Fix stdin handling in CUFileDriverScope

- adds stdin backup and restore mechanism to prevent issues with file descriptor
  handling when using cuFile library. This fixes a problem where cuFileDriverOpen
  could close stdin, causing subsequent GDS file operations to fail when the file
  descriptor 0 is reused.

Signed-off-by: Janusz Lisiecki <[email protected]>

Author: JanuszL

dali/operators/reader/gds_mem_test.cu

@@ -32,7 +32,23 @@ namespace test {
 
 struct CUFileDriverScope {
   CUFileDriverScope() {
+    // cuFileDriverOpen is some versions of cuFile library, can close stdin
+    // returning 0 file descriptor to the pool, then dali gets it from the OS opening a file
+    // and passing to GDS which cannot handle it properly leading to an error
+    int stdin_backup = dup(STDIN_FILENO);
+    if (stdin_backup == -1) {
+      std::cerr << "dup failed: " << strerror(errno) << "\n";
+    }
     CUDA_CALL(cuFileDriverOpen());
+    if (stdin_backup != -1) {
+      if (fcntl(STDIN_FILENO, F_GETFL) == -1 && errno == EBADF) {
+        // Restore stdin from backup
+        if (dup2(stdin_backup, STDIN_FILENO) == -1) {
+          std::cerr << "dup2 failed: " << strerror(errno) << "\n";
+        }
+      }
+      close(stdin_backup);  // Cleanup backup
+    }
   }
   ~CUFileDriverScope() {
     // Here we're the sole owner of cuFile library - we can (and want to) call cuFileDriverClose

dali/util/cufile_helper.h

@@ -37,7 +37,23 @@ struct CUFileDriverScope {
   CUFileDriverScope() {
     // v2 API performs proper reference counting, so we increase the reference count here...
     if (cuFileIsSymbolAvailable("cuFileDriverClose_v2")) {
+      // cuFileDriverOpen is some versions of cuFile library, can close stdin
+      // returning 0 file descriptor to the pool, then dali gets it from the OS opening a file
+      // and passing to GDS which cannot handle it properly leading to an error
+      int stdin_backup = dup(STDIN_FILENO);
+      if (stdin_backup == -1) {
+        std::cerr << "dup failed: " << strerror(errno) << "\n";
+      }
       CUDA_CALL(cuFileDriverOpen());
+      if (stdin_backup != -1) {
+        if (fcntl(STDIN_FILENO, F_GETFL) == -1 && errno == EBADF) {
+          // Restore stdin from backup
+          if (dup2(stdin_backup, STDIN_FILENO) == -1) {
+            std::cerr << "dup2 failed: " << strerror(errno) << "\n";
+          }
+        }
+        close(stdin_backup);  // Cleanup backup
+      }
     }
   }
   ~CUFileDriverScope() {