On Tue, 9 Oct 2001, Kai Vehmanen wrote:
> You have /dev/dsp opened for playback. Then:
>
> int enable_bits = ~PCM_ENABLE_OUTPUT; /* disables playback */
> ioctl(audio_fd, SNDCTL_DSP_SETTRIGGER, &enable_bits) == -1)
>
> ... next you start writing data to the device, but forget to ever issue
> the actual trigger call (ie.
>
> int enable_bits = PCM_ENABLE_OUTPUT;
> ioctl(audio_fd, SNDCTL_DSP_SETTRIGGER, &enable_bits);
>
> ). Now this causes a more-or-less complete system-freeze (SMP, user
> priviledges). The latest ecasound development version (2.1dev0) failed to
> ever start the audio device and thus triggered this bug. It took quite a
> while to trace down the problem. Finally S.Massy was able to pinpoint the
> problem to oss-emulation, and problem was resolved.
>
> Of course, this is really an application side problem (fixed in ecasound
> 2.1dev1 btw), but it might make sense to add a safety-bealt to the
> oss-emulation. OSS/comm drivers survived the buggy ecasound. Also ALSA's
> native pcm-interface survived (SND_PCM_START_EXPLICIT set, after buffer
> became full without an snd_pcm_start(), snd_pcm_writei() returned an
> error).
Thanks for this bug report. The following patch (already applied to CVS)
should fix this problem:
Index: pcm_oss.c
===================================================================
RCS file: /cvsroot/alsa/alsa-driver/kernel/oss/pcm_oss.c,v
retrieving revision 1.101
diff -u -r1.101 pcm_oss.c
--- pcm_oss.c 2001/10/09 14:47:28 1.101
+++ pcm_oss.c 2001/10/09 16:11:13
@@ -506,6 +506,10 @@
snd_leave_user(fs);
if (ret != -EPIPE && ret != -ESTRPIPE)
break;
+ /* test, if we can't store new data, because the stream */
+ /* has not been started */
+ if (runtime->status->state == SNDRV_PCM_STATE_PREPARED)
+ return -EAGAIN;
}
return ret;
}
@@ -556,6 +560,10 @@
snd_leave_user(fs);
if (ret != -EPIPE && ret != -ESTRPIPE)
break;
+ /* test, if we can't store new data, because the stream */
+ /* has not been started */
+ if (runtime->status->state == SNDRV_PCM_STATE_PREPARED)
+ return -EAGAIN;
}
return ret;
}
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
SuSE Linux http://www.suse.com
ALSA project http://www.alsa-project.org
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