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67a7b5a993
The root cause is that alsa-lib is not thread safe for the same handle. There are two threads in the gstreamer accessing alsa-lib not serilized. The race condition happens when one thread holds the old framebuffer app_ptr position in the kernel, another thread advances the framebuffer app_ptr. when the former thread is scheduled to run again, it overwrites the app_ptr to old value by copying from kernel.Thus,the app_ptr in the upper alsa-lib(pcm_rate) become one period size more advanced than the lower alsa-lib(pcm_hw & kernel). gstreamer uses noblock and poll method to communicate with the alsa-lib. The app_ptr unsync situation as described above makes the poll return immediately because it concludes there is enough space for the ring-buffer via the low-level alsa-lib. The write function returns immediately because it concludes there is not enough space for the ring-buffer from the upper-level alsa-lib. Then the loop of poll and write runs again and again until another period size is available for ring-buffer.This leads to the cpu 100 problem. delay_lock is used to avoid the race condition. Fixes: https://bugzilla.gnome.org/show_bug.cgi?id=690937
91 lines
2.7 KiB
C
91 lines
2.7 KiB
C
/* GStreamer
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* Copyright (C) 2005 Wim Taymans <wim@fluendo.com>
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*
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* gstalsasink.h:
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef __GST_ALSASINK_H__
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#define __GST_ALSASINK_H__
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#include <gst/gst.h>
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#include <gst/audio/audio.h>
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#include <alsa/asoundlib.h>
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G_BEGIN_DECLS
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#define GST_TYPE_ALSA_SINK (gst_alsasink_get_type())
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#define GST_ALSA_SINK(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_ALSA_SINK,GstAlsaSink))
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#define GST_ALSA_SINK_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_ALSA_SINK,GstAlsaSinkClass))
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#define GST_IS_ALSA_SINK(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_ALSA_SINK))
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#define GST_IS_ALSA_SINK_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_ALSA_SINK))
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#define GST_ALSA_SINK_CAST(obj) ((GstAlsaSink *) (obj))
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typedef struct _GstAlsaSink GstAlsaSink;
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typedef struct _GstAlsaSinkClass GstAlsaSinkClass;
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#define GST_ALSA_SINK_GET_LOCK(obj) (&GST_ALSA_SINK_CAST (obj)->alsa_lock)
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#define GST_ALSA_SINK_LOCK(obj) (g_mutex_lock (GST_ALSA_SINK_GET_LOCK (obj)))
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#define GST_ALSA_SINK_UNLOCK(obj) (g_mutex_unlock (GST_ALSA_SINK_GET_LOCK (obj)))
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#define GST_DELAY_SINK_GET_LOCK(obj) (&GST_ALSA_SINK_CAST (obj)->delay_lock)
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#define GST_DELAY_SINK_LOCK(obj) (g_mutex_lock (GST_DELAY_SINK_GET_LOCK (obj)))
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#define GST_DELAY_SINK_UNLOCK(obj) (g_mutex_unlock (GST_DELAY_SINK_GET_LOCK (obj)))
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/**
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* GstAlsaSink:
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*
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* Opaque data structure
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*/
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struct _GstAlsaSink {
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GstAudioSink sink;
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gchar *device;
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snd_pcm_t *handle;
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snd_pcm_hw_params_t *hwparams;
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snd_pcm_sw_params_t *swparams;
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snd_pcm_access_t access;
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snd_pcm_format_t format;
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guint rate;
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guint channels;
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gint bpf;
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gboolean iec958;
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gboolean need_swap;
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guint buffer_time;
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guint period_time;
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snd_pcm_uframes_t buffer_size;
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snd_pcm_uframes_t period_size;
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GstCaps *cached_caps;
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GMutex alsa_lock;
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GMutex delay_lock;
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};
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struct _GstAlsaSinkClass {
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GstAudioSinkClass parent_class;
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};
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GType gst_alsasink_get_type(void);
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G_END_DECLS
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#endif /* __GST_ALSASINK_H__ */
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