[downloader/fragment] Fix problem where multiple threads can share one iterator

which causes "ValueError: generator already executing" error

Closes #2881

yt_dlp/downloader/fragment.py

@@ -410,17 +410,16 @@ class FragmentFD(FileDownloader):
             def bindoj_result(future):
                 return future.result()
 
-        spins = []
-        for idx, (ctx, fragments, info_dict) in enumerate(args):
-            tpe = FTPE(math.ceil(max_workers / max_progress))
-
-            def interrupt_trigger_iter():
-                for f in fragments:
+        def interrupt_trigger_iter(fg):
+            for f in fg:
                 if not interrupt_trigger[0]:
                     break
                 yield f
 
-            job = tpe.submit(thread_func, idx, ctx, interrupt_trigger_iter(), info_dict, tpe)
+        spins = []
+        for idx, (ctx, fragments, info_dict) in enumerate(args):
+            tpe = FTPE(math.ceil(max_workers / max_progress))
+            job = tpe.submit(thread_func, idx, ctx, interrupt_trigger_iter(fragments), info_dict, tpe)
             spins.append((tpe, job))
 
         result = True