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sound/midi: midi_poll is always failing. #1887

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sound/midi: midi_poll is always failing. #1887

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20 changes: 9 additions & 11 deletions sys/dev/sound/midi/midi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -658,21 +658,19 @@ midi_poll(struct cdev *i_dev, int events, struct thread *td)
mtx_lock(&m->lock);
mtx_lock(&m->qlock);

if (events & (POLLIN | POLLRDNORM))
if (events & (POLLIN | POLLRDNORM)) {
if (!MIDIQ_EMPTY(m->inq))
events |= events & (POLLIN | POLLRDNORM);

if (events & (POLLOUT | POLLWRNORM))
if (MIDIQ_AVAIL(m->outq) < m->hiwat)
events |= events & (POLLOUT | POLLWRNORM);

if (revents == 0) {
if (events & (POLLIN | POLLRDNORM))
revents |= events & (POLLIN | POLLRDNORM);
else
selrecord(td, &m->rsel);

if (events & (POLLOUT | POLLWRNORM))
}
if (events & (POLLOUT | POLLWRNORM)) {
if (MIDIQ_AVAIL(m->outq) < m->hiwat)
revents |= events & (POLLOUT | POLLWRNORM);
else
selrecord(td, &m->wsel);
}

mtx_unlock(&m->lock);
mtx_unlock(&m->qlock);
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@christosmarg christosmarg Nov 24, 2025

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Not related to the patch, but I'm pretty sure there is a lock order reversal here. Have you tested this code path? If there is, I can propose a patch. Let me know.

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@n-p-soft n-p-soft Nov 24, 2025 •
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I just swapped these unlocks, seems strange to me. Anyway let restore the right order.

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@christosmarg christosmarg Nov 24, 2025

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You can open a new PR for this issue.


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