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Diffstat (limited to 'libitm/config/linux/rwlock.h')
-rw-r--r-- | libitm/config/linux/rwlock.h | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/libitm/config/linux/rwlock.h b/libitm/config/linux/rwlock.h new file mode 100644 index 00000000000..7e6229b73f2 --- /dev/null +++ b/libitm/config/linux/rwlock.h @@ -0,0 +1,66 @@ +/* Copyright (C) 2011 Free Software Foundation, Inc. + Contributed by Torvald Riegel <triegel@redhat.com>. + + This file is part of the GNU Transactional Memory Library (libitm). + + Libitm is free software; you can redistribute it and/or modify it + under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + Libitm is distributed in the hope that it will be useful, but WITHOUT ANY + WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS + FOR A PARTICULAR PURPOSE. See the GNU General Public License for + more details. + + Under Section 7 of GPL version 3, you are granted additional + permissions described in the GCC Runtime Library Exception, version + 3.1, as published by the Free Software Foundation. + + You should have received a copy of the GNU General Public License and + a copy of the GCC Runtime Library Exception along with this program; + see the files COPYING3 and COPYING.RUNTIME respectively. If not, see + <http://www.gnu.org/licenses/>. */ + +#ifndef GTM_RWLOCK_H +#define GTM_RWLOCK_H + +#include "common.h" + +namespace GTM HIDDEN { + +struct gtm_thread; + +// This datastructure is the blocking, futex-based version of the Dekker-style +// reader-writer lock used to provide mutual exclusion between active and +// serial transactions. +// See libitm's documentation for further details. +// +// In this implementation, writers are given highest priority access but +// read-to-write upgrades do not have a higher priority than writers. + +class gtm_rwlock +{ + // TODO Put futexes on different cachelines? + int writers; // Writers' futex. + int writer_readers; // A confirmed writer waits here for readers. + int readers; // Readers wait here for writers (iff true). + + public: + gtm_rwlock() : writers(0), writer_readers(0), readers(0) {}