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, 15 insertions, 7 deletions

diff --git a/src/modules/module-oss.c b/src/modules/module-oss.c
index b71581d9..73f0d57e 100644
--- a/src/modules/module-oss.c
+++ b/src/modules/module-oss.c
@@ -155,6 +155,7 @@ static void do_write(struct userdata *u) {
     }
 
     do {
+        void *p;
         memchunk = &u->memchunk;
         
         if (!memchunk->length)
@@ -162,16 +163,18 @@ static void do_write(struct userdata *u) {
                 memchunk = &u->silence;
         
         assert(memchunk->memblock);
-        assert(memchunk->memblock->data);
         assert(memchunk->length);
-        
-        if ((r = pa_iochannel_write(u->io, (uint8_t*) memchunk->memblock->data + memchunk->index, memchunk->length)) < 0) {
+
+        p = pa_memblock_acquire(memchunk->memblock);
+        if ((r = pa_iochannel_write(u->io, (uint8_t*) p + memchunk->index, memchunk->length)) < 0) {
+            pa_memblock_release(memchunk->memblock);
             pa_log("write() failed: %s", pa_cstrerror(errno));
 
             clear_up(u);
             pa_module_unload_request(u->module);
             break;
         }
+        pa_memblock_release(memchunk->memblock);
         
         if (memchunk == &u->silence)
             assert(r % u->sample_size == 0);
@@ -217,9 +220,13 @@ static void do_read(struct userdata *u) {
     }
     
     do {
+        void *p;
         memchunk.memblock = pa_memblock_new(u->core->mempool, l);
-        assert(memchunk.memblock);
-        if ((r = pa_iochannel_read(u->io, memchunk.memblock->data, memchunk.memblock->length)) < 0) {
+
+        p = pa_memblock_acquire(memchunk.memblock);
+        
+        if ((r = pa_iochannel_read(u->io, p, pa_memblock_get_length(memchunk.memblock))) < 0) {
+            pa_memblock_release(memchunk.memblock);
             pa_memblock_unref(memchunk.memblock);
             if (errno != EAGAIN) {
                 pa_log("read() failed: %s", pa_cstrerror(errno));
@@ -228,9 +235,10 @@ static void do_read(struct userdata *u) {
             }
             break;
         }
+        pa_memblock_release(memchunk.memblock);
         
-        assert(r <= (ssize_t) memchunk.memblock->length);
-        memchunk.length = memchunk.memblock->length = r;
+        assert(r <= (ssize_t) pa_memblock_get_length(memchunk.memblock));
+        memchunk.length = r;
         memchunk.index = 0;
         
         pa_source_post(u->source, &memchunk);