From b1db457bf9ac2c086273c8863b94b3bf814a6dd9 Mon Sep 17 00:00:00 2001 From: Torvald Riegel Date: Thu, 20 Jun 2013 16:40:38 +0000 Subject: [PATCH] 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 --- libitm/ChangeLog | 6 ++++++ libitm/beginend.cc | 10 ++++++++++ 2 files changed, 16 insertions(+) diff --git a/libitm/ChangeLog b/libitm/ChangeLog index ed9114b9147..26001b670bd 100644 --- a/libitm/ChangeLog +++ b/libitm/ChangeLog @@ -1,3 +1,9 @@ +2013-06-20 Torvald Riegel + + PR libitm/57643 + * beginend.cc (gtm_thread::begin_transaction): Handle reentrancy in + the HTM fastpath. + 2013-03-31 Gerald Pfeifer PR bootstrap/56714 diff --git a/libitm/beginend.cc b/libitm/beginend.cc index 93e702efc9e..a3bf5492153 100644 --- a/libitm/beginend.cc +++ b/libitm/beginend.cc @@ -197,6 +197,8 @@ GTM::gtm_thread::begin_transaction (uint32_t prop, const gtm_jmpbuf *jb) // 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 @@ GTM::gtm_thread::begin_transaction (uint32_t prop, const gtm_jmpbuf *jb) 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