rework memory block management to be thread-safe and mostly lock-free.

pa_memblock is now an opaque structure. Access to its fields is now done
through various accessor functions in a thread-safe manner.

pa_memblock_acquire() and pa_memblock_release() are now used to access the
attached audio data. Why? To allow safe manipulation of the memory pointer
maintained by the memory block. Internally _acquire() and _release() maintain a
reference counter. Please do not confuse this reference counter whith the one
maintained by pa_memblock_ref()/_unref()!

As a side effect this patch removes all direct usages of AO_t and replaces it
with pa_atomic_xxx based code.

This stuff needs some serious testing love. Especially if threads are actively
used.



git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@1404 fefdeb5f-60dc-0310-8127-8f9354f1896f

1 files changed, 12 insertions, 2 deletions

diff --git a/src/modules/module-alsa-sink.c b/src/modules/module-alsa-sink.c
index 6ff9a6e4..7bbd7de2 100644
--- a/src/modules/module-alsa-sink.c
+++ b/src/modules/module-alsa-sink.c
@@ -144,6 +144,7 @@ static void do_write(struct userdata *u) {
     update_usage(u);
     
     for (;;) {
+        void *p;
         pa_memchunk *memchunk = NULL;
         snd_pcm_sframes_t frames;
         
@@ -156,9 +157,15 @@ static void do_write(struct userdata *u) {
                 memchunk = &u->memchunk;
         }
             
-        assert(memchunk->memblock && memchunk->memblock->data && memchunk->length && memchunk->memblock->length && (memchunk->length % u->frame_size) == 0);
+        assert(memchunk->memblock);
+        assert(memchunk->length);
+        assert((memchunk->length % u->frame_size) == 0);
 
-        if ((frames = snd_pcm_writei(u->pcm_handle, (uint8_t*) memchunk->memblock->data + memchunk->index, memchunk->length / u->frame_size)) < 0) {
+        p = pa_memblock_acquire(memchunk->memblock);
+        
+        if ((frames = snd_pcm_writei(u->pcm_handle, (uint8_t*) p + memchunk->index, memchunk->length / u->frame_size)) < 0) {
+            pa_memblock_release(memchunk->memblock);
+            
             if (frames == -EAGAIN)
                 return;
 
@@ -176,6 +183,9 @@ static void do_write(struct userdata *u) {
             return;
         }
 
+        pa_memblock_release(memchunk->memblock);
+        
+
         if (memchunk == &u->memchunk) {
             size_t l = frames * u->frame_size;
             memchunk->index += l;