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, 7 insertions, 3 deletions

diff --git a/src/modules/module-alsa-source.c b/src/modules/module-alsa-source.c
index aa0666f1..9bde46da 100644
--- a/src/modules/module-alsa-source.c
+++ b/src/modules/module-alsa-source.c
@@ -149,6 +149,7 @@ static void do_read(struct userdata *u) {
         pa_memchunk post_memchunk;
         snd_pcm_sframes_t frames;
         size_t l;
+        void *p;
         
         if (!u->memchunk.memblock) {
             u->memchunk.memblock = pa_memblock_new(u->source->core->mempool, u->memchunk.length = u->fragment_size);
@@ -157,11 +158,13 @@ static void do_read(struct userdata *u) {
             
         assert(u->memchunk.memblock);
         assert(u->memchunk.length);
-        assert(u->memchunk.memblock->data);
-        assert(u->memchunk.memblock->length);
         assert(u->memchunk.length % u->frame_size == 0);
 
-        if ((frames = snd_pcm_readi(u->pcm_handle, (uint8_t*) u->memchunk.memblock->data + u->memchunk.index, u->memchunk.length / u->frame_size)) < 0) {
+        p = pa_memblock_acquire(u->memchunk.memblock);
+        
+        if ((frames = snd_pcm_readi(u->pcm_handle, (uint8_t*) p + u->memchunk.index, u->memchunk.length / u->frame_size)) < 0) {
+            pa_memblock_release(u->memchunk.memblock);
+            
             if (frames == -EAGAIN)
                 return;
             
@@ -178,6 +181,7 @@ static void do_read(struct userdata *u) {
             pa_module_unload_request(u->module);
             return;
         }
+        pa_memblock_release(u->memchunk.memblock);
 
         l = frames * u->frame_size;