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camerabin2: Add a mutex to avoid concurrent access of preview filename lists

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The preview filename list is acessed whenever a new capture is started, when
camera-source posts a new preview message or on state changes. All of those can
occur simultaneously, so add a mutex to prevent concurrent access.
This commit is contained in:
Thiago Santos 2011-10-11 23:13:00 -03:00
parent 17a00123a4
commit e90e041e52
2 changed files with 23 additions and 1 deletions
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8
gst/camerabin2/gstcamerabin2.c
View file

@ -406,8 +406,10 @@ gst_camera_bin_start_capture (GstCameraBin2 * camerabin)
}
/* store the next preview filename */
g_mutex_lock (camerabin->preview_list_mutex);
camerabin->preview_location_list =
g_slist_append (camerabin->preview_location_list, location);
g_mutex_unlock (camerabin->preview_list_mutex);
g_signal_emit_by_name (camerabin->src, "start-capture", NULL);
if (camerabin->mode == MODE_VIDEO && camerabin->audio_src)
@ -518,6 +520,7 @@ gst_camera_bin_dispose (GObject * object)
GstCameraBin2 *camerabin = GST_CAMERA_BIN2_CAST (object);
g_free (camerabin->location);
g_mutex_free (camerabin->preview_list_mutex);
if (camerabin->src_capture_notify_id)
g_signal_handler_disconnect (camerabin->src,
@ -873,6 +876,7 @@ gst_camera_bin_init (GstCameraBin2 * camera)
camera->zoom = DEFAULT_ZOOM;
camera->max_zoom = MAX_ZOOM;
camera->flags = DEFAULT_FLAGS;
camera->preview_list_mutex = g_mutex_new ();
/* capsfilters are created here as we proxy their caps properties and
* this way we avoid having to store the caps while on NULL state to
@ -947,12 +951,14 @@ gst_camera_bin_handle_message (GstBin * bin, GstMessage * message)
GValue *value;
gchar *location;
g_mutex_lock (camerabin->preview_list_mutex);
location = camerabin->preview_location_list->data;
camerabin->preview_location_list =
g_slist_delete_link (camerabin->preview_location_list,
camerabin->preview_location_list);
GST_DEBUG_OBJECT (camerabin, "Adding preview location to preview "
"message '%s'", location);
g_mutex_unlock (camerabin->preview_list_mutex);
value = g_new0 (GValue, 1);
g_value_init (value, G_TYPE_STRING);
@ -1725,9 +1731,11 @@ gst_camera_bin_change_state (GstElement * element, GstStateChange trans)
g_slist_free (camera->image_location_list);
camera->image_location_list = NULL;
g_mutex_lock (camera->preview_list_mutex);
g_slist_foreach (camera->preview_location_list, (GFunc) g_free, NULL);
g_slist_free (camera->preview_location_list);
camera->preview_location_list = NULL;
g_mutex_unlock (camera->preview_list_mutex);
/* explicitly set to READY as they might be outside of the bin */
gst_element_set_state (camera->audio_volume, GST_STATE_READY);

16
gst/camerabin2/gstcamerabin2.h
View file

@ -94,8 +94,22 @@ struct _GstCameraBin2
* each buffer capture */
GSList *image_location_list;
/* similar to above, but used for giving names to previews */
/*
* Similar to above, but used for giving names to previews
*
* Need to protect with a mutex as this list is used when the
* camera-source posts a preview image. As we have no control
* on how the camera-source will behave (we can only tell how
* it should), the preview location list might be used in an
* inconsistent way.
* One example is the camera-source posting a preview image after
* camerabin2 was put to ready, when this preview list will be
* freed and set to NULL. Concurrent access might lead to crashes in
* this situation. (Concurrency from the state-change freeing the
* list and the message handling function looking at preview names)
*/
GSList *preview_location_list;
GMutex *preview_list_mutex;
gboolean video_profile_switch;
gboolean image_profile_switch;