From: Jeremy Kerr <jk@ozlabs.org>
Date: Thu, 17 Oct 2013 04:03:51 +0000 (+0800)
Subject: ui/common: Don't talloc_free sysinfo and status explicitly
X-Git-Tag: v1.0.0~349
X-Git-Url: http://git.ozlabs.org/?p=petitboot;a=commitdiff_plain;h=a0d9a2ebdf8265d40d51f47aa55c627c0e6decd3;ds=sidebyside

ui/common: Don't talloc_free sysinfo and status explicitly

Currently, we talloc_free() the sysinfo and status messages in the
discover client, right after performing the ui's callback.

However, the client may wish to keep a reference to this information
beyond the callback invocation. This change introduces a per-message
talloc context, which these structures are allocated under. This allows
the callbacks to talloc_steal() anything they wish to keep a reference
to.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
---

diff --git a/ui/common/discover-client.c b/ui/common/discover-client.c
index de210bd..b48d541 100644
--- a/ui/common/discover-client.c
+++ b/ui/common/discover-client.c
@@ -115,7 +115,6 @@ static void update_status(struct discover_client *client,
 {
 	if (client->ops.update_status)
 		client->ops.update_status(status, client->ops.cb_arg);
-	talloc_free(status);
 }
 
 static void update_sysinfo(struct discover_client *client,
@@ -123,7 +122,6 @@ static void update_sysinfo(struct discover_client *client,
 {
 	if (client->ops.update_sysinfo)
 		client->ops.update_sysinfo(sysinfo, client->ops.cb_arg);
-	talloc_free(sysinfo);
 }
 
 static void update_config(struct discover_client *client,
@@ -143,16 +141,21 @@ static int discover_client_process(void *arg)
 	struct config *config;
 	struct device *dev;
 	char *dev_id;
+	void *ctx;
 	int rc;
 
-	message = pb_protocol_read_message(client, client->fd);
+	/* We use a temporary context for processing one message; persistent
+	 * data is re-parented to the client in the callbacks. */
+	ctx = talloc_new(client);
+
+	message = pb_protocol_read_message(ctx, client->fd);
 
 	if (!message)
 		return -1;
 
 	switch (message->action) {
 	case PB_PROTOCOL_ACTION_DEVICE_ADD:
-		dev = talloc_zero(client, struct device);
+		dev = talloc_zero(ctx, struct device);
 		list_init(&dev->boot_options);
 
 		rc = pb_protocol_deserialise_device(dev, message);
@@ -164,7 +167,7 @@ static int discover_client_process(void *arg)
 		device_add(client, dev);
 		break;
 	case PB_PROTOCOL_ACTION_BOOT_OPTION_ADD:
-		opt = talloc_zero(client, struct boot_option);
+		opt = talloc_zero(ctx, struct boot_option);
 
 		rc = pb_protocol_deserialise_boot_option(opt, message);
 		if (rc) {
@@ -175,7 +178,7 @@ static int discover_client_process(void *arg)
 		boot_option_add(client, opt);
 		break;
 	case PB_PROTOCOL_ACTION_DEVICE_REMOVE:
-		dev_id = pb_protocol_deserialise_string(client, message);
+		dev_id = pb_protocol_deserialise_string(ctx, message);
 		if (!dev_id) {
 			pb_log("%s: no device id?\n", __func__);
 			return 0;
@@ -183,7 +186,7 @@ static int discover_client_process(void *arg)
 		device_remove(client, dev_id);
 		break;
 	case PB_PROTOCOL_ACTION_STATUS:
-		status = talloc_zero(client, struct boot_status);
+		status = talloc_zero(ctx, struct boot_status);
 
 		rc = pb_protocol_deserialise_boot_status(status, message);
 		if (rc) {
@@ -193,7 +196,7 @@ static int discover_client_process(void *arg)
 		update_status(client, status);
 		break;
 	case PB_PROTOCOL_ACTION_SYSTEM_INFO:
-		sysinfo = talloc_zero(client, struct system_info);
+		sysinfo = talloc_zero(ctx, struct system_info);
 
 		rc = pb_protocol_deserialise_system_info(sysinfo, message);
 		if (rc) {
@@ -216,6 +219,7 @@ static int discover_client_process(void *arg)
 		pb_log("%s: unknown action %d\n", __func__, message->action);
 	}
 
+	talloc_free(ctx);
 
 	return 0;
 }
diff --git a/ui/common/discover-client.h b/ui/common/discover-client.h
index 6aa0432..fa97fa5 100644
--- a/ui/common/discover-client.h
+++ b/ui/common/discover-client.h
@@ -18,6 +18,15 @@ struct pb_boot_data {
  * @device_add: PB_PROTOCOL_ACTION_ADD event callback.
  * @device_remove: PB_PROTOCOL_ACTION_REMOVE event callback.
  * @cb_arg: Client managed convenience variable passed to callbacks.
+ *
+ * The discover client holds talloc references to the devices (and the
+ * devices' boot options), so callbacks may store boot options and devices
+ * as long as the client remains allocated.
+ *
+ * The boot_status and system_info structs are allocated by the client,
+ * and will be free()ed after the callback is invoked. If the callback
+ * stores these structures for usage beyond the duration of the callback,
+ * it must talloc_steal() them.
  */
 
 struct discover_client_ops {