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, 10 insertions, 3 deletions

diff --git a/src/modules/module-pipe-source.c b/src/modules/module-pipe-source.c
index c251f7ac..99f4f3b9 100644
--- a/src/modules/module-pipe-source.c
+++ b/src/modules/module-pipe-source.c
@@ -82,7 +82,9 @@ static const char* const valid_modargs[] = {
 
 static void do_read(struct userdata *u) {
     ssize_t r;
+    void *p;
     pa_memchunk chunk;
+    
     assert(u);
 
     if (!pa_iochannel_is_readable(u->io))
@@ -95,17 +97,22 @@ static void do_read(struct userdata *u) {
         u->chunk.index = chunk.length = 0;
     }
 
-    assert(u->chunk.memblock && u->chunk.memblock->length > u->chunk.index);
-    if ((r = pa_iochannel_read(u->io, (uint8_t*) u->chunk.memblock->data + u->chunk.index, u->chunk.memblock->length - u->chunk.index)) <= 0) {
+    assert(u->chunk.memblock);
+    assert(pa_memblock_get_length(u->chunk.memblock) > u->chunk.index);
+
+    p = pa_memblock_acquire(u->chunk.memblock);
+    if ((r = pa_iochannel_read(u->io, (uint8_t*) p + u->chunk.index, pa_memblock_get_length(u->chunk.memblock) - u->chunk.index)) <= 0) {
+        pa_memblock_release(u->chunk.memblock);
         pa_log("read(): %s", pa_cstrerror(errno));
         return;
     }
+    pa_memblock_release(u->chunk.memblock);
 
     u->chunk.length = r;
     pa_source_post(u->source, &u->chunk);
     u->chunk.index += r;
 
-    if (u->chunk.index >= u->chunk.memblock->length) {
+    if (u->chunk.index >= pa_memblock_get_length(u->chunk.memblock)) {
         u->chunk.index = u->chunk.length = 0;
         pa_memblock_unref(u->chunk.memblock);
         u->chunk.memblock = NULL;