v4l2: Fix SIGSEGV on 'change state' during 'format change'

Ensure all access to v4l2object->pool imply taking a lock and a hard ref on the pool

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3481>

subprojects/gst-plugins-good/sys/v4l2/gstv4l2bufferpool.c

@@ -1024,21 +1024,25 @@ gst_v4l2_buffer_pool_stop (GstBufferPool * bpool)
 }
 
 gboolean
-gst_v4l2_buffer_pool_orphan (GstBufferPool ** bpool)
+gst_v4l2_buffer_pool_orphan (GstV4l2Object * v4l2object)
 {
-  GstV4l2BufferPool *pool = GST_V4L2_BUFFER_POOL (*bpool);
+  GstBufferPool *bpool = gst_v4l2_object_get_buffer_pool (v4l2object);
+  GstV4l2BufferPool *pool;
   gboolean ret;
 
-  g_return_val_if_fail (pool->orphaned == FALSE, FALSE);
+  g_return_val_if_fail (bpool, FALSE);
 
-  if (!GST_V4L2_ALLOCATOR_CAN_ORPHAN_BUFS (pool->vallocator))
+  pool = GST_V4L2_BUFFER_POOL (bpool);
-    return FALSE;
 
-  if (g_getenv ("GST_V4L2_FORCE_DRAIN"))
+  if (pool->orphaned != FALSE
+      || !GST_V4L2_ALLOCATOR_CAN_ORPHAN_BUFS (pool->vallocator)
+      || g_getenv ("GST_V4L2_FORCE_DRAIN")) {
+    gst_object_unref (bpool);
     return FALSE;
+  }
 
   GST_DEBUG_OBJECT (pool, "orphaning pool");
-  gst_buffer_pool_set_active (*bpool, FALSE);
+  gst_buffer_pool_set_active (bpool, FALSE);
 
   /* We lock to prevent racing with a return buffer in QBuf, and has a
    * workaround of not being able to use the pool hidden activation lock. */
@@ -1052,10 +1056,17 @@ gst_v4l2_buffer_pool_orphan (GstBufferPool ** bpool)
   GST_OBJECT_UNLOCK (pool);
 
   if (ret) {
-    gst_object_unref (*bpool);
+    GstBufferPool *old_pool;
-    *bpool = NULL;
+    GST_OBJECT_LOCK (v4l2object->element);
+    old_pool = v4l2object->pool;
+    v4l2object->pool = NULL;
+    GST_OBJECT_UNLOCK (v4l2object->element);
+    if (old_pool)
+      gst_object_unref (old_pool);
   }
 
+  gst_object_unref (bpool);
+
   return ret;
 }
 
@@ -2288,16 +2299,23 @@ gst_v4l2_buffer_pool_copy_at_threshold (GstV4l2BufferPool * pool, gboolean copy)
 }
 
 gboolean
-gst_v4l2_buffer_pool_flush (GstBufferPool * bpool)
+gst_v4l2_buffer_pool_flush (GstV4l2Object * v4l2object)
 {
-  GstV4l2BufferPool *pool = GST_V4L2_BUFFER_POOL (bpool);
+  GstBufferPool *bpool = gst_v4l2_object_get_buffer_pool (v4l2object);
+  GstV4l2BufferPool *pool;
   gboolean ret = TRUE;
 
+  if (!bpool)
+    return FALSE;
+
+  pool = GST_V4L2_BUFFER_POOL (bpool);
+
   gst_v4l2_buffer_pool_streamoff (pool);
 
   if (!V4L2_TYPE_IS_OUTPUT (pool->obj->type))
     ret = gst_v4l2_buffer_pool_streamon (pool);
 
+  gst_object_unref (bpool);
   return ret;
 }
 

subprojects/gst-plugins-good/sys/v4l2/gstv4l2bufferpool.h

@@ -118,9 +118,9 @@ void                gst_v4l2_buffer_pool_set_other_pool (GstV4l2BufferPool * poo
 void                gst_v4l2_buffer_pool_copy_at_threshold (GstV4l2BufferPool * pool,
                                                             gboolean copy);
 
-gboolean            gst_v4l2_buffer_pool_flush   (GstBufferPool *pool);
+gboolean            gst_v4l2_buffer_pool_flush   (GstV4l2Object * v4l2object);
 
-gboolean            gst_v4l2_buffer_pool_orphan  (GstBufferPool ** pool);
+gboolean            gst_v4l2_buffer_pool_orphan  (GstV4l2Object * v4l2object);
 
 void                gst_v4l2_buffer_pool_enable_resolution_change (GstV4l2BufferPool *self);
 

subprojects/gst-plugins-good/sys/v4l2/gstv4l2object.c

@@ -3172,8 +3172,14 @@ gst_v4l2_object_setup_pool (GstV4l2Object * v4l2object, GstCaps * caps)
   /* Map the buffers */
   GST_LOG_OBJECT (v4l2object->dbg_obj, "initiating buffer pool");
 
-  if (!(v4l2object->pool = gst_v4l2_buffer_pool_new (v4l2object, caps)))
+  {
+    GstBufferPool *pool = gst_v4l2_buffer_pool_new (v4l2object, caps);
+    GST_OBJECT_LOCK (v4l2object->element);
+    v4l2object->pool = pool;
+    GST_OBJECT_UNLOCK (v4l2object->element);
+    if (!pool)
       goto buffer_pool_new_failed;
+  }
 
