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The recent support of low latency playback in USB-audio driver made
the snd_usb_queue_pending_output_urbs() function to be called via PCM
ack ops. In the new code path, the function is performed already in
the PCM stream lock. The problem is that, when an XRUN is detected,
the function calls snd_pcm_xrun() to notify, but snd_pcm_xrun() is
supposed to be called only outside the stream lock. As a result, it
leads to a deadlock of PCM stream locking.
For avoiding such a recursive locking, this patch adds an additional
check to the code paths in PCM core that call the ack callback; now it
checks the error code from the callback, and if it's -EPIPE, the XRUN
is handled in the PCM core side gracefully. Along with it, the
USB-audio driver code is changed to follow that, i.e. -EPIPE is
returned instead of the explicit snd_pcm_xrun() call when the function
is performed already in the stream lock.
Fixes: d5f871f89e ("ALSA: usb-audio: Improved lowlatency playback support")
Reported-and-tested-by: John Keeping <john@metanate.com>
Link: https://lore.kernel.org/r/20230317195128.3911155-1-john@metanate.com
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Reviewed-by; Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230320142838.494-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
59 lines
2.3 KiB
C
59 lines
2.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __USBAUDIO_ENDPOINT_H
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#define __USBAUDIO_ENDPOINT_H
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#define SND_USB_ENDPOINT_TYPE_DATA 0
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#define SND_USB_ENDPOINT_TYPE_SYNC 1
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struct snd_usb_endpoint *snd_usb_get_endpoint(struct snd_usb_audio *chip,
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int ep_num);
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int snd_usb_add_endpoint(struct snd_usb_audio *chip, int ep_num, int type);
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struct snd_usb_endpoint *
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snd_usb_endpoint_open(struct snd_usb_audio *chip,
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const struct audioformat *fp,
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const struct snd_pcm_hw_params *params,
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bool is_sync_ep,
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bool fixed_rate);
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void snd_usb_endpoint_close(struct snd_usb_audio *chip,
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struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_set_params(struct snd_usb_audio *chip,
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struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_prepare(struct snd_usb_audio *chip,
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struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_get_clock_rate(struct snd_usb_audio *chip, int clock);
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bool snd_usb_endpoint_compatible(struct snd_usb_audio *chip,
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struct snd_usb_endpoint *ep,
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const struct audioformat *fp,
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const struct snd_pcm_hw_params *params);
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void snd_usb_endpoint_set_sync(struct snd_usb_audio *chip,
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struct snd_usb_endpoint *data_ep,
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struct snd_usb_endpoint *sync_ep);
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void snd_usb_endpoint_set_callback(struct snd_usb_endpoint *ep,
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int (*prepare)(struct snd_usb_substream *subs,
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struct urb *urb,
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bool in_stream_lock),
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void (*retire)(struct snd_usb_substream *subs,
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struct urb *urb),
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struct snd_usb_substream *data_subs);
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int snd_usb_endpoint_start(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep, bool keep_pending);
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void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_suspend(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_release(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_free_all(struct snd_usb_audio *chip);
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int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep,
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struct snd_urb_ctx *ctx, int idx,
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unsigned int avail);
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int snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep,
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bool in_stream_lock);
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#endif /* __USBAUDIO_ENDPOINT_H */
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