From: Cássio Gabriel Date: Tue, 26 May 2026 12:48:26 +0000 (-0300) Subject: ALSA: xen-front: Reset event channel state on stream clear X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9cd81152373c560b8aa8299b0705c4db82b103b7;p=thirdparty%2Flinux.git ALSA: xen-front: Reset event channel state on stream clear xen_snd_front_evtchnl_pair_clear() resets evt_next_id for both channels. That is correct for the request channel, where evt_next_id is used to allocate the next request id. It is wrong for the event channel: incoming events are validated against evt_id, and evt_id is incremented by evtchnl_interrupt_evt(). This leaves the expected event id from the previous stream instance. A backend that restarts event ids for a reopened stream can then have valid current-position events dropped until the stale frontend id catches up. Reset evt_id for the event channel. Also advance the event-page consumer to the current producer while clearing the stream, so obsolete events queued for the previous stream instance are not delivered to the next ALSA runtime. Fixes: 1cee559351a7 ("ALSA: xen-front: Implement ALSA virtual sound driver") Signed-off-by: Cássio Gabriel Link: https://patch.msgid.link/20260526-alsa-xen-event-channel-fixes-v1-1-91d3a6a50778@gmail.com Signed-off-by: Takashi Iwai --- diff --git a/sound/xen/xen_snd_front_evtchnl.c b/sound/xen/xen_snd_front_evtchnl.c index bc03f71bf16e3..09e4c1d056363 100644 --- a/sound/xen/xen_snd_front_evtchnl.c +++ b/sound/xen/xen_snd_front_evtchnl.c @@ -456,7 +456,11 @@ void xen_snd_front_evtchnl_pair_clear(struct xen_snd_front_evtchnl_pair *evt_pai } scoped_guard(mutex, &evt_pair->evt.ring_io_lock) { - evt_pair->evt.evt_next_id = 0; + evt_pair->evt.evt_id = 0; + /* Drop obsolete events queued for the previous stream instance. */ + evt_pair->evt.u.evt.page->in_cons = + evt_pair->evt.u.evt.page->in_prod; + /* Ensure the consumer index is visible before stream reuse. */ + virt_wmb(); } } - diff --git a/sound/xen/xen_snd_front_evtchnl.h b/sound/xen/xen_snd_front_evtchnl.h index 3675fba705647..8400261ac4660 100644 --- a/sound/xen/xen_snd_front_evtchnl.h +++ b/sound/xen/xen_snd_front_evtchnl.h @@ -37,9 +37,9 @@ struct xen_snd_front_evtchnl { /* State of the event channel. */ enum xen_snd_front_evtchnl_state state; enum xen_snd_front_evtchnl_type type; - /* Either response id or incoming event id. */ + /* Current response id or next expected incoming event id. */ u16 evt_id; - /* Next request id or next expected event id. */ + /* Next request id. */ u16 evt_next_id; /* Shared ring access lock. */ struct mutex ring_io_lock;