   GST_V4L2_SET_ACTIVE (v4l2object);
 
@@ -4515,17 +4521,19 @@ gst_v4l2_object_caps_equal (GstV4l2Object * v4l2object, GstCaps * caps)
   GstStructure *config;
   GstCaps *oldcaps;
   gboolean ret;
+  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (v4l2object);
 
-  if (!v4l2object->pool)
+  if (!pool)
     return FALSE;
 
-  config = gst_buffer_pool_get_config (v4l2object->pool);
+  config = gst_buffer_pool_get_config (pool);
   gst_buffer_pool_config_get_params (config, &oldcaps, NULL, NULL, NULL);
 
   ret = oldcaps && gst_caps_is_equal (caps, oldcaps);
 
   gst_structure_free (config);
 
+  gst_object_unref (pool);
   return ret;
 }
 
@@ -4535,17 +4543,19 @@ gst_v4l2_object_caps_is_subset (GstV4l2Object * v4l2object, GstCaps * caps)
   GstStructure *config;
   GstCaps *oldcaps;
   gboolean ret;
+  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (v4l2object);
 
-  if (!v4l2object->pool)
+  if (!pool)
     return FALSE;
 
-  config = gst_buffer_pool_get_config (v4l2object->pool);
+  config = gst_buffer_pool_get_config (pool);
   gst_buffer_pool_config_get_params (config, &oldcaps, NULL, NULL, NULL);
 
   ret = oldcaps && gst_caps_is_subset (oldcaps, caps);
 
   gst_structure_free (config);
 
+  gst_object_unref (pool);
   return ret;
 }
 
@@ -4554,11 +4564,12 @@ gst_v4l2_object_get_current_caps (GstV4l2Object * v4l2object)
 {
   GstStructure *config;
   GstCaps *oldcaps;
+  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (v4l2object);
 
-  if (!v4l2object->pool)
+  if (!pool)
     return NULL;
 
-  config = gst_buffer_pool_get_config (v4l2object->pool);
+  config = gst_buffer_pool_get_config (pool);
   gst_buffer_pool_config_get_params (config, &oldcaps, NULL, NULL, NULL);
 
   if (oldcaps)
@@ -4566,6 +4577,7 @@ gst_v4l2_object_get_current_caps (GstV4l2Object * v4l2object)
 
   gst_structure_free (config);
 
+  gst_object_unref (pool);
   return oldcaps;
 }
 
@@ -4573,12 +4585,17 @@ gboolean
 gst_v4l2_object_unlock (GstV4l2Object * v4l2object)
 {
   gboolean ret = TRUE;
+  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (v4l2object);
 
   GST_LOG_OBJECT (v4l2object->dbg_obj, "start flushing");
 
-  if (v4l2object->pool && gst_buffer_pool_is_active (v4l2object->pool))
+  if (!pool)
-    gst_buffer_pool_set_flushing (v4l2object->pool, TRUE);
+    return ret;
 
+  if (gst_buffer_pool_is_active (pool))
+    gst_buffer_pool_set_flushing (pool, TRUE);
+
+  gst_object_unref (pool);
   return ret;
 }
 
@@ -4586,18 +4603,24 @@ gboolean
 gst_v4l2_object_unlock_stop (GstV4l2Object * v4l2object)
 {
   gboolean ret = TRUE;
+  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (v4l2object);
 
   GST_LOG_OBJECT (v4l2object->dbg_obj, "stop flushing");
 
-  if (v4l2object->pool && gst_buffer_pool_is_active (v4l2object->pool))
+  if (!pool)
-    gst_buffer_pool_set_flushing (v4l2object->pool, FALSE);
+    return ret;
 
+  if (gst_buffer_pool_is_active (pool))
+    gst_buffer_pool_set_flushing (pool, FALSE);
+
+  gst_object_unref (pool);
   return ret;
 }
 
 gboolean
 gst_v4l2_object_stop (GstV4l2Object * v4l2object)
 {
+  GstBufferPool *pool;
   GST_DEBUG_OBJECT (v4l2object->dbg_obj, "stopping");
 
   if (!GST_V4L2_IS_OPEN (v4l2object))
@@ -4605,13 +4628,23 @@ gst_v4l2_object_stop (GstV4l2Object * v4l2object)
   if (!GST_V4L2_IS_ACTIVE (v4l2object))
     goto done;
 
-  if (v4l2object->pool) {
+  pool = gst_v4l2_object_get_buffer_pool (v4l2object);
-    if (!gst_v4l2_buffer_pool_orphan (&v4l2object->pool)) {
+  if (pool) {
+    if (!gst_v4l2_buffer_pool_orphan (v4l2object)) {
       GST_DEBUG_OBJECT (v4l2object->dbg_obj, "deactivating pool");
-      gst_buffer_pool_set_active (v4l2object->pool, FALSE);
+      gst_buffer_pool_set_active (pool, FALSE);
-      gst_object_unref (v4l2object->pool);
+
-    }
+      {
+        GstBufferPool *old_pool;
+        GST_OBJECT_LOCK (v4l2object->element);
+        old_pool = v4l2object->pool;
         v4l2object->pool = NULL;
+        GST_OBJECT_UNLOCK (v4l2object->element);
+        if (old_pool)
+          gst_object_unref (old_pool);
+      }
+      gst_object_unref (pool);
+    }
   }
 
