Revert "remove static_lock()/static_unlock() and start to use thread local storage (v2)"

src/lxc/lxclock.c

@@ -44,6 +44,7 @@ lxc_log_define(lxc_lock, lxc);
 
 #ifdef MUTEX_DEBUGGING
 pthread_mutex_t thread_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
+pthread_mutex_t static_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
 
 inline void dump_stacktrace(void)
 {
@@ -65,6 +66,7 @@ inline void dump_stacktrace(void)
 }
 #else
 pthread_mutex_t thread_mutex = PTHREAD_MUTEX_INITIALIZER;
+pthread_mutex_t static_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 inline void dump_stacktrace(void) {;}
 #endif
@@ -322,6 +324,17 @@ void process_unlock(void)
 	unlock_mutex(&thread_mutex);
 }
 
+/* Protects static const values inside the lxc_global_config_value funtion */
+void static_lock(void)
+{
+	lock_mutex(&static_mutex);
+}
+
+void static_unlock(void)
+{
+	unlock_mutex(&static_mutex);
+}
+
 int container_mem_lock(struct lxc_container *c)
 {
 	return lxclock(c->privlock, 0);

src/lxc/lxclock.h

@@ -123,6 +123,16 @@ extern void process_lock(void);
  */
 extern void process_unlock(void);
 
+/*!
+ * \brief Lock global data.
+ */
+extern void static_lock(void);
+
+/*!
+ * \brief Unlock global data.
+ */
+extern void static_unlock(void);
+
 struct lxc_container;
 
 /*!

src/lxc/utils.c

@@ -254,6 +254,9 @@ const char *lxc_global_config_value(const char *option_name)
 		{ NULL, NULL },
 	};
 
+	/* Protected by a mutex to eliminate conflicting load and store operations */
+	static const char *values[sizeof(options) / sizeof(options[0])] = { 0 };
+
 	char *user_config_path = NULL;
 	char *user_lxc_path = NULL;
 	char *user_home = NULL;
@@ -278,8 +281,6 @@ const char *lxc_global_config_value(const char *option_name)
 		user_lxc_path = strdup(LXCPATH);
 	}
 
-	/* placed in the thread local storage pool */
-	static __thread const char *values[sizeof(options) / sizeof(options[0])] = { 0 };
 	const char *(*ptr)[2];
 	const char *value;
 	size_t i;
@@ -297,13 +298,15 @@ const char *lxc_global_config_value(const char *option_name)
 		return NULL;
 	}
 
+	static_lock();
 	if (values[i]) {
 		free(user_config_path);
 		free(user_lxc_path);
 		value = values[i];
-
+		static_unlock();
 		return value;
 	}
+	static_unlock();
 
 	process_lock();
 	fin = fopen_cloexec(user_config_path, "r");
@@ -341,12 +344,15 @@ const char *lxc_global_config_value(const char *option_name)
 			while (*p && (*p == ' ' || *p == '\t')) p++;
 			if (!*p)
 				continue;
+			static_lock();
 			values[i] = copy_global_config_value(p);
+			static_unlock();
 			free(user_lxc_path);
 			goto out;
 		}
 	}
 	/* could not find value, use default */
+	static_lock();
 	if (strcmp(option_name, "lxcpath") == 0)
 		values[i] = user_lxc_path;
 	else {
@@ -358,6 +364,7 @@ const char *lxc_global_config_value(const char *option_name)
 	 * as an error... */
 	if (!values[i])
 		errno = 0;
+	static_unlock();
 
 out:
 	process_lock();
@@ -365,7 +372,10 @@ out:
 		fclose(fin);
 	process_unlock();
 
-	return values[i];
+	static_lock();
+	value = values[i];
+	static_unlock();
+	return value;
 }
 
 const char *default_lvm_vg(void)