LV2 worker: prevent corruption of ringbuffer

git-svn-id: svn://localhost/ardour2/branches/3.0@13146 d708f5d6-7413-0410-9779-e7cbd77b26cf

diff --git a/libs/ardour/ardour/worker.h b/libs/ardour/ardour/worker.h
index cdc3d1d06d46be03014bd53b23e391b5190bb756..4f3ff54bc10782898d32a711e7826f246732cc29 100644 (file)
--- a/libs/ardour/ardour/worker.h
+++ b/libs/ardour/ardour/worker.h
@@ -75,6 +75,16 @@ public:
 
 private:
        void run();
+       /**
+          Peek in RB, get size and check if a block of 'size' is available.
+
+          Handle the unlikley edge-case, if we're called in between the
+          responder writing 'size' and 'data'.
+
+                @param rb the ringbuffer to check
+                @return true if the message is complete, false otherwise
+        */
+       bool verify_message_completeness(RingBuffer<uint8_t>* rb);
 
        Workee*                _workee;
        RingBuffer<uint8_t>*   _requests;
@@ -82,7 +92,8 @@ private:
        uint8_t*               _response;
        PBD::Semaphore         _sem;
        bool                   _exit;
-        Glib::Threads::Thread* _thread;
+       Glib::Threads::Thread* _thread;
+
 };
 
 } // namespace ARDOUR

diff --git a/libs/ardour/worker.cc b/libs/ardour/worker.cc
index 67c72ffeba0b4b290865d70022148a948e92e832..d48ac959ba5b80a00877e8778936ce7456c43a6f 100644 (file)
--- a/libs/ardour/worker.cc
+++ b/libs/ardour/worker.cc
@@ -44,11 +44,14 @@ Worker::~Worker()
 bool
 Worker::schedule(uint32_t size, const void* data)
 {
+       if (_requests->write_space() < size + sizeof(size)) {
+               return false;
+       }
        if (_requests->write((const uint8_t*)&size, sizeof(size)) != sizeof(size)) {
                return false;
        }
        if (_requests->write((const uint8_t*)data, size) != size) {
-               return false;  // FIXME: corruption
+               return false;
        }
        _sem.post();
        return true;
@@ -57,11 +60,34 @@ Worker::schedule(uint32_t size, const void* data)
 bool
 Worker::respond(uint32_t size, const void* data)
 {
+       if (_requests->write_space() < size + sizeof(size)) {
+               return false;
+       }
        if (_responses->write((const uint8_t*)&size, sizeof(size)) != sizeof(size)) {
                return false;
        }
        if (_responses->write((const uint8_t*)data, size) != size) {
-               return false;  // FIXME: corruption
+               return false;
+       }
+       return true;
+}
+
+bool
+Worker::verify_message_completeness(RingBuffer<uint8_t>* rb)
+{
+       uint32_t read_space = rb->read_space();
+       uint32_t size;
+       RingBuffer<uint8_t>::rw_vector vec;
+       rb->get_read_vector (&vec);
+       if (vec.len[0] >= sizeof(size)) {
+               memcpy (&size, vec.buf[0], sizeof (size));
+       } else {
+               memcpy (&size, vec.buf[0], vec.len[0]);
+               memcpy (&size + vec.len[0], vec.buf[1], sizeof(size) - vec.len[0]);
+       }
+       if (read_space < size+sizeof(size)) {
+               /* message from writer is yet incomplete. respond next cycle */
+               return false;
        }
        return true;
 }
@@ -71,7 +97,12 @@ Worker::emit_responses()
 {
        uint32_t read_space = _responses->read_space();
        uint32_t size       = 0;
-       while (read_space > sizeof(size)) {
+       while (read_space >= sizeof(size)) {
+               if (!verify_message_completeness(_responses)) {
+                       /* message from writer is yet incomplete. respond next cycle */
+                       return;
+               }
+               /* read and send response */
                _responses->read((uint8_t*)&size, sizeof(size));
                _responses->read(_response, size);
                _workee->work_response(size, _response);
@@ -90,7 +121,17 @@ Worker::run()
                        return;
                }
 
-               uint32_t size = 0;
+               uint32_t size = _requests->read_space();
+               if (size < sizeof(size)) {
+                       PBD::error << "Worker: no work-data on ring buffer" << endmsg;
+                       continue;
+               }
+               while (!verify_message_completeness(_requests)) {
+                       ::usleep(2000);
+                       if (_exit) {
+                               return;
+                       }
+               }
                if (_requests->read((uint8_t*)&size, sizeof(size)) < sizeof(size)) {
                        PBD::error << "Worker: Error reading size from request ring"
                                   << endmsg;