In case the rewind did not rewind as much as expected, e g due to time delay between the latest avail update and the rewind, we must properly account for that in the plugin layer.
Otherwise, the plugin's appl ptr and the hw's appl ptr become unsynchronised, which is very bad, especially in mmap_shadow plugins, e g, this could cause the overlapping memcpy in the softvol plugin as seen here: https://bugs.freedesktop.org/show_bug.cgi?id=64299
Signed-off-by: David Henningsson david.henningsson@canonical.com --- src/pcm/pcm_plugin.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
Btw, I was also considering always syncing the appl.ptr (for playback) with the slave in snd_pcm_plugin_avail_update, like we do for the hw.ptr. Do you think this would be a good idea?
diff --git a/src/pcm/pcm_plugin.c b/src/pcm/pcm_plugin.c index 96218a8..17157e8 100644 --- a/src/pcm/pcm_plugin.c +++ b/src/pcm/pcm_plugin.c @@ -219,9 +219,9 @@ static snd_pcm_sframes_t snd_pcm_plugin_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t snd_atomic_write_end(&plugin->watom); return sframes; } - snd_pcm_mmap_appl_backward(pcm, (snd_pcm_uframes_t) frames); + snd_pcm_mmap_appl_backward(pcm, (snd_pcm_uframes_t) sframes); snd_atomic_write_end(&plugin->watom); - return (snd_pcm_sframes_t) frames; + return (snd_pcm_sframes_t) sframes; }
static snd_pcm_sframes_t snd_pcm_plugin_forwardable(snd_pcm_t *pcm)