The branch main has been updated by christos: URL: https://cgit.FreeBSD.org/src/commit/?id=24576c39789ca13846b9450155923ee0e377aeb4
commit 24576c39789ca13846b9450155923ee0e377aeb4 Author: Goran Mekić <[email protected]> AuthorDate: 2026-07-06 12:06:17 +0000 Commit: Christos Margiolis <[email protected]> CommitDate: 2026-07-06 12:07:41 +0000 sound: track kqueue low watermark per-knote for mmaped channels Use kn->kn_sdata to track the last bs->total value for each knote attached to an mmaped channel. An event is delivered only when the total byte counter has advanced by at least c->lw since the last delivery. After delivery kn_sdata is updated to the current total. Each knote tracks its own watermark independently, so multiple knotes attached to the same mmaped channel all receive events correctly. Non-mmap channels keep the existing level-triggered behavior via chn_polltrigger(). MFC after: 1 week Reviewed by: christos Differential Revision: https://reviews.freebsd.org/D57833 --- sys/dev/sound/pcm/channel.c | 14 +++++++++----- sys/dev/sound/pcm/channel.h | 2 +- sys/dev/sound/pcm/dsp.c | 14 +++++++++++++- 3 files changed, 23 insertions(+), 7 deletions(-) diff --git a/sys/dev/sound/pcm/channel.c b/sys/dev/sound/pcm/channel.c index a0ee16a14386..40a08d48fb21 100644 --- a/sys/dev/sound/pcm/channel.c +++ b/sys/dev/sound/pcm/channel.c @@ -270,11 +270,15 @@ chn_lockdestroy(struct pcm_channel *c) /** * @brief Determine channel is ready for I/O * + * @param ref_total for mmaped channels, the previous byte counter + * * snapshot from which to compute the delta to + * * bufsoft->total; ignored for non-mmaped channels. + * * @retval 1 = ready for I/O * @retval 0 = not ready for I/O */ int -chn_polltrigger(struct pcm_channel *c) +chn_polltrigger(struct pcm_channel *c, u_int64_t ref_total) { struct snd_dbuf *bs = c->bufsoft; u_int delta; @@ -282,10 +286,10 @@ chn_polltrigger(struct pcm_channel *c) CHN_LOCKASSERT(c); if (c->flags & CHN_F_MMAP) { - if (bs->prev_total < c->lw) + if (ref_total < c->lw) delta = c->lw; else - delta = bs->total - bs->prev_total; + delta = bs->total - ref_total; } else { if (c->direction == PCMDIR_PLAY) delta = sndbuf_getfree(bs); @@ -316,7 +320,7 @@ chn_wakeup(struct pcm_channel *c) if (CHN_EMPTY(c, children.busy)) { KNOTE_LOCKED(&bs->sel.si_note, 0); - if (SEL_WAITING(&bs->sel) && chn_polltrigger(c)) + if (SEL_WAITING(&bs->sel) && chn_polltrigger(c, bs->prev_total)) selwakeuppri(&bs->sel, PRIBIO); CHN_BROADCAST(&c->intr_cv); } else { @@ -830,7 +834,7 @@ chn_poll(struct pcm_channel *c, int ev, struct thread *td) } ret = 0; - if (chn_polltrigger(c)) { + if (chn_polltrigger(c, bs->prev_total)) { chn_pollreset(c); ret = ev; } else diff --git a/sys/dev/sound/pcm/channel.h b/sys/dev/sound/pcm/channel.h index 6fa4338dce4a..c7f5bf93b8e5 100644 --- a/sys/dev/sound/pcm/channel.h +++ b/sys/dev/sound/pcm/channel.h @@ -260,7 +260,7 @@ int chn_read(struct pcm_channel *c, struct uio *buf); u_int32_t chn_start(struct pcm_channel *c, int force); int chn_sync(struct pcm_channel *c, int threshold); int chn_flush(struct pcm_channel *c); -int chn_polltrigger(struct pcm_channel *c); +int chn_polltrigger(struct pcm_channel *c, u_int64_t ref_total); int chn_poll(struct pcm_channel *c, int ev, struct thread *td); char *chn_mkname(char *buf, size_t len, struct pcm_channel *c); diff --git a/sys/dev/sound/pcm/dsp.c b/sys/dev/sound/pcm/dsp.c index 8bb07d87fac9..da8bf485bc9b 100644 --- a/sys/dev/sound/pcm/dsp.c +++ b/sys/dev/sound/pcm/dsp.c @@ -3010,7 +3010,13 @@ dsp_kqevent(struct knote *kn, long hint) return (1); } kn->kn_data = 0; - if (chn_polltrigger(ch)) { + /* + * For mmaped channels pass the knote's own reference point so the + * low watermark is tracked per-knote. Non-mmaped channels ignore + * the reference and fire based on the current amount of ready/free + * data in the buffer, so all knotes see the same live state. + */ + if (chn_polltrigger(ch, (u_int64_t)kn->kn_sdata)) { if (kn->kn_filter == EVFILT_READ) { kn->kn_data = sndbuf_getready(ch->bufsoft); if (ch->flags & CHN_F_MMAP) @@ -3025,6 +3031,7 @@ dsp_kqevent(struct knote *kn, long hint) kn->kn_kevent.ext[0] = sndbuf_getready(ch->bufsoft) / ch->bufsoft->align; } kn->kn_kevent.ext[1] = ch->xruns; + kn->kn_sdata = ch->bufsoft->total; } return (kn->kn_data > 0); @@ -3070,6 +3077,11 @@ dsp_kqfilter(struct cdev *dev, struct knote *kn) knlist_add(&ch->bufsoft->sel.si_note, kn, 1); CHN_UNLOCK(ch); kn->kn_hook = ch; + /* + * Start tracking from the current position so the first event + * fires after c->lw additional bytes have been transferred. + */ + kn->kn_sdata = ch->bufsoft->prev_total; } else err = EINVAL; PCM_GIANT_LEAVE(d);
