libitm: Ensure proxy privatization safety.

	* method-gl.cc (gl_wt_dispatch::trycommit): Ensure proxy privatization
	safety.
	* method-ml.cc (ml_wt_dispatch::trycommit): Likewise.
	* libitm/testsuite/libitm.c/priv-1.c: New.

From-SVN: r232469

1 files changed, 15 insertions, 0 deletions

diff --git a/libitm/method-ml.cc b/libitm/method-ml.cc
index 723643a..c1a6771 100644
--- a/libitm/method-ml.cc
+++ b/libitm/method-ml.cc
@@ -513,6 +513,21 @@ public:
     if (!tx->writelog.size())
       {
         tx->readlog.clear();
+        // We still need to ensure privatization safety, unfortunately.  While
+        // we cannot have privatized anything by ourselves (because we are not
+        // an update transaction), we can have observed the commits of
+        // another update transaction that privatized something.  Because any
+        // commit happens before ensuring privatization, our snapshot and
+        // commit can thus have happened before ensuring privatization safety
+        // for this commit/snapshot time.  Therefore, before we can return to
+        // nontransactional code that might use the privatized data, we must
+        // ensure privatization safety for our snapshot time.
+        // This still seems to be better than not allowing use of the
+        // snapshot time before privatization safety has been ensured because
+        // we at least can run transactions such as this one, and in the
+        // meantime the transaction producing this commit time might have
+        // finished ensuring privatization safety for it.
+        priv_time = tx->shared_state.load(memory_order_relaxed);
         return true;
       }