[Asterisk-Dev] Variables - Race Condition

[Daniel Bichara]

Hi all,

I am testing * running with multiple channels. In my tests, using lot of 
variables (global and locals) with extensions and contexts, I found a 
potencial race condition while updating variables values and/or getting it.

I produced the attached patch that eliminated segmentation faults during 
my tests. Running it with 30 channels there was no performance penalties.

Daniel
-------------- next part --------------
--- asterisk-0.7.1/pbx.c	2004-05-19 20:07:44.000000000 +0000
+++ asterisk-0.7.1.new/pbx.c	2004-05-11 16:02:21.000000000 +0000
@@ -348,6 +348,8 @@
 
 };
 
+static ast_mutex_t varlock = AST_MUTEX_INITIALIZER;
+
 /* Lock for the application list */
 static ast_mutex_t applock = AST_MUTEX_INITIALIZER;
 static struct ast_context *contexts = NULL;
@@ -889,6 +891,7 @@
           *ret = workspace;
 	} else {
 		if (c) {
+			ast_mutex_lock(&varlock);
 			AST_LIST_TRAVERSE(headp,variables,entries) {
 #if 0
 				ast_log(LOG_WARNING,"Comparing variable '%s' with '%s'\n",var,ast_var_name(variables));
@@ -901,9 +904,11 @@
 					}
 				}
 			}
+			ast_mutex_unlock(&varlock);
 		}
 		if (!(*ret)) {
 			/* Try globals */
+			ast_mutex_lock(&varlock);
 			AST_LIST_TRAVERSE(&globals,variables,entries) {
 #if 0
 				ast_log(LOG_WARNING,"Comparing variable '%s' with '%s'\n",var,ast_var_name(variables));
@@ -916,6 +921,7 @@
 					}
 				}
 			}
+			ast_mutex_unlock(&varlock);
 		}
 		if (!(*ret)) {
 			int len=strlen(var);
@@ -4384,6 +4390,7 @@
 char *pbx_builtin_getvar_helper(struct ast_channel *chan, char *name) {
 	struct ast_var_t *variables;
 	struct varshead *headp;
+	char *ret;
 
     if (chan)
         headp=&chan->varshead;
@@ -4391,18 +4398,26 @@
 		headp=&globals;
 
 	if (name) {
+		ast_mutex_lock(&varlock);
 		AST_LIST_TRAVERSE(headp,variables,entries) {
-			if (!strcmp(name, ast_var_name(variables)))
-				return ast_var_value(variables);
+			if (!strcmp(name, ast_var_name(variables))){
+				ret=ast_var_value(variables);
+				ast_mutex_unlock(&varlock);
+				return ret;
+			}
 		}
 		if (headp != &globals) {
 			/* Check global variables if we haven't already */
 			headp = &globals;
 			AST_LIST_TRAVERSE(headp,variables,entries) {
-				if (!strcmp(name, ast_var_name(variables)))
-					return ast_var_value(variables);
+				if (!strcmp(name, ast_var_name(variables))) {
+					ret=ast_var_value(variables);
+					ast_mutex_unlock(&varlock);
+					return ret;
+				}
 			}
 		}
+		ast_mutex_unlock(&varlock);
 	}
 	return NULL;
 }
@@ -4414,6 +4429,8 @@
         headp=&chan->varshead;
 	else
 		headp=&globals;
+
+	ast_mutex_lock(&varlock);
                 
 	AST_LIST_TRAVERSE (headp,newvariable,entries) {
 		if (strcasecmp(ast_var_name(newvariable),name)==0) {
@@ -4430,6 +4447,7 @@
 		newvariable=ast_var_assign(name,value);	
 		AST_LIST_INSERT_HEAD(headp,newvariable,entries);
 	}
+	ast_mutex_unlock(&varlock);
 }
 
 int pbx_builtin_setvar(struct ast_channel *chan, void *data)