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| author | Cássio Gabriel <cassiogabrielcontato@gmail.com> | 2026-05-26 09:48:26 -0300 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2026-05-27 07:25:41 +0200 |
| commit | 9cd81152373c560b8aa8299b0705c4db82b103b7 (patch) | |
| tree | 11301cf7b4db79ad02b587ed5ed284d65e66ace0 | |
| parent | a23812004228d4b041a858b927db787a7ff80f50 (diff) | |
| download | linux-9cd81152373c560b8aa8299b0705c4db82b103b7.tar.gz linux-9cd81152373c560b8aa8299b0705c4db82b103b7.zip | |
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 <cassiogabrielcontato@gmail.com>
Link: https://patch.msgid.link/20260526-alsa-xen-event-channel-fixes-v1-1-91d3a6a50778@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
| -rw-r--r-- | sound/xen/xen_snd_front_evtchnl.c | 8 | ||||
| -rw-r--r-- | sound/xen/xen_snd_front_evtchnl.h | 4 |
2 files changed, 8 insertions, 4 deletions
diff --git a/sound/xen/xen_snd_front_evtchnl.c b/sound/xen/xen_snd_front_evtchnl.c index bc03f71bf16e..09e4c1d05636 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 3675fba70564..8400261ac466 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; |