[src] Fix for threaded nnet2 decoding: check if threads are joinable before calling join(), to avoid multiple calls to join() (#1725)

Author: alumae

src/online2/online-nnet2-decoding-threaded.cc

@@ -374,8 +374,10 @@ void SingleUtteranceNnet2DecoderThreaded::RunDecoderSearch(
 
 
 void SingleUtteranceNnet2DecoderThreaded::WaitForAllThreads() {
- for (int32 i = 0; i < 2; i++) // there are 2 spawned threads.
- threads_[i].join();
+ for (int32 i = 0; i < 2; i++) { // there are 2 spawned threads.
+ if (threads_[i].joinable())
+ threads_[i].join();
+ }
  if (error_)
  KALDI_ERR << "Error encountered during decoding. See above.";
 }