libitm: Fix handling of reentrancy in the HTM fastpath.
PR libitm/57643
* beginend.cc (gtm_thread::begin_transaction): Handle reentrancy in
the HTM fastpath.
From-SVN: r200250
diff --git a/libitm/beginend.cc b/libitm/beginend.cc
index 93e702e..a3bf549 100644
--- a/libitm/beginend.cc
+++ b/libitm/beginend.cc
@@ -197,6 +197,8 @@
// We are executing a transaction now.
// Monitor the writer flag in the serial-mode lock, and abort
// if there is an active or waiting serial-mode transaction.
+ // Note that this can also happen due to an enclosing
+ // serial-mode transaction; we handle this case below.
if (unlikely(serial_lock.is_write_locked()))
htm_abort();
else
@@ -219,6 +221,14 @@
tx = new gtm_thread();
set_gtm_thr(tx);
}
+ // Check whether there is an enclosing serial-mode transaction;
+ // if so, we just continue as a nested transaction and don't
+ // try to use the HTM fastpath. This case can happen when an
+ // outermost relaxed transaction calls unsafe code that starts
+ // a transaction.
+ if (tx->nesting > 0)
+ break;
+ // Another thread is running a serial-mode transaction. Wait.
serial_lock.read_lock(tx);
serial_lock.read_unlock(tx);
// TODO We should probably reset the retry count t here, unless