92 lines
3.5 KiB
Diff
92 lines
3.5 KiB
Diff
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From 67a7b5a99317ca1f92fb6a88542647aa3ad92c4b Mon Sep 17 00:00:00 2001
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From: yanghuolin <Huolin.Yang@delphi.com>
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Date: Thu, 15 Nov 2012 08:31:47 +0000
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Subject: alsasink: don't use 100% CPU
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The root cause is that alsa-lib is not thread safe for the same handle.
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There are two threads in the gstreamer accessing alsa-lib not serilized.
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The race condition happens when one thread holds the old framebuffer app_ptr
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position in the kernel, another thread advances the framebuffer app_ptr.
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when the former thread is scheduled to run again, it overwrites the app_ptr
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to old value by copying from kernel.Thus,the app_ptr in the upper
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alsa-lib(pcm_rate) become one period size more advanced than the lower
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alsa-lib(pcm_hw & kernel).
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gstreamer uses noblock and poll method to communicate with the alsa-lib.
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The app_ptr unsync situation as described above makes the poll return immediately because
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it concludes there is enough space for the ring-buffer via the low-level alsa-lib.
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The write function returns immediately because it concludes there is not enough
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space for the ring-buffer from the upper-level alsa-lib. Then the loop of poll
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and write runs again and again until another period size is available for
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ring-buffer.This leads to the cpu 100 problem.
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delay_lock is used to avoid the race condition.
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Fixes: https://bugzilla.gnome.org/show_bug.cgi?id=690937
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---
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diff --git a/ext/alsa/gstalsasink.c b/ext/alsa/gstalsasink.c
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index 1ef6b91..81731b6 100644
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--- a/ext/alsa/gstalsasink.c
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+++ b/ext/alsa/gstalsasink.c
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@@ -118,6 +118,7 @@ gst_alsasink_finalise (GObject * object)
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g_free (sink->device);
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g_mutex_clear (&sink->alsa_lock);
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+ g_mutex_clear (&sink->delay_lock);
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g_mutex_lock (&output_mutex);
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--output_ref;
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@@ -255,6 +256,7 @@ gst_alsasink_init (GstAlsaSink * alsasink)
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alsasink->handle = NULL;
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alsasink->cached_caps = NULL;
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g_mutex_init (&alsasink->alsa_lock);
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+ g_mutex_init (&alsasink->delay_lock);
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g_mutex_lock (&output_mutex);
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if (output_ref == 0) {
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@@ -1011,7 +1013,9 @@ gst_alsasink_write (GstAudioSink * asink, gpointer data, guint length)
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if (err < 0) {
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GST_DEBUG_OBJECT (asink, "wait error, %d", err);
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} else {
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+ GST_DELAY_SINK_LOCK (asink);
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err = snd_pcm_writei (alsa->handle, ptr, cptr);
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+ GST_DELAY_SINK_UNLOCK (asink);
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}
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GST_DEBUG_OBJECT (asink, "written %d frames out of %d", err, cptr);
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@@ -1057,7 +1061,9 @@ gst_alsasink_delay (GstAudioSink * asink)
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alsa = GST_ALSA_SINK (asink);
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+ GST_DELAY_SINK_LOCK (asink);
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res = snd_pcm_delay (alsa->handle, &delay);
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+ GST_DELAY_SINK_UNLOCK (asink);
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if (G_UNLIKELY (res < 0)) {
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/* on errors, report 0 delay */
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GST_DEBUG_OBJECT (alsa, "snd_pcm_delay returned %d", res);
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diff --git a/ext/alsa/gstalsasink.h b/ext/alsa/gstalsasink.h
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index 3a64a92..8c4c1b0 100644
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--- a/ext/alsa/gstalsasink.h
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+++ b/ext/alsa/gstalsasink.h
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@@ -43,6 +43,10 @@ typedef struct _GstAlsaSinkClass GstAlsaSinkClass;
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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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/**
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* GstAlsaSink:
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*
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@@ -73,6 +77,7 @@ struct _GstAlsaSink {
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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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--
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cgit v0.9.0.2-2-gbebe
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