   GST_V4L2_SET_INACTIVE (v4l2object);
@@ -4958,7 +4991,7 @@ gboolean
 gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
 {
   GstCaps *caps;
-  GstBufferPool *pool = NULL, *other_pool = NULL;
+  GstBufferPool *pool = NULL, *other_pool = NULL, *obj_pool = NULL;
   GstStructure *config;
   guint size, min, max, own_min = 0;
   gboolean update;
@@ -4975,9 +5008,13 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
 
   gst_query_parse_allocation (query, &caps, NULL);
 
-  if (obj->pool == NULL) {
+  obj_pool = gst_v4l2_object_get_buffer_pool (obj);
+  if (obj_pool == NULL) {
     if (!gst_v4l2_object_setup_pool (obj, caps))
       goto pool_failed;
+    obj_pool = gst_v4l2_object_get_buffer_pool (obj);
+    if (obj_pool == NULL)
+      goto pool_failed;
   }
 
   if (gst_query_get_n_allocation_params (query) > 0)
@@ -5031,7 +5068,7 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
         /* no downstream pool, use our own then */
         GST_DEBUG_OBJECT (obj->dbg_obj,
             "read/write mode: no downstream pool, using our own");
-        pool = gst_object_ref (obj->pool);
+        pool = gst_object_ref (obj_pool);
         size = obj->info.size;
         pushing_from_our_pool = TRUE;
       }
@@ -5043,11 +5080,11 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
        * our own, so it can serve itself */
       if (pool == NULL)
         goto no_downstream_pool;
-      gst_v4l2_buffer_pool_set_other_pool (GST_V4L2_BUFFER_POOL (obj->pool),
+      gst_v4l2_buffer_pool_set_other_pool (GST_V4L2_BUFFER_POOL (obj_pool),
           pool);
       other_pool = pool;
       gst_object_unref (pool);
-      pool = gst_object_ref (obj->pool);
+      pool = gst_object_ref (obj_pool);
       size = obj->info.size;
       break;
 
@@ -5058,7 +5095,7 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
       if (can_share_own_pool) {
         if (pool)
           gst_object_unref (pool);
-        pool = gst_object_ref (obj->pool);
+        pool = gst_object_ref (obj_pool);
         size = obj->info.size;
         GST_DEBUG_OBJECT (obj->dbg_obj,
             "streaming mode: using our own pool %" GST_PTR_FORMAT, pool);
@@ -5116,7 +5153,7 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
     min = MAX (min, GST_V4L2_MIN_BUFFERS (obj));
 
     /* To import we need the other pool to hold at least own_min */
-    if (obj->pool == pool)
+    if (obj_pool == pool)
       min += own_min;
   }
 
@@ -5125,7 +5162,7 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
     max = MAX (min, max);
 
   /* First step, configure our own pool */
-  config = gst_buffer_pool_get_config (obj->pool);
+  config = gst_buffer_pool_get_config (obj_pool);
 
   if (obj->need_video_meta || has_video_meta) {
     GST_DEBUG_OBJECT (obj->dbg_obj, "activate Video Meta");
@@ -5140,19 +5177,19 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
       GST_PTR_FORMAT, config);
 
   /* Our pool often need to adjust the value */
-  if (!gst_buffer_pool_set_config (obj->pool, config)) {
+  if (!gst_buffer_pool_set_config (obj_pool, config)) {
-    config = gst_buffer_pool_get_config (obj->pool);
+    config = gst_buffer_pool_get_config (obj_pool);
 
     GST_DEBUG_OBJECT (obj->dbg_obj, "own pool config changed to %"
         GST_PTR_FORMAT, config);
 
     /* our pool will adjust the maximum buffer, which we are fine with */
-    if (!gst_buffer_pool_set_config (obj->pool, config))
+    if (!gst_buffer_pool_set_config (obj_pool, config))
       goto config_failed;
   }
 
   /* Now configure the other pool if different */
-  if (obj->pool != pool)
+  if (obj_pool != pool)
     other_pool = pool;
 
   if (other_pool) {
@@ -5203,6 +5240,9 @@ gst_v4l2_object_decide_allocation (GstV4l2Object * obj, GstQuery * query)
   if (pool)
     gst_object_unref (pool);
 
