Child task management #1
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shintaro-iwasaki
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Apr 6, 2020
llvm/llvm-project@2d4571b TSan spuriously reports for any OpenMP application a race on the initialization of a runtime internal mutex: ``` Atomic read of size 1 at 0x7b6800005940 by thread T4: #0 pthread_mutex_lock <null> (a.out+0x43f39e) #1 __kmp_resume_64 <null> (libomp.so.5+0x84db4) Previous write of size 1 at 0x7b6800005940 by thread T7: #0 pthread_mutex_init <null> (a.out+0x424793) #1 __kmp_suspend_initialize_thread <null> (libomp.so.5+0x8422e) ``` According to @AndreyChurbanov this is a false positive report, as the control flow of the runtime guarantees the ordering of the mutex initialization and the lock: https://software.intel.com/en-us/forums/intel-open-source-openmp-runtime-library/topic/530363 To suppress this report, I suggest the use of TSAN_OPTIONS='ignore_uninstrumented_modules=1'. With this patch, a runtime warning is provided in case an OpenMP application is built with Tsan and executed without this Tsan-option. Reviewed By: jdoerfert Differential Revision: https://reviews.llvm.org/D70412
shintaro-iwasaki
pushed a commit
that referenced
this issue
Apr 26, 2020
TSan spuriously reports for any OpenMP application a race on the initialization of a runtime internal mutex: ``` Atomic read of size 1 at 0x7b6800005940 by thread T4: #0 pthread_mutex_lock <null> (a.out+0x43f39e) #1 __kmp_resume_64 <null> (libomp.so.5+0x84db4) Previous write of size 1 at 0x7b6800005940 by thread T7: #0 pthread_mutex_init <null> (a.out+0x424793) #1 __kmp_suspend_initialize_thread <null> (libomp.so.5+0x8422e) ``` According to @AndreyChurbanov this is a false positive report, as the control flow of the runtime guarantees the ordering of the mutex initialization and the lock: https://software.intel.com/en-us/forums/intel-open-source-openmp-runtime-library/topic/530363 To suppress this report, I suggest the use of TSAN_OPTIONS='ignore_uninstrumented_modules=1'. With this patch, a runtime warning is provided in case an OpenMP application is built with Tsan and executed without this Tsan-option. Reviewed By: jdoerfert Differential Revision: https://reviews.llvm.org/D70412 cherry-pick: 2d4571bf3060f8f3d8417a0ec55e21a280158069 llvm/llvm-project@2d4571b
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The child task management design needs to be improved.
The first implementation is done by checking the queued tasks from the current task to the end of the queue and free those tasks so we can assert that children tasks are completed before the parent one continues.
The future idea is to manage children tasks inside the task structure so each task will be able to check them directly without involving the thread structure
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