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Hi
I am facing a segmentation fault problem when I try to perform asynchronous offload at a later point which I believe is the time when the function returned.
here is the code
functionA real :: WORKN(X,Y,Z) !dir$ offload begin target(MIC:0)signal(1)out(WORKN) do k=1,km . !Lots of code !dir$ end offload end function A functionB real :: Dummy . . ! Do Whatever . . . end function B program run !$OMP PARALLEL DO DEFAULT(SHARED) !this OMP is dummy i.e num_blockblock is 1, can be removed do iblock=1,num_blocks call functionA(iblock) !here is the async offload enddo !$OMP END PARALLEL DO !$OMP PARALLEL DO DEFAULT(SHARED) do iblock=1,num_blocks call functionB(iblock) get segfault when B is running enddo !$OMP END PARALLEL DO end program run
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Where do you wait for the async offload to be completed. I don't see it in the code you posted. I could speculate that the async offload completed after your main program exited since I don't see the wait for the async offload.
Best if you can provide us a small reproduce.
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Without the save attribute, WORKN is a stack variable. You issue an offload which writes into it, and then you return from the function. At some point in time, a write to WORKN occurs, potentially, outside the stack, or into the stack frame of another function.
That is most likely the cause of the problem.
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Also, you cannot use the same signal for multiple threads. Each thread should use a different signal value, you might consider using a reference to a thread stack local variable or a unique variable to the thread, such as the thread ID. *** The OpenMP omp_get_thread_num() will not be a unique number in the event of nested parallelism, so be careful about using that for a unique number.
As mentioned by others, you should also have a signal wait.
Jim Dempsey
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The problem was the missing wait statement. Thank you guys.
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