+  if (obj_pool)
+    gst_object_unref (obj_pool);
+
   return TRUE;
 
 pool_failed:
@@ -5222,6 +5262,13 @@ no_size:
         (_("Video device did not suggest any buffer size.")), (NULL));
     goto cleanup;
   }
+no_downstream_pool:
+  {
+    GST_ELEMENT_ERROR (obj->element, RESOURCE, SETTINGS,
+        (_("No downstream pool to import from.")),
+        ("When importing DMABUF or USERPTR, we need a pool to import from"));
+    goto cleanup;
+  }
 cleanup:
   {
     if (allocator)
@@ -5229,13 +5276,9 @@ cleanup:
 
     if (pool)
       gst_object_unref (pool);
-    return FALSE;
+
-  }
+    if (obj_pool)
-no_downstream_pool:
+      gst_object_unref (obj_pool);
-  {
-    GST_ELEMENT_ERROR (obj->element, RESOURCE, SETTINGS,
-        (_("No downstream pool to import from.")),
-        ("When importing DMABUF or USERPTR, we need a pool to import from"));
     return FALSE;
   }
 }
@@ -5262,9 +5305,14 @@ gst_v4l2_object_propose_allocation (GstV4l2Object * obj, GstQuery * query)
   switch (obj->mode) {
     case GST_V4L2_IO_MMAP:
     case GST_V4L2_IO_DMABUF:
-      if (need_pool && obj->pool) {
+      if (need_pool) {
-        if (!gst_buffer_pool_is_active (obj->pool))
+        GstBufferPool *obj_pool = gst_v4l2_object_get_buffer_pool (obj);
-          pool = gst_object_ref (obj->pool);
+        if (obj_pool) {
+          if (!gst_buffer_pool_is_active (obj_pool))
+            pool = gst_object_ref (obj_pool);
+
+          gst_object_unref (obj_pool);
+        }
       }
       break;
     default:
@@ -5377,3 +5425,25 @@ gst_v4l2_object_try_import (GstV4l2Object * obj, GstBuffer * buffer)
   /* for the remaining, only the kernel driver can tell */
   return TRUE;
 }
+
+/**
+ * gst_v4l2_object_get_buffer_pool:
+ * @src: a #GstV4l2Object
+ *
+ * Returns: (nullable) (transfer full): the instance of the #GstBufferPool used
+ * by the v4l2object; unref it after usage.
+ */
+GstBufferPool *
+gst_v4l2_object_get_buffer_pool (GstV4l2Object * v4l2object)
+{
+  GstBufferPool *ret = NULL;
+
+  g_return_val_if_fail (v4l2object != NULL, NULL);
+
+  GST_OBJECT_LOCK (v4l2object->element);
+  if (v4l2object->pool)
+    ret = gst_object_ref (v4l2object->pool);
+  GST_OBJECT_UNLOCK (v4l2object->element);
+
+  return ret;
+}

subprojects/gst-plugins-good/sys/v4l2/gstv4l2object.h

@@ -311,6 +311,8 @@ gboolean     gst_v4l2_object_decide_allocation (GstV4l2Object * v4l2object, GstQ
 
 gboolean     gst_v4l2_object_propose_allocation (GstV4l2Object * obj, GstQuery * query);
 
+GstBufferPool * gst_v4l2_object_get_buffer_pool (GstV4l2Object * v4l2object);
+
 GstStructure * gst_v4l2_object_v4l2fourcc_to_structure (guint32 fourcc);
 
 /* crop / compose */

subprojects/gst-plugins-good/sys/v4l2/gstv4l2sink.c

@@ -587,11 +587,11 @@ gst_v4l2sink_show_frame (GstVideoSink * vsink, GstBuffer * buf)
   GstFlowReturn ret;
   GstV4l2Sink *v4l2sink = GST_V4L2SINK (vsink);
   GstV4l2Object *obj = v4l2sink->v4l2object;
-  GstBufferPool *bpool = GST_BUFFER_POOL (obj->pool);
+  GstBufferPool *bpool = gst_v4l2_object_get_buffer_pool (obj);
 
   GST_DEBUG_OBJECT (v4l2sink, "render buffer: %p", buf);
 
-  if (G_UNLIKELY (obj->pool == NULL))
+  if (G_UNLIKELY (bpool == NULL))
     goto not_negotiated;
 
   if (G_UNLIKELY (!gst_buffer_pool_is_active (bpool))) {
@@ -611,7 +611,7 @@ gst_v4l2sink_show_frame (GstVideoSink * vsink, GstBuffer * buf)
 
   gst_buffer_ref (buf);
 again:
-  ret = gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL_CAST (obj->pool),
+  ret = gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL_CAST (bpool),
       &buf, NULL);
   if (ret == GST_FLOW_FLUSHING) {
     ret = gst_base_sink_wait_preroll (GST_BASE_SINK (vsink));
@@ -619,6 +619,8 @@ again:
       goto again;
   }
   gst_buffer_unref (buf);
+  if (bpool)
+    gst_object_unref (bpool);
 
   return ret;
 
@@ -633,6 +635,8 @@ activate_failed:
     GST_ELEMENT_ERROR (v4l2sink, RESOURCE, SETTINGS,
         (_("Failed to allocated required memory.")),
         ("Buffer pool activation failed"));
+    if (bpool)
+      gst_object_unref (bpool);
     return GST_FLOW_ERROR;
   }
 }

subprojects/gst-plugins-good/sys/v4l2/gstv4l2src.c

@@ -647,6 +647,7 @@ gst_v4l2src_query_preferred_dv_timings (GstV4l2Src * v4l2src,
   GstV4l2Object *obj = v4l2src->v4l2object;
   struct v4l2_dv_timings dv_timings = { 0, };
   const struct v4l2_bt_timings *bt = &dv_timings.bt;
+  gboolean not_streaming;
   gint tot_width, tot_height;
   gint gcd;
 
