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shmsrc: fixes a crash when is-live is true due a race condition

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There's a race condition when is-live is set to true and the shmsrc
element releases the pipe in the transition from PLAYING to PAUSED.
To avoid it this change ensures that _create method takes the pipe
and increases the use_count in one operation protected by object lock.
Also perform apropriate protections when releasing the pipe.

https://bugzilla.gnome.org/show_bug.cgi?id=797203
This commit is contained in:
Josep Torra 2018-09-28 13:35:49 +02:00 committed by Olivier Crête
parent 3f83205399
commit eb1665ff22
1 changed files with 42 additions and 27 deletions
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69
sys/shm/gstshmsrc.c
View file

@ -91,7 +91,6 @@ static gboolean gst_shm_src_unlock_stop (GstBaseSrc * bsrc);
static GstStateChangeReturn gst_shm_src_change_state (GstElement * element,
GstStateChange transition);
static void gst_shm_pipe_inc (GstShmPipe * pipe);
static void gst_shm_pipe_dec (GstShmPipe * pipe);
static void
@ -253,6 +252,7 @@ gst_shm_src_start_reading (GstShmSrc * self)
self->pipe = gstpipe;
self->unlocked = FALSE;
gst_poll_set_flushing (self->poll, FALSE);
gst_poll_fd_init (&self->pollfd);
@ -266,12 +266,17 @@ gst_shm_src_start_reading (GstShmSrc * self)
static void
gst_shm_src_stop_reading (GstShmSrc * self)
{
GstShmPipe *pipe;
GST_DEBUG_OBJECT (self, "Stopping %p", self);
if (self->pipe) {
gst_shm_pipe_dec (self->pipe);
self->pipe = NULL;
GST_OBJECT_LOCK (self);
pipe = self->pipe;
self->pipe = NULL;
GST_OBJECT_UNLOCK (self);
if (pipe) {
gst_shm_pipe_dec (pipe);
gst_poll_remove_fd (self->poll, &self->pollfd);
}
@ -320,44 +325,57 @@ static GstFlowReturn
gst_shm_src_create (GstPushSrc * psrc, GstBuffer ** outbuf)
{
GstShmSrc *self = GST_SHM_SRC (psrc);
GstShmPipe *pipe;
gchar *buf = NULL;
int rv = 0;
struct GstShmBuffer *gsb;
GST_DEBUG_OBJECT (self, "Stopping %p", self);
GST_OBJECT_LOCK (self);
pipe = self->pipe;
if (!pipe) {
GST_OBJECT_UNLOCK (self);
return GST_FLOW_FLUSHING;
} else {
pipe->use_count++;
}
GST_OBJECT_UNLOCK (self);
do {
if (gst_poll_wait (self->poll, GST_CLOCK_TIME_NONE) < 0) {
if (errno == EBUSY)
return GST_FLOW_FLUSHING;
goto flushing;
GST_ELEMENT_ERROR (self, RESOURCE, READ, ("Failed to read from shmsrc"),
("Poll failed on fd: %s", strerror (errno)));
return GST_FLOW_ERROR;
goto error;
}
if (self->unlocked)
return GST_FLOW_FLUSHING;
goto flushing;
if (gst_poll_fd_has_closed (self->poll, &self->pollfd)) {
GST_ELEMENT_ERROR (self, RESOURCE, READ, ("Failed to read from shmsrc"),
("Control socket has closed"));
return GST_FLOW_ERROR;
goto error;
}
if (gst_poll_fd_has_error (self->poll, &self->pollfd)) {
GST_ELEMENT_ERROR (self, RESOURCE, READ, ("Failed to read from shmsrc"),
("Control socket has error"));
return GST_FLOW_ERROR;
goto error;
}
if (gst_poll_fd_can_read (self->poll, &self->pollfd)) {
buf = NULL;
GST_LOG_OBJECT (self, "Reading from pipe");
GST_OBJECT_LOCK (self);
rv = sp_client_recv (self->pipe->pipe, &buf);
rv = sp_client_recv (pipe->pipe, &buf);
GST_OBJECT_UNLOCK (self);
if (rv < 0) {
GST_ELEMENT_ERROR (self, RESOURCE, READ, ("Failed to read from shmsrc"),
("Error reading control data: %d", rv));
return GST_FLOW_ERROR;
goto error;
}
}
} while (buf == NULL);
@ -366,13 +384,19 @@ gst_shm_src_create (GstPushSrc * psrc, GstBuffer ** outbuf)
gsb = g_slice_new0 (struct GstShmBuffer);
gsb->buf = buf;
gsb->pipe = self->pipe;
gst_shm_pipe_inc (self->pipe);
gsb->pipe = pipe;
*outbuf = gst_buffer_new_wrapped_full (GST_MEMORY_FLAG_READONLY,
buf, rv, 0, rv, gsb, free_buffer);
return GST_FLOW_OK;
error:
gst_shm_pipe_dec (pipe);
return GST_FLOW_ERROR;
flushing:
gst_shm_pipe_dec (pipe);
return GST_FLOW_FLUSHING;
}
static GstStateChangeReturn
@ -383,9 +407,10 @@ gst_shm_src_change_state (GstElement * element, GstStateChange transition)
switch (transition) {
case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
if (gst_base_src_is_live (GST_BASE_SRC (element)))
if (gst_base_src_is_live (GST_BASE_SRC (element))) {
if (!gst_shm_src_start_reading (self))
return GST_STATE_CHANGE_FAILURE;
}
default:
break;
}
@ -396,8 +421,10 @@ gst_shm_src_change_state (GstElement * element, GstStateChange transition)
switch (transition) {
case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
if (gst_base_src_is_live (GST_BASE_SRC (element)))
if (gst_base_src_is_live (GST_BASE_SRC (element))) {
gst_shm_src_unlock (GST_BASE_SRC (element));
gst_shm_src_stop_reading (self);
}
default:
break;
}
@ -427,18 +454,6 @@ gst_shm_src_unlock_stop (GstBaseSrc * bsrc)
return TRUE;
}
static void
gst_shm_pipe_inc (GstShmPipe * pipe)
{
g_return_if_fail (pipe);
g_return_if_fail (pipe->src);
g_return_if_fail (pipe->use_count > 0);
GST_OBJECT_LOCK (pipe->src);
pipe->use_count++;
GST_OBJECT_UNLOCK (pipe->src);
}
static void
gst_shm_pipe_dec (GstShmPipe * pipe)
{