snd_usb_queue_pending_output_urbs() may be called from snd_pcm_ops::ack() which means the PCM stream is locked.
For the normal case where the call back into the PCM core is via prepare_output_urb() the "_under_stream_lock" variant of snd_pcm_period_elapsed() is called, but when an error occurs and the stream is stopped as XRUN then snd_pcm_xrun() tries to recursively lock the stream which results in deadlock.
Follow the example of snd_pcm_period_elapsed() by adding snd_pcm_xrun_under_stream_lock() and use this when the PCM substream lock is already held.
Signed-off-by: John Keeping john@metanate.com --- include/sound/pcm.h | 1 + sound/core/pcm_native.c | 28 ++++++++++++++++++++++++---- sound/usb/endpoint.c | 18 +++++++++++------- 3 files changed, 36 insertions(+), 11 deletions(-)
diff --git a/include/sound/pcm.h b/include/sound/pcm.h index 27040b472a4f..98551907453a 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -571,6 +571,7 @@ int snd_pcm_status64(struct snd_pcm_substream *substream, int snd_pcm_start(struct snd_pcm_substream *substream); int snd_pcm_stop(struct snd_pcm_substream *substream, snd_pcm_state_t status); int snd_pcm_drain_done(struct snd_pcm_substream *substream); +int snd_pcm_stop_xrun_under_stream_lock(struct snd_pcm_substream *substream); int snd_pcm_stop_xrun(struct snd_pcm_substream *substream); #ifdef CONFIG_PM int snd_pcm_suspend_all(struct snd_pcm *pcm); diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 331380c2438b..617f5dc74df0 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -1559,24 +1559,44 @@ int snd_pcm_drain_done(struct snd_pcm_substream *substream) SNDRV_PCM_STATE_SETUP); }
+/** + * snd_pcm_stop_xrun_under_stream_lock - stop the running stream as XRUN under the lock of + * the PCM substream. + * @substream: the PCM substream instance + * + * This stops the given running substream (and all linked substreams) as XRUN. + * This function assumes that the substream lock is already held. + * + * Return: Zero if successful, or a negative error core. + */ +int snd_pcm_stop_xrun_under_stream_lock(struct snd_pcm_substream *substream) +{ + if (substream->runtime && snd_pcm_running(substream)) + __snd_pcm_xrun(substream); + + return 0; +} + /** * snd_pcm_stop_xrun - stop the running streams as XRUN * @substream: the PCM substream instance * + * This function is similar to ``snd_pcm_stop_xrun_under_stream_lock()`` except that it + * acquires the substream lock itself. + * * This stops the given running substream (and all linked substreams) as XRUN. - * Unlike snd_pcm_stop(), this function takes the substream lock by itself. * * Return: Zero if successful, or a negative error code. */ int snd_pcm_stop_xrun(struct snd_pcm_substream *substream) { unsigned long flags; + int ret;
snd_pcm_stream_lock_irqsave(substream, flags); - if (substream->runtime && snd_pcm_running(substream)) - __snd_pcm_xrun(substream); + ret = snd_pcm_stop_xrun_under_stream_lock(substream); snd_pcm_stream_unlock_irqrestore(substream, flags); - return 0; + return ret; } EXPORT_SYMBOL_GPL(snd_pcm_stop_xrun);
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 1e0af1179ca8..83a6b6d41374 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -400,13 +400,17 @@ static int prepare_inbound_urb(struct snd_usb_endpoint *ep, }
/* notify an error as XRUN to the assigned PCM data substream */ -static void notify_xrun(struct snd_usb_endpoint *ep) +static void notify_xrun(struct snd_usb_endpoint *ep, bool in_stream_lock) { struct snd_usb_substream *data_subs;
data_subs = READ_ONCE(ep->data_subs); - if (data_subs && data_subs->pcm_substream) - snd_pcm_stop_xrun(data_subs->pcm_substream); + if (data_subs && data_subs->pcm_substream) { + if (in_stream_lock) + snd_pcm_stop_xrun_under_stream_lock(data_subs->pcm_substream); + else + snd_pcm_stop_xrun(data_subs->pcm_substream); + } }
static struct snd_usb_packet_info * @@ -498,7 +502,7 @@ void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, if (err == -EAGAIN) push_back_to_ready_list(ep, ctx); else - notify_xrun(ep); + notify_xrun(ep, in_stream_lock); return; }
@@ -507,7 +511,7 @@ void snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep, usb_audio_err(ep->chip, "Unable to submit urb #%d: %d at %s\n", ctx->index, err, __func__); - notify_xrun(ep); + notify_xrun(ep, in_stream_lock); return; }
@@ -574,7 +578,7 @@ static void snd_complete_urb(struct urb *urb) return;
usb_audio_err(ep->chip, "cannot submit urb (err = %d)\n", err); - notify_xrun(ep); + notify_xrun(ep, false);
exit_clear: clear_bit(ctx->index, &ep->active_mask); @@ -1762,7 +1766,7 @@ static void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep, usb_audio_err(ep->chip, "next package FIFO overflow EP 0x%x\n", ep->ep_num); - notify_xrun(ep); + notify_xrun(ep, false); return; }