[Openmp-commits] [PATCH] D77603: [OpenMP] Sync writes to child thread's data before reduction

[Bryan Chan via Phabricator via Openmp-commits]

bryanpkc updated this revision to Diff 256954.
bryanpkc added a comment.

Add a paired memory barrier to the child thread's path after it finishes writing to its own data and before releasing the parent thread.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77603/new/

https://reviews.llvm.org/D77603

Files:
  openmp/runtime/src/kmp_barrier.cpp


Index: openmp/runtime/src/kmp_barrier.cpp
===================================================================
--- openmp/runtime/src/kmp_barrier.cpp
+++ openmp/runtime/src/kmp_barrier.cpp
@@ -538,6 +538,8 @@
         __itt_get_timestamp();
   }
 #endif
+  KMP_MB(); // Synchronize writes to child threads.
+
   /* Perform a hypercube-embedded tree gather to wait until all of the threads
      have arrived, and reduce any required data as we go.  */
   kmp_flag_64 p_flag(&thr_bar->b_arrived);
@@ -589,6 +591,7 @@
       // Wait for child to arrive
       kmp_flag_64 c_flag(&child_bar->b_arrived, new_state);
       c_flag.wait(this_thr, FALSE USE_ITT_BUILD_ARG(itt_sync_obj));
+      KMP_MB(); // Synchronize writes to child threads.
       ANNOTATE_BARRIER_END(child_thr);
 #if USE_ITT_BUILD && USE_ITT_NOTIFY
       // Barrier imbalance - write min of the thread time and a child time to


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D77603.256954.patch
Type: text/x-patch
Size: 893 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/openmp-commits/attachments/20200413/69312461/attachment.bin>