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fix(alsa): drop PCM IO before underrun recovery #1401

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fix(alsa): drop PCM IO before underrun recovery #1401

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17 changes: 11 additions & 6 deletions src/host/alsa/duplex.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -349,12 +349,15 @@ fn process_duplex(
) -> Result<(), Error> {
let mut frames_read = 0;
while frames_read < stream.period_size {
match stream
// Bind the result first: an IO in a match scrutinee lives across the arms, and
// alsa allows only one IO per PCM, so recover_duplex() -> begin_duplex_playback()
// would panic creating a second IO on the playback PCM.
let result = stream
.capture
.handle
.io_bytes()
.readi(&mut capture_buffer[frames_read * stream.capture.frame_size..])
{
.readi(&mut capture_buffer[frames_read * stream.capture.frame_size..]);
match result {
Ok(n) => frames_read += n,
Err(err) if err.errno() == libc::EAGAIN && frames_read == 0 => return Ok(()),
Err(_) if matches!(stream.capture.handle.state(), alsa::pcm::State::Suspended) => {
Expand Down Expand Up @@ -431,12 +434,14 @@ fn process_duplex(

let mut frames_written = 0;
while frames_written < stream.period_size {
match stream
// Bind the result first, as for capture above: recover_duplex() must not run
// while this PCM's IO is still alive.
let result = stream
.playback
.handle
.io_bytes()
.writei(&playback_buffer[frames_written * stream.playback.frame_size..])
{
.writei(&playback_buffer[frames_written * stream.playback.frame_size..]);
match result {
Ok(n) => frames_written += n,
Err(err) if err.errno() == libc::EAGAIN && frames_written == 0 => return Ok(()),
Err(_) if matches!(stream.playback.handle.state(), alsa::pcm::State::Suspended) => {
Expand Down
16 changes: 10 additions & 6 deletions src/host/alsa/worker.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -334,11 +334,13 @@ fn process_input(
) -> Result<(), Error> {
let mut frames_read = 0;
while frames_read < stream.period_size {
match stream
// Bind the result first: an IO in a match scrutinee lives across the arms, and
// alsa allows only one IO per PCM, so recovery must not run while it is alive.
let result = stream
.handle
.io_bytes()
.readi(&mut buffer[frames_read * stream.frame_size..])
{
.readi(&mut buffer[frames_read * stream.frame_size..]);
match result {
Ok(n) => frames_read += n,
// EAGAIN = no frames available: skip this cycle if no progress was made,
// otherwise treat as an underrun (partial period cannot be delivered safely).
Expand Down Expand Up @@ -419,11 +421,13 @@ fn process_output(

let mut frames_written = 0;
while frames_written < stream.period_size {
match stream
// Bind the result first, as for input above: recovery must not run while
// this PCM's IO is still alive.
let result = stream
.handle
.io_bytes()
.writei(&buffer[frames_written * stream.frame_size..])
{
.writei(&buffer[frames_written * stream.frame_size..]);
match result {
Ok(n) => frames_written += n,
// EAGAIN = device cannot currently accept more frames: skip this cycle if no
// progress was made, otherwise treat as an underrun (partial period cannot be
Expand Down
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