything (instead of just this SPI bus)
for the time when the params are written.
Therefore, we need to keep this locking as short as possible.

This change makes the locking even shorter by moving all param_get and
param_name and param_size calls out of the lock.
---
 src/modules/systemlib/param/param.c | 68 +++++++++++++++++------------
 1 file changed, 41 insertions(+), 27 deletions(-)

diff --git a/src/modules/systemlib/param/param.c b/src/modules/systemlib/param/param.c
index 265c5f7e14..2033fe36b4 100644
--- a/src/modules/systemlib/param/param.c
+++ b/src/modules/systemlib/param/param.c
@@ -895,49 +895,63 @@ param_export(int fd, bool only_unsaved)
 
 		/* append the appropriate BSON type object */
 
-		/* lock as short as possible */
-		param_bus_lock(true);
 
 		switch (param_type(s->param)) {
 
-		case PARAM_TYPE_INT32:
-			param_get(s->param, &i);
+		case PARAM_TYPE_INT32: {
+				param_get(s->param, &i);
+				const char *name = param_name(s->param);
 
-			if (bson_encoder_append_int(&encoder, param_name(s->param), i)) {
-				debug("BSON append failed for '%s'", param_name(s->param));
-				param_bus_lock(false);
-				goto out;
+				/* lock as short as possible */
+				param_bus_lock(true);
+
+				if (bson_encoder_append_int(&encoder, name, i)) {
+					param_bus_lock(false);
+					debug("BSON append failed for '%s'", name);
+					goto out;
+				}
 			}
-
 			break;
 
-		case PARAM_TYPE_FLOAT:
-			param_get(s->param, &f);
+		case PARAM_TYPE_FLOAT: {
 
-			if (bson_encoder_append_double(&encoder, param_name(s->param), f)) {
-				debug("BSON append failed for '%s'", param_name(s->param));
-				param_bus_lock(false);
-				goto out;
+				param_get(s->param, &f);
+				const char *name = param_name(s->param);
+
+				/* lock as short as possible */
+				param_bus_lock(true);
+
+				if (bson_encoder_append_double(&encoder, name, f)) {
+					param_bus_lock(false);
+					debug("BSON append failed for '%s'", name);
+					goto out;
+				}
 			}
-
 			break;
 
-		case PARAM_TYPE_STRUCT ... PARAM_TYPE_STRUCT_MAX:
-			if (bson_encoder_append_binary(&encoder,
-						       param_name(s->param),
-						       BSON_BIN_BINARY,
-						       param_size(s->param),
-						       param_get_value_ptr(s->param))) {
-				debug("BSON append failed for '%s'", param_name(s->param));
-				param_bus_lock(false);
-				goto out;
-			}
+		case PARAM_TYPE_STRUCT ... PARAM_TYPE_STRUCT_MAX: {
 
+				const char *name = param_name(s->param);
+				const size_t size = param_size(s->param);
+				const void *value_ptr = param_get_value_ptr(s->param);
+
+				/* lock as short as possible */
+				param_bus_lock(true);
+
+				if (bson_encoder_append_binary(&encoder,
+							       name,
+							       BSON_BIN_BINARY,
+							       size,
+							       value_ptr)) {
+					param_bus_lock(false);
+					debug("BSON append failed for '%s'", name);
+					goto out;
+				}
+			}
 			break;
 
 		default:
 			debug("unrecognized parameter type");
-			param_bus_lock(false);
 			goto out;
 		}