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pad: Fix race between gst_element_remove_pad and state change

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When going from READY to NULL all element pads are deactivated. If
simultaneously the pad is being removed from the element with
gst_element_remove_pad() and the pad is unparented, there is a race
where the deactivation will assert (g_critical) if the parent is lost at
the wrong time.

The proposed fix will check parent only once and retain it to avoid the
race.

https://bugzilla.gnome.org/show_bug.cgi?id=761912
This commit is contained in:
Stian Selnes 2016-01-27 11:46:06 +01:00 committed by Sebastian Dröge
parent 9b0d42ceec
commit 7dd76b626e
1 changed files with 52 additions and 32 deletions
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84
gst/gstpad.c
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@ -186,6 +186,9 @@ static GstFlowReturn gst_pad_send_event_unchecked (GstPad * pad,
static GstFlowReturn gst_pad_push_event_unchecked (GstPad * pad,
GstEvent * event, GstPadProbeType type);
static gboolean activate_mode_internal (GstPad * pad, GstObject * parent,
GstPadMode mode, gboolean active);
static guint gst_pad_signals[LAST_SIGNAL] = { 0 };
static GParamSpec *pspec_caps = NULL;
@ -924,7 +927,9 @@ gst_pad_get_direction (GstPad * pad)
static gboolean
gst_pad_activate_default (GstPad * pad, GstObject * parent)
{
return gst_pad_activate_mode (pad, GST_PAD_MODE_PUSH, TRUE);
g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
return activate_mode_internal (pad, parent, GST_PAD_MODE_PUSH, TRUE);
}
/**
@ -1069,7 +1074,7 @@ gst_pad_set_active (GstPad * pad, gboolean active)
} else {
GST_DEBUG_OBJECT (pad, "deactivating pad from %s mode",
gst_pad_mode_get_name (old));
ret = gst_pad_activate_mode (pad, old, FALSE);
ret = activate_mode_internal (pad, parent, old, FALSE);
if (ret)
pad->ABI.abi.last_flowret = GST_FLOW_FLUSHING;
}
@ -1103,36 +1108,18 @@ failed:
}
}
/**
* gst_pad_activate_mode:
* @pad: the #GstPad to activate or deactivate.
* @mode: the requested activation mode
* @active: whether or not the pad should be active.
*
* Activates or deactivates the given pad in @mode via dispatching to the
* pad's activatemodefunc. For use from within pad activation functions only.
*
* If you don't know what this is, you probably don't want to call it.
*
* Returns: %TRUE if the operation was successful.
*
* MT safe.
*/
gboolean
gst_pad_activate_mode (GstPad * pad, GstPadMode mode, gboolean active)
static gboolean
activate_mode_internal (GstPad * pad, GstObject * parent, GstPadMode mode,
gboolean active)
{
gboolean res = FALSE;
GstObject *parent;
GstPadMode old, new;
GstPadDirection dir;
GstPad *peer;
g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
GST_OBJECT_LOCK (pad);
old = GST_PAD_MODE (pad);
dir = GST_PAD_DIRECTION (pad);
ACQUIRE_PARENT (pad, parent, no_parent);
GST_OBJECT_UNLOCK (pad);
new = active ? mode : GST_PAD_MODE_NONE;
@ -1146,7 +1133,7 @@ gst_pad_activate_mode (GstPad * pad, GstPadMode mode, gboolean active)
GST_DEBUG_OBJECT (pad, "deactivating pad from %s mode",
gst_pad_mode_get_name (old));
if (G_UNLIKELY (!gst_pad_activate_mode (pad, old, FALSE)))
if (G_UNLIKELY (!activate_mode_internal (pad, parent, old, FALSE)))
goto deactivate_failed;
}
@ -1209,16 +1196,8 @@ exit_success:
}
exit:
RELEASE_PARENT (parent);
return res;
no_parent:
{
GST_DEBUG_OBJECT (pad, "no parent");
GST_OBJECT_UNLOCK (pad);
return FALSE;
}
was_ok:
{
GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad, "already %s in %s mode",
@ -1260,6 +1239,47 @@ failure:
}
}
/**
* gst_pad_activate_mode:
* @pad: the #GstPad to activate or deactivate.
* @mode: the requested activation mode
* @active: whether or not the pad should be active.
*
* Activates or deactivates the given pad in @mode via dispatching to the
* pad's activatemodefunc. For use from within pad activation functions only.
*
* If you don't know what this is, you probably don't want to call it.
*
* Returns: %TRUE if the operation was successful.
*
* MT safe.
*/
gboolean
gst_pad_activate_mode (GstPad * pad, GstPadMode mode, gboolean active)
{
GstObject *parent;
gboolean res;
g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
GST_OBJECT_LOCK (pad);
ACQUIRE_PARENT (pad, parent, no_parent);
GST_OBJECT_UNLOCK (pad);
res = activate_mode_internal (pad, parent, mode, active);
RELEASE_PARENT (parent);
return res;
no_parent:
{
GST_WARNING_OBJECT (pad, "no parent");
GST_OBJECT_UNLOCK (pad);
return FALSE;
}
}
/**
* gst_pad_is_active:
* @pad: the #GstPad to query