[Insight-users] FFTW thread safety

[Simon Rit]

Hi,
I have experienced problems with FFTW in ITK 4. I am doing many
parallel FFT filters, each parallel thread having the piece of the
image defined by ThreadedGenerateData. This is a filter part of
www.openrtk.org which code is here:
https://github.com/SimonRit/RTK/blob/master/code/rtkFFTRampImageFilter.txx

I have originally done that with the code of Gaëtan Lehmann
(http://www.insight-journal.org/browse/publication/717) but I had to
fix it then for thread safety. I have now moved to ITK4 but I think
that the thread safety issue is still here since I have random
crashes. The problem is that the destroy functions are not protected
by the mutex although they are not thread safe
(http://www.fftw.org/doc/Thread-safety.html). So a lock / unlock must
be added around it in itkFFTWCommon.h.
The patch is below, let me know what you think.
Simon

PS: It is also worth of note that I have added a Lock/Unlock in the
BeforeThreadedGenerateData function of my filter to ensure that the
mutex is initialized.

The patch:

@@ -351,7 +350,9 @@ public:
   }
   static void DestroyPlan(PlanType p)
   {
+    FFTWGlobalConfiguration::Lock();
     fftwf_destroy_plan(p);
+    FFTWGlobalConfiguration::Unlock();
   }
 };

@@ -653,7 +654,9 @@ public:
   }
   static void DestroyPlan(PlanType p)
   {
+    FFTWGlobalConfiguration::Lock();
     fftw_destroy_plan(p);
+    FFTWGlobalConfiguration::Unlock();
   }
 };