Fixing the WZ DMA initialization / teardown

We are getting SEGFAULTs after WZ_DMA cannot allocate memory because of uninitialized variables. Fixing.

src/WZDmaInputFilter.cc

@@ -18,6 +18,7 @@ WZDmaInputFilter::WZDmaInputFilter(size_t packetBufferSize,
       sconeHost_ {conf.getSconeHost()}, sconePort_ {conf.getSconePort()},
       sconeBoard_ {conf.getSconeBoard()} {
   // Initialize the DMA subsystem
+  dma_is_initialized_ = false;
   if (wz_init(&dma_) < 0) {
     std::string msg = "Cannot initialize WZ DMA device";
     if (errno == ENOENT) {
@@ -27,6 +28,7 @@ WZDmaInputFilter::WZDmaInputFilter(size_t packetBufferSize,
     }
     throw std::system_error(errno, std::system_category(), msg);
   }
+  dma_is_initialized_ = true;
 
   // Start the DMA
   if (wz_start_dma(&dma_) < 0) {
@@ -38,8 +40,11 @@ WZDmaInputFilter::WZDmaInputFilter(size_t packetBufferSize,
 }
 
 WZDmaInputFilter::~WZDmaInputFilter() {
-  wz_stop_dma(&dma_);
-  wz_close(&dma_);
+  if (dma_is_initialized_) {
+    wz_stop_dma(&dma_);
+    wz_close(&dma_);
+    dma_is_initialized_ = false;
+  }
   LOG(TRACE) << "Destroyed WZ DMA input filter";
 }
 
@@ -51,22 +56,25 @@ inline ssize_t WZDmaInputFilter::read_packet_from_dma(char **buffer) {
     bytes_read = wz_read_start(&dma_, buffer);
 
     if (bytes_read < 0) {
+      int errno_saved = errno;
       stats.nbDmaErrors++;
       LOG(ERROR) << tools::strerror(
           "#" + std::to_string(nbReads()) +
-          ": Read failed, returned: " + std::to_string(bytes_read));
+          ": Read failed, returned: " + std::to_string(bytes_read)) << ", errno: " << errno_saved;
 
-      if (errno == EIO) {
+      if (errno_saved == EIO) {
         LOG(ERROR) << "#" << nbReads() << ": Trying to restart DMA (attempt #"
                    << tries << "):";
         wz_stop_dma(&dma_);
         wz_close(&dma_);
+        dma_is_initialized_ = false;
 
         // Initialize the DMA subsystem
         if (wz_init(&dma_) < 0) {
           throw std::system_error(errno, std::system_category(),
                                   "Cannot initialize WZ DMA device");
         }
+        dma_is_initialized_ = true;
 
         if (wz_start_dma(&dma_) < 0) {
           throw std::system_error(errno, std::system_category(),
@@ -81,7 +89,7 @@ inline ssize_t WZDmaInputFilter::read_packet_from_dma(char **buffer) {
         }
         continue;
       }
-      throw std::system_error(errno, std::system_category(),
+      throw std::system_error(errno_saved, std::system_category(),
                               "FATAL: Unrecoverable DMA error detected.");
     }
     break;