@@ -673,7 +674,14 @@ gst_v4l2src_query_preferred_dv_timings (GstV4l2Src * v4l2src,
 
   /* If are are not streaming (e.g. we received source-change event), lock the
    * new timing immediatly so that TRY_FMT can properly work */
-  if (!obj->pool || !GST_V4L2_BUFFER_POOL_IS_STREAMING (obj->pool)) {
+  {
+    GstBufferPool *obj_pool = gst_v4l2_object_get_buffer_pool (obj);
+    not_streaming = !obj_pool || !GST_V4L2_BUFFER_POOL_IS_STREAMING (obj_pool);
+    if (obj_pool)
+      gst_object_unref (obj_pool);
+  }
+
+  if (not_streaming) {
     gst_v4l2_set_dv_timings (obj, &dv_timings);
     /* Setting a new DV timings invalidates the probed caps. */
     gst_caps_replace (&obj->probed_caps, NULL);
@@ -892,6 +900,7 @@ static gboolean
 gst_v4l2src_decide_allocation (GstBaseSrc * bsrc, GstQuery * query)
 {
   GstV4l2Src *src = GST_V4L2SRC (bsrc);
+  GstBufferPool *bpool = gst_v4l2_object_get_buffer_pool (src->v4l2object);
   gboolean ret = TRUE;
 
   if (src->pending_set_fmt) {
@@ -902,7 +911,7 @@ gst_v4l2src_decide_allocation (GstBaseSrc * bsrc, GstQuery * query)
 
     ret = gst_v4l2src_set_format (src, caps, &error);
     if (ret) {
-      GstV4l2BufferPool *pool = GST_V4L2_BUFFER_POOL (src->v4l2object->pool);
+      GstV4l2BufferPool *pool = GST_V4L2_BUFFER_POOL (bpool);
       gst_v4l2_buffer_pool_enable_resolution_change (pool);
     } else {
       gst_v4l2_error (src, &error);
@@ -910,7 +919,7 @@ gst_v4l2src_decide_allocation (GstBaseSrc * bsrc, GstQuery * query)
 
     gst_caps_unref (caps);
     src->pending_set_fmt = FALSE;
-  } else if (gst_buffer_pool_is_active (src->v4l2object->pool)) {
+  } else if (gst_buffer_pool_is_active (bpool)) {
     /* Trick basesrc into not deactivating the active pool. Renegotiating here
      * would otherwise turn off and on the camera. */
     GstAllocator *allocator;
@@ -936,6 +945,8 @@ gst_v4l2src_decide_allocation (GstBaseSrc * bsrc, GstQuery * query)
       gst_object_unref (pool);
     if (allocator)
       gst_object_unref (allocator);
+    if (bpool)
+      gst_object_unref (bpool);
 
     return GST_BASE_SRC_CLASS (parent_class)->decide_allocation (bsrc, query);
   }
@@ -947,10 +958,12 @@ gst_v4l2src_decide_allocation (GstBaseSrc * bsrc, GstQuery * query)
   }
 
   if (ret) {
-    if (!gst_buffer_pool_set_active (src->v4l2object->pool, TRUE))
+    if (!gst_buffer_pool_set_active (bpool, TRUE))
       goto activate_failed;
   }
 
+  if (bpool)
+    gst_object_unref (bpool);
   return ret;
 
 activate_failed:
@@ -958,6 +971,8 @@ activate_failed:
     GST_ELEMENT_ERROR (src, RESOURCE, SETTINGS,
         (_("Failed to allocate required memory.")),
         ("Buffer pool activation failed"));
+    if (bpool)
+      gst_object_unref (bpool);
     return FALSE;
   }
 }
@@ -1002,8 +1017,13 @@ gst_v4l2src_query (GstBaseSrc * bsrc, GstQuery * query)
         min_latency /= 2;
 
       /* max latency is total duration of the frame buffer */
-      if (obj->pool != NULL)
+      {
-        num_buffers = GST_V4L2_BUFFER_POOL_CAST (obj->pool)->max_latency;
+        GstBufferPool *obj_pool = gst_v4l2_object_get_buffer_pool (obj);
+        if (obj_pool != NULL) {
+          num_buffers = GST_V4L2_BUFFER_POOL_CAST (obj_pool)->max_latency;
+          gst_object_unref (obj_pool);
+        }
+      }
 
       if (num_buffers == 0)
         max_latency = -1;
@@ -1136,8 +1156,6 @@ gst_v4l2src_create (GstPushSrc * src, GstBuffer ** buf)
   gboolean half_frame;
 
   do {
-    GstV4l2BufferPool *pool = GST_V4L2_BUFFER_POOL_CAST (obj->pool);
-
     ret = GST_BASE_SRC_CLASS (parent_class)->alloc (GST_BASE_SRC (src), 0,
         obj->info.size, buf);
 
@@ -1164,7 +1182,13 @@ gst_v4l2src_create (GstPushSrc * src, GstBuffer ** buf)
       goto alloc_failed;
     }
 
