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

2 files changed, 17 insertions, 4 deletions

diff --git a/src/pulse/internal.h b/src/pulse/internal.h
index 4eef4b4a..76d80d83 100644
--- a/src/pulse/internal.h
+++ b/src/pulse/internal.h
@@ -113,6 +113,7 @@ struct pa_stream {
     uint32_t requested_bytes;
 
     pa_memchunk peek_memchunk;
+    void *peek_data;
     pa_memblockq *record_memblockq;
 
     int corked;
diff --git a/src/pulse/stream.c b/src/pulse/stream.c
index 180cd096..d31127d8 100644
--- a/src/pulse/stream.c
+++ b/src/pulse/stream.c
@@ -88,6 +88,7 @@ pa_stream *pa_stream_new(pa_context *c, const char *name, const pa_sample_spec *
     s->peek_memchunk.index = 0;
     s->peek_memchunk.length = 0;
     s->peek_memchunk.memblock = NULL;
+    s->peek_data = NULL;
 
     s->record_memblockq = NULL;
 
@@ -122,8 +123,11 @@ static void stream_free(pa_stream *s) {
         s->mainloop->time_free(s->auto_timing_update_event);
     }
 
-    if (s->peek_memchunk.memblock)
+    if (s->peek_memchunk.memblock) {
+        if (s->peek_data)
+            pa_memblock_release(s->peek_memchunk.memblock);
         pa_memblock_unref(s->peek_memchunk.memblock);
+    }
 
     if (s->record_memblockq)
         pa_memblockq_free(s->record_memblockq);
@@ -605,8 +609,11 @@ int pa_stream_write(
     if (free_cb) 
         chunk.memblock = pa_memblock_new_user(s->context->mempool, (void*) data, length, free_cb, 1);
     else {
+        void *tdata;
         chunk.memblock = pa_memblock_new(s->context->mempool, length);
-        memcpy(chunk.memblock->data, data, length);
+        tdata = pa_memblock_acquire(chunk.memblock);
+        memcpy(tdata, data, length);
+        pa_memblock_release(chunk.memblock);
     }
         
     chunk.index = 0;
@@ -672,9 +679,12 @@ int pa_stream_peek(pa_stream *s, const void **data, size_t *length) {
             *length = 0;
             return 0;
         }
+
+        s->peek_data = pa_memblock_acquire(s->peek_memchunk.memblock);
     }
 
-    *data = (const char*) s->peek_memchunk.memblock->data + s->peek_memchunk.index;
+    assert(s->peek_data);
+    *data = (uint8_t*) s->peek_data + s->peek_memchunk.index;
     *length = s->peek_memchunk.length;
     return 0;
 }
@@ -692,7 +702,9 @@ int pa_stream_drop(pa_stream *s) {
     /* Fix the simulated local read index */
     if (s->timing_info_valid && !s->timing_info.read_index_corrupt)
         s->timing_info.read_index += s->peek_memchunk.length;
-    
+
+    assert(s->peek_data);
+    pa_memblock_release(s->peek_memchunk.memblock);
     pa_memblock_unref(s->peek_memchunk.memblock);
     s->peek_memchunk.length = 0;
     s->peek_memchunk.index = 0;