ladspa-sink: Set a silence memchunk for the memblockq

A crash was observed that was caused by pa_memblockq_peek() returning
a NULL memblock in sink_input_pop_cb(). The scenario where this was
happening was

1. Delete 2 rtp-recv's connected to a ladspa-sink
2. Delete ladspa-sink
3. Delete alsa-sink
4. Create alsa-sink
5. Create ladspa-sink
6. Create 2 rtp-recv's connected to the ladspa-sink

The crash was probably caused by a rewind that made the read index go
negative while the write index was at least zero, causing there to be
a gap in the memblockq. The problematic rewind might have been caused
by adding the rtp-recv stream to the ladspa-sink. That has not been
proven, but this looks very similar to the bug that was fixed in
module-virtual-sink in commit 6bd34156b130c07b130de10111a12ef6dab18b52.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/modules/module-ladspa-sink.c b/src/modules/module-ladspa-sink.c
index 8e35b1b6d..46ce9e440 100644
--- a/src/modules/module-ladspa-sink.c
+++ b/src/modules/module-ladspa-sink.c
@@ -966,6 +966,7 @@ int pa__init(pa_module*m) {
     const char *e, *cdata;
     const LADSPA_Descriptor *d;
     unsigned long p, h, j, n_control, c;
+    pa_memchunk silence;
 
     pa_assert(m);
 
@@ -1010,7 +1011,6 @@ int pa__init(pa_module*m) {
     u = pa_xnew0(struct userdata, 1);
     u->module = m;
     m->userdata = u;
-    u->memblockq = pa_memblockq_new("module-ladspa-sink memblockq", 0, MEMBLOCKQ_MAXLENGTH, 0, &ss, 1, 1, 0, NULL);
     u->max_ladspaport_count = 1; /*to avoid division by zero etc. in pa__done when failing before this value has been set*/
     u->channels = 0;
     u->input = NULL;
@@ -1293,6 +1293,10 @@ int pa__init(pa_module*m) {
 
     u->sink->input_to_master = u->sink_input;
 
+    pa_sink_input_get_silence(u->sink_input, &silence);
+    u->memblockq = pa_memblockq_new("module-ladspa-sink memblockq", 0, MEMBLOCKQ_MAXLENGTH, 0, &ss, 1, 1, 0, &silence);
+    pa_memblock_unref(silence.memblock);
+
     pa_sink_put(u->sink);
     pa_sink_input_put(u->sink_input);