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[PATCH] Fix a race condition accessing the decode_chain field.

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Make sure that any access to the GstDecodeBin's decode_chain
field is protected using the EXPOSE_LOCK.  Also add a simple
reference counter to the GstDecodeChain structure so that when
the type_found signal fires it can hold onto the decode chain
even while the EXPOSE_LOCK is not held.  This should fix a
race condition if the type_found signal fires right in the
middle of a state change that messes with the same decode
chain.

https://bugzilla.gnome.org/show_bug.cgi?id=755260
This commit is contained in:
Thomas Bluemel 2015-11-06 14:21:14 +00:00 committed by Vincent Penquerc'h
parent 870c6df489
commit 2c62aad159
1 changed files with 40 additions and 16 deletions
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46
gst/playback/gstdecodebin2.c
View file

@ -419,6 +419,8 @@ struct _GstDecodeChain
GstDecodeGroup *parent;
GstDecodeBin *dbin;
gint refs; /* Number of references to this object */
GMutex lock; /* Protects this chain and its groups */
GstPad *pad; /* srcpad that caused creation of this chain */
@ -459,6 +461,8 @@ struct _GstDecodeChain
GList *old_groups; /* Groups that should be freed later */
};
static GstDecodeChain *gst_decode_chain_ref (GstDecodeChain * chain);
static void gst_decode_chain_unref (GstDecodeChain * chain);
static void gst_decode_chain_free (GstDecodeChain * chain);
static GstDecodeChain *gst_decode_chain_new (GstDecodeBin * dbin,
GstDecodeGroup * group, GstPad * pad);
@ -2794,6 +2798,7 @@ type_found (GstElement * typefind, guint probability,
GstCaps * caps, GstDecodeBin * decode_bin)
{
GstPad *pad, *sink_pad;
GstDecodeChain *chain;
GST_DEBUG_OBJECT (decode_bin, "typefind found caps %" GST_PTR_FORMAT, caps);
@ -2808,13 +2813,6 @@ type_found (GstElement * typefind, guint probability,
}
EXPOSE_LOCK (decode_bin);
/* FIXME: we can only deal with one type, we don't yet support dynamically changing
* caps from the typefind element */
if (decode_bin->have_type || decode_bin->decode_chain)
goto exit;
decode_bin->have_type = TRUE;
pad = gst_element_get_static_pad (typefind, "src");
sink_pad = gst_element_get_static_pad (typefind, "sink");
@ -2823,11 +2821,22 @@ type_found (GstElement * typefind, guint probability,
* In typical cases, STREAM_LOCK is held and handles that, it need not
* be held (if called from a proxied setcaps), so grab it anyway */
GST_PAD_STREAM_LOCK (sink_pad);
/* FIXME: we can only deal with one type, we don't yet support dynamically changing
* caps from the typefind element */
if (decode_bin->have_type || decode_bin->decode_chain) {
} else {
decode_bin->have_type = TRUE;
decode_bin->decode_chain = gst_decode_chain_new (decode_bin, NULL, pad);
chain = gst_decode_chain_ref (decode_bin->decode_chain);
if (analyze_new_pad (decode_bin, typefind, pad, caps,
decode_bin->decode_chain, NULL))
expose_pad (decode_bin, typefind, decode_bin->decode_chain->current_pad,
pad, caps, decode_bin->decode_chain, FALSE);
gst_decode_chain_unref (chain);
}
GST_PAD_STREAM_UNLOCK (sink_pad);
gst_object_unref (sink_pad);
@ -3283,6 +3292,22 @@ gst_decode_chain_get_current_group (GstDecodeChain * chain)
static void gst_decode_group_free_internal (GstDecodeGroup * group,
gboolean hide);
static void
gst_decode_chain_unref (GstDecodeChain * chain)
{
if (g_atomic_int_dec_and_test (&chain->refs)) {
g_mutex_clear (&chain->lock);
g_slice_free (GstDecodeChain, chain);
}
}
static GstDecodeChain *
gst_decode_chain_ref (GstDecodeChain * chain)
{
g_atomic_int_inc (&chain->refs);
return chain;
}
static void
gst_decode_chain_free_internal (GstDecodeChain * chain, gboolean hide)
{
@ -3423,10 +3448,8 @@ gst_decode_chain_free_internal (GstDecodeChain * chain, gboolean hide)
gst_object_unref (element);
}
if (!hide) {
g_mutex_clear (&chain->lock);
g_slice_free (GstDecodeChain, chain);
}
if (!hide)
gst_decode_chain_unref (chain);
}
/* gst_decode_chain_free:
@ -3461,6 +3484,7 @@ gst_decode_chain_new (GstDecodeBin * dbin, GstDecodeGroup * parent,
chain->dbin = dbin;
chain->parent = parent;
chain->refs = 1;
g_mutex_init (&chain->lock);
chain->pad = gst_object_ref (pad);