-    ret = gst_v4l2_buffer_pool_process (pool, buf, NULL);
+    {
+      GstV4l2BufferPool *obj_pool =
+          GST_V4L2_BUFFER_POOL_CAST (gst_v4l2_object_get_buffer_pool (obj));
+      ret = gst_v4l2_buffer_pool_process (obj_pool, buf, NULL);
+      if (obj_pool)
+        gst_object_unref (obj_pool);
+    }
 
   } while (ret == GST_V4L2_FLOW_CORRUPTED_BUFFER ||
       ret == GST_V4L2_FLOW_RESOLUTION_CHANGE);

subprojects/gst-plugins-good/sys/v4l2/gstv4l2transform.c

@@ -318,12 +318,16 @@ gst_v4l2_transform_decide_allocation (GstBaseTransform * trans,
   GST_DEBUG_OBJECT (self, "called");
 
   if (gst_v4l2_object_decide_allocation (self->v4l2capture, query)) {
-    GstBufferPool *pool = GST_BUFFER_POOL (self->v4l2capture->pool);
+    gboolean pool_active;
+    GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (self->v4l2capture);
 
     ret = GST_BASE_TRANSFORM_CLASS (parent_class)->decide_allocation (trans,
         query);
 
-    if (!gst_buffer_pool_set_active (pool, TRUE))
+    pool_active = gst_buffer_pool_set_active (pool, TRUE);
+    if (pool)
+      gst_object_unref (pool);
+    if (!pool_active)
       goto activate_failed;
   }
 
@@ -883,7 +887,7 @@ gst_v4l2_transform_prepare_output_buffer (GstBaseTransform * trans,
     GstBuffer * inbuf, GstBuffer ** outbuf)
 {
   GstV4l2Transform *self = GST_V4L2_TRANSFORM (trans);
-  GstBufferPool *pool = GST_BUFFER_POOL (self->v4l2output->pool);
+  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
   GstFlowReturn ret = GST_FLOW_OK;
   GstBaseTransformClass *bclass = GST_BASE_TRANSFORM_CLASS (parent_class);
 
@@ -932,6 +936,8 @@ gst_v4l2_transform_prepare_output_buffer (GstBaseTransform * trans,
     goto beach;
 
   do {
+    if (pool)
+      g_object_unref (pool);
     pool = gst_base_transform_get_buffer_pool (trans);
 
     if (!gst_buffer_pool_set_active (pool, TRUE))
@@ -944,7 +950,7 @@ gst_v4l2_transform_prepare_output_buffer (GstBaseTransform * trans,
     if (ret != GST_FLOW_OK)
       goto alloc_failed;
 
-    pool = self->v4l2capture->pool;
+    pool = gst_v4l2_object_get_buffer_pool (self->v4l2capture);
     ret =
         gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (pool), outbuf,
         NULL);
@@ -964,6 +970,8 @@ gst_v4l2_transform_prepare_output_buffer (GstBaseTransform * trans,
     }
 
 beach:
+  if (pool)
+    g_object_unref (pool);
   return ret;
 
 activate_failed:
@@ -1014,10 +1022,8 @@ gst_v4l2_transform_sink_event (GstBaseTransform * trans, GstEvent * event)
       GST_DEBUG_OBJECT (self, "flush stop");
       gst_v4l2_object_unlock_stop (self->v4l2capture);
       gst_v4l2_object_unlock_stop (self->v4l2output);
-      if (self->v4l2output->pool)
+      gst_v4l2_buffer_pool_flush (self->v4l2output);
-        gst_v4l2_buffer_pool_flush (self->v4l2output->pool);
+      gst_v4l2_buffer_pool_flush (self->v4l2capture);
-      if (self->v4l2capture->pool)
-        gst_v4l2_buffer_pool_flush (self->v4l2capture->pool);
       break;
     default:
       break;

subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.c

@@ -286,8 +286,7 @@ gst_v4l2_video_dec_set_format (GstVideoDecoder * decoder,
      * the complexity and should not have much impact in performance since the
      * following allocation query will happen on a drained pipeline and won't
      * block. */
-    if (self->v4l2capture->pool &&
+    if (!gst_v4l2_buffer_pool_orphan (self->v4l2capture)) {
-        !gst_v4l2_buffer_pool_orphan (&self->v4l2capture->pool)) {
       GstCaps *caps = gst_pad_get_current_caps (decoder->srcpad);
       if (caps) {
         GstQuery *query = gst_query_new_allocation (caps, FALSE);
@@ -351,14 +350,12 @@ gst_v4l2_video_dec_flush (GstVideoDecoder * decoder)
   gst_v4l2_object_unlock_stop (self->v4l2output);
   gst_v4l2_object_unlock_stop (self->v4l2capture);
 
-  if (self->v4l2output->pool)
+  gst_v4l2_buffer_pool_flush (self->v4l2output);
-    gst_v4l2_buffer_pool_flush (self->v4l2output->pool);
 
   /* gst_v4l2_buffer_pool_flush() calls streamon the capture pool and must be
    * called after gst_v4l2_object_unlock_stop() stopped flushing the buffer
    * pool. */
-  if (self->v4l2capture->pool)
+  gst_v4l2_buffer_pool_flush (self->v4l2capture);
-    gst_v4l2_buffer_pool_flush (self->v4l2capture->pool);
 
   return TRUE;
 }
@@ -369,9 +366,15 @@ gst_v4l2_video_dec_negotiate (GstVideoDecoder * decoder)
   GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
 
   /* We don't allow renegotiation without careful disabling the pool */
-  if (self->v4l2capture->pool &&
+  {
-      gst_buffer_pool_is_active (GST_BUFFER_POOL (self->v4l2capture->pool)))
+    GstBufferPool *cpool = gst_v4l2_object_get_buffer_pool (self->v4l2capture);
+    if (cpool) {
+      gboolean is_active = gst_buffer_pool_is_active (cpool);
+      gst_object_unref (cpool);
+      if (is_active)
         return TRUE;
+    }
+  }
 
   return GST_VIDEO_DECODER_CLASS (parent_class)->negotiate (decoder);
 }
@@ -444,15 +447,18 @@ gst_v4l2_video_dec_finish (GstVideoDecoder * decoder)
       gst_object_unref (task);
     }
   } else {
+    GstBufferPool *opool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
     /* otherwise keep queuing empty buffers until the processing thread has
      * stopped, _pool_process() will return FLUSHING when that happened */
     while (ret == GST_FLOW_OK) {
       buffer = gst_buffer_new ();
       ret =
-          gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->
+          gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (opool), &buffer,
-              v4l2output->pool), &buffer, NULL);
+          NULL);
       gst_buffer_unref (buffer);
     }
+    if (opool)
+      gst_object_unref (opool);
   }
 
   /* and ensure the processing thread has stopped in case another error
@@ -566,6 +572,8 @@ gst_v4l2_video_dec_setup_capture (GstVideoDecoder * decoder)
   GstVideoCodecState *output_state;
   GstCaps *acquired_caps, *available_caps, *caps, *filter;
   GstStructure *st;
+  GstBufferPool *cpool;
+  gboolean active;
 
   if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2capture))) {
     /* init capture fps according to output */
@@ -635,10 +643,14 @@ gst_v4l2_video_dec_setup_capture (GstVideoDecoder * decoder)
     output_state->info.interlace_mode = info.interlace_mode;
     output_state->info.colorimetry = info.colorimetry;
     gst_video_codec_state_unref (output_state);
+
+    cpool = gst_v4l2_object_get_buffer_pool (self->v4l2capture);
     gst_v4l2_buffer_pool_enable_resolution_change (GST_V4L2_BUFFER_POOL
-        (self->v4l2capture->pool));
+        (cpool));
 
     if (!gst_video_decoder_negotiate (decoder)) {
+      if (cpool)
+        gst_object_unref (cpool);
       if (GST_PAD_IS_FLUSHING (decoder->srcpad))
         goto flushing;
       else
@@ -646,8 +658,10 @@ gst_v4l2_video_dec_setup_capture (GstVideoDecoder * decoder)
     }
 
     /* Ensure our internal pool is activated */
-    if (!gst_buffer_pool_set_active (GST_BUFFER_POOL (self->v4l2capture->pool),
+    active = gst_buffer_pool_set_active (cpool, TRUE);
-            TRUE))
+    if (cpool)
+      gst_object_unref (cpool);
+    if (!active)
       goto activate_failed;
   }
 
@@ -670,7 +684,6 @@ static void
 gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
 {
   GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
-  GstV4l2BufferPool *v4l2_pool;
   GstBufferPool *pool;
   GstVideoCodecFrame *frame;
   GstBuffer *buffer = NULL;
@@ -701,7 +714,6 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
 
   GST_LOG_OBJECT (decoder, "Allocate output buffer");
 
-  v4l2_pool = GST_V4L2_BUFFER_POOL (self->v4l2capture->pool);
   self->output_flow = GST_FLOW_OK;
 
   do {
@@ -730,7 +742,14 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
       goto beach;
 
     GST_LOG_OBJECT (decoder, "Process output buffer");
-    ret = gst_v4l2_buffer_pool_process (v4l2_pool, &buffer, NULL);
+    {
+      GstV4l2BufferPool *cpool =
+          GST_V4L2_BUFFER_POOL (gst_v4l2_object_get_buffer_pool
+          (self->v4l2capture));
+      ret = gst_v4l2_buffer_pool_process (cpool, &buffer, NULL);
+      if (cpool)
+        gst_object_unref (cpool);
+    }
 
     if (ret == GST_V4L2_FLOW_RESOLUTION_CHANGE) {
       GST_INFO_OBJECT (decoder, "Received resolution change");
@@ -825,7 +844,7 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
 {
   GstV4l2Error error = GST_V4L2_ERROR_INIT;
   GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
-  GstBufferPool *pool = GST_BUFFER_POOL (self->v4l2output->pool);
+  GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
   GstFlowReturn ret = GST_FLOW_OK;
   gboolean processed = FALSE;
   GstBuffer *tmp;
@@ -900,8 +919,7 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
     GST_LOG_OBJECT (decoder, "Passing buffer with system frame number %u",
         processed ? frame->system_frame_number : 0);
     ret =
-        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->
+        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (pool), &codec_data,
-            v4l2output->pool), &codec_data,
         processed ? &frame->system_frame_number : &dummy_frame_number);
     GST_VIDEO_DECODER_STREAM_LOCK (decoder);
 
@@ -933,8 +951,8 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
     GST_LOG_OBJECT (decoder, "Passing buffer with system frame number %u",
         frame->system_frame_number);
     ret =
-        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->v4l2output->
+        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (pool),
-            pool), &frame->input_buffer, &frame->system_frame_number);
+        &frame->input_buffer, &frame->system_frame_number);
     GST_VIDEO_DECODER_STREAM_LOCK (decoder);
 
     if (ret == GST_FLOW_FLUSHING) {
@@ -956,6 +974,8 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
   gst_buffer_unref (tmp);
 
   gst_video_codec_frame_unref (frame);
+  if (pool)
+    gst_object_unref (pool);
   return ret;
 
   /* ERRORS */
@@ -997,6 +1017,8 @@ process_failed:
   }
 drop:
   {
+    if (pool)
+      gst_object_unref (pool);
     gst_video_decoder_drop_frame (decoder, frame);
     return ret;
   }

subprojects/gst-plugins-good/sys/v4l2/gstv4l2videoenc.c

@@ -652,10 +652,14 @@ gst_v4l2_video_enc_loop (GstVideoEncoder * encoder)
   /* FIXME Check if buffer isn't the last one here */
 
   GST_LOG_OBJECT (encoder, "Process output buffer");
-  ret =
+  {
-      gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL
+    GstV4l2BufferPool *cpool =
-      (self->v4l2capture->pool), &buffer, NULL);
+        GST_V4L2_BUFFER_POOL (gst_v4l2_object_get_buffer_pool
-
+        (self->v4l2capture));
+    ret = gst_v4l2_buffer_pool_process (cpool, &buffer, NULL);
+    if (cpool)
+      gst_object_unref (cpool);
+  }
   if (ret != GST_FLOW_OK)
     goto beach;
 
@@ -741,6 +745,7 @@ gst_v4l2_video_enc_handle_frame (GstVideoEncoder * encoder,
   GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
   GstFlowReturn ret = GST_FLOW_OK;
   GstTaskState task_state;
+  gboolean active;
 
   GST_DEBUG_OBJECT (self, "Handling frame %d", frame->system_frame_number);
 
@@ -749,7 +754,7 @@ gst_v4l2_video_enc_handle_frame (GstVideoEncoder * encoder,
 
   task_state = gst_pad_get_task_state (GST_VIDEO_ENCODER_SRC_PAD (self));
   if (task_state == GST_TASK_STOPPED || task_state == GST_TASK_PAUSED) {
-    GstBufferPool *pool = GST_BUFFER_POOL (self->v4l2output->pool);
+    GstBufferPool *pool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
 
     /* It is possible that the processing thread stopped due to an error or
      * when the last buffer has been met during the draining process. */
@@ -759,6 +764,8 @@ gst_v4l2_video_enc_handle_frame (GstVideoEncoder * encoder,
       GST_DEBUG_OBJECT (self, "Processing loop stopped with error: %s, leaving",
           gst_flow_get_name (self->output_flow));
       ret = self->output_flow;
+      if (pool)
+        gst_object_unref (pool);
       goto drop;
     }
 
@@ -772,15 +779,29 @@ gst_v4l2_video_enc_handle_frame (GstVideoEncoder * encoder,
           self->v4l2output->info.size, min, min);
 
       /* There is no reason to refuse this config */
-      if (!gst_buffer_pool_set_config (pool, config))
+      if (!gst_buffer_pool_set_config (pool, config)) {
-        goto activate_failed;
+        if (pool)
-
+          gst_object_unref (pool);
-      if (!gst_buffer_pool_set_active (pool, TRUE))
         goto activate_failed;
       }
 
-    if (!gst_buffer_pool_set_active
+      if (!gst_buffer_pool_set_active (pool, TRUE)) {
-        (GST_BUFFER_POOL (self->v4l2capture->pool), TRUE)) {
+        if (pool)
+          gst_object_unref (pool);
+        goto activate_failed;
+      }
+      if (pool)
+        gst_object_unref (pool);
+    }
+
+    {
+      GstBufferPool *cpool =
+          gst_v4l2_object_get_buffer_pool (self->v4l2capture);
+      active = gst_buffer_pool_set_active (cpool, TRUE);
+      if (cpool)
+        gst_object_unref (cpool);
+    }
+    if (!active) {
       GST_WARNING_OBJECT (self, "Could not activate capture buffer pool.");
       goto activate_failed;
     }
@@ -799,10 +820,15 @@ gst_v4l2_video_enc_handle_frame (GstVideoEncoder * encoder,
     GST_VIDEO_ENCODER_STREAM_UNLOCK (encoder);
     GST_LOG_OBJECT (encoder, "Passing buffer with frame number %u",
         frame->system_frame_number);
-    ret =
+
-        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->
+    {
-            v4l2output->pool), &frame->input_buffer,
+      GstBufferPool *opool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
-        &frame->system_frame_number);
+      ret = gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (opool),
+          &frame->input_buffer, &frame->system_frame_number);
+      if (opool)
+        gst_object_unref (opool);
+    }
+
     GST_VIDEO_ENCODER_STREAM_LOCK (encoder);
 
     if (ret == GST_FLOW_FLUSHING) {