This is a fix for a data race leading to:
> GLib-CRITICAL: g_hash_table_foreach:
> assertion 'version == hash_table->version' failed
Identified sequence:
* `rtp_session_on_timeout` acquires the lock on `session` and proceeds with its
processing.
* `rtp_session_process_rtcp` is called (debug log : received RTCP packet) and
attempts to acquire the lock on `session`, which is still held by
`rtp_session_on_timeout`.
* as part of an hash table iterator, `rtp_session_on_timeout` transitively
invokes `source_caps` which releases the lock on `session` so as to call
`session->callbacks.caps`.
* Since `rtp_session_process_rtcp` was waiting for the lock to be released, it
succeeds in acquiring it and proceeds with `rtp_session_process_rr` which
transitively calls `g_hash_table_insert` via `add_source`.
* After `source_caps` re-acquires the lock and gives the control flow back to
`rtp_session_on_timeout`, the hash table iterator is changed, resulting in the
assertion failure.
This commits copies `sess->ssrcs[sess->mask_idx]` and iterates on the copy so
the iterator is not affected by a concurrent change due to the lock being
released in the `source_caps` callback.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4585>
/* check if all the buffers are empty after generation */
all_empty = TRUE;
/* check if all the buffers are empty after generation */
all_empty = TRUE;
+ /* Make a local copy of the hashtable. We need to do this because the
+ * generate_rtcp stage below releases the session lock. */
+ table_copy = g_hash_table_new_full (NULL, NULL, NULL,
+ (GDestroyNotify) g_object_unref);
+ g_hash_table_foreach (sess->ssrcs[sess->mask_idx],
+ (GHFunc) clone_ssrcs_hashtable, table_copy);
+
GST_DEBUG
("doing RTCP generation %u for %u sources, early %d, may suppress %d",
sess->generation, data.num_to_report, data.is_early, data.may_suppress);
GST_DEBUG
("doing RTCP generation %u for %u sources, early %d, may suppress %d",
sess->generation, data.num_to_report, data.is_early, data.may_suppress);
- /* generate RTCP for all internal sources */
- g_hash_table_foreach (sess->ssrcs[sess->mask_idx],
- (GHFunc) generate_rtcp, &data);
+ /* generate RTCP for all internal sources, this might release the
+ * session lock. */
+ g_hash_table_foreach (table_copy, (GHFunc) generate_rtcp, &data);
- g_hash_table_foreach (sess->ssrcs[sess->mask_idx],
- (GHFunc) generate_twcc, &data);
+ g_hash_table_foreach (table_copy, (GHFunc) generate_twcc, &data);
/* update the generation for all the sources that have been reported */
/* update the generation for all the sources that have been reported */
- g_hash_table_foreach (sess->ssrcs[sess->mask_idx],
- (GHFunc) update_generation, &data);
+ g_hash_table_foreach (table_copy, (GHFunc) update_generation, &data);
+
+ g_hash_table_destroy (table_copy);
/* we keep track of the last report time in order to timeout inactive
* receivers or senders */
/* we keep track of the last report time in order to timeout inactive
* receivers or senders */