paaudio: wait until the recording stream is ready

Don't call pa_stream_peek before the recording stream is ready.

Information to reproduce the problem.

Start and stop Audacity in the guest several times because the
problem is racy.

libvirt log file:
-audiodev pa,id=audio0,server=localhost,out.latency=30000,
 out.mixing-engine=off,in.mixing-engine=off \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,
 resourcecontrol=deny \
-msg timestamp=on
: Domain id=4 is tainted: custom-argv
char device redirected to /dev/pts/1 (label charserial0)
audio: Device pcspk: audiodev default parameter is deprecated,
 please specify audiodev=audio0
audio: Device hda: audiodev default parameter is deprecated,
 please specify audiodev=audio0
pulseaudio: pa_stream_peek failed
pulseaudio: Reason: Bad state
pulseaudio: pa_stream_peek failed
pulseaudio: Reason: Bad state

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20200104091122.13971-5-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

audio/paaudio.c

@@ -162,6 +162,10 @@ static size_t qpa_read(HWVoiceIn *hw, void *data, size_t length)
 
     CHECK_DEAD_GOTO(c, p->stream, unlock_and_fail,
                     "pa_threaded_mainloop_lock failed\n");
+    if (pa_stream_get_state(p->stream) != PA_STREAM_READY) {
+        /* wait for stream to become ready */
+        goto unlock;
+    }
 
     while (total < length) {
         size_t l;
@@ -191,6 +195,7 @@ static size_t qpa_read(HWVoiceIn *hw, void *data, size_t length)
         }
     }
 
+unlock:
     pa_threaded_mainloop_unlock(c->mainloop);
     return total;