pcm: dmix_rewind corrupts application pointer fix

sometimes pulseaudio stops with the following assertion in libasound.so:
alsa-lib-1.0.29/src/pcm/pcm.c:2761:
snd_pcm_area_copy: Assertion `dst < src || dst >= src + bytes' failed.
Application pointer is handled properly, in cases of rewind operations.

Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>
Signed-off-by: Ravikiran Polepalli <ravikiran_polepalli@mentor.com>
Signed-off-by: Mikhail Durnev <mikhail_durnev@mentor.com>
Signed-off-by: Mounesh Sutar <sutar.mounesh@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index dd0356e..46142e5 100644 (file)
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -706,7 +706,7 @@ static snd_pcm_sframes_t snd_pcm_dmix_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t f
 {
        snd_pcm_direct_t *dmix = pcm->private_data;
        snd_pcm_uframes_t slave_appl_ptr, slave_size;
-       snd_pcm_uframes_t appl_ptr, size, transfer, result;
+       snd_pcm_uframes_t appl_ptr, size, transfer, result, frames_to_remix;
        int err;
        const snd_pcm_channel_area_t *src_areas, *dst_areas;
 
@@ -717,6 +717,13 @@ static snd_pcm_sframes_t snd_pcm_dmix_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t f
                        return err;
        }
 
+       /* (appl_ptr - last_appl_ptr) indicates the frames which are not
+        * already mixed
+        * (last_appl_ptr - hw_ptr)  indicates the frames which are already
+        * mixed but not played yet.
+        * So they can be remixed.
+        */
+
        if (dmix->last_appl_ptr < dmix->appl_ptr)
                size = dmix->appl_ptr - dmix->last_appl_ptr;
        else
@@ -729,6 +736,9 @@ static snd_pcm_sframes_t snd_pcm_dmix_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t f
                return size;
        result = size;
 
+       /* Always at this point last_appl_ptr == appl_ptr
+        * So (appl_ptr - hw_ptr) indicates the frames which can be remixed
+        */
        if (dmix->hw_ptr < dmix->appl_ptr)
                size = dmix->appl_ptr - dmix->hw_ptr;
        else
@@ -741,9 +751,12 @@ static snd_pcm_sframes_t snd_pcm_dmix_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t f
                slave_size = dmix->slave_appl_ptr + (pcm->boundary - dmix->slave_hw_ptr);
        if (slave_size < size)
                size = slave_size;
-       frames -= size;
-       result += size;
-               
+
+       /* frames which should be remixed will be saved
+        * to also backward the appl pointer on success
+        */
+       frames_to_remix = size;
+
        /* add sample areas here */
        src_areas = snd_pcm_mmap_areas(pcm);
        dst_areas = snd_pcm_mmap_areas(dmix->spcm);
@@ -769,15 +782,15 @@ static snd_pcm_sframes_t snd_pcm_dmix_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t f
                appl_ptr += transfer;
                appl_ptr %= pcm->buffer_size;
        }
-       dmix->last_appl_ptr -= frames;
-       dmix->last_appl_ptr %= pcm->boundary;
-       dmix->slave_appl_ptr -= frames;
-       dmix->slave_appl_ptr %= dmix->slave_boundary;
        dmix_up_sem(dmix);
 
-       snd_pcm_mmap_appl_backward(pcm, frames);
+       snd_pcm_mmap_appl_backward(pcm, frames_to_remix);
+       result += frames_to_remix;
+       /* At this point last_appl_ptr and appl_ptr has to indicate the
+        * position of the first not mixed frame
+        */
 
-       return result + frames;
+       return result;
 }
 
 static snd_pcm_sframes_t snd_pcm_dmix_forwardable(snd_pcm_t *pcm)