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[ALSA] usb-audio: properly lock hwptr_done accesses

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USB generic driver
Take the substream lock when reading hwptr_done to avoid a race
condition with the updates in the URB callbacks.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
This commit is contained in:
Clemens Ladisch 2005-08-15 08:25:50 +02:00 committed by Jaroslav Kysela
parent 9624ea812c
commit daa150ef7d
1 changed files with 8 additions and 2 deletions
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10
sound/usb/usbaudio.c
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@ -815,8 +815,14 @@ static int wait_clear_urbs(snd_usb_substream_t *subs)
*/
static snd_pcm_uframes_t snd_usb_pcm_pointer(snd_pcm_substream_t *substream)
{
snd_usb_substream_t *subs = (snd_usb_substream_t *)substream->runtime->private_data;
return subs->hwptr_done;
snd_usb_substream_t *subs;
snd_pcm_uframes_t hwptr_done;
subs = (snd_usb_substream_t *)substream->runtime->private_data;
spin_lock(&subs->lock);
hwptr_done = subs->hwptr_done;
spin_unlock(&subs->lock);
return hwptr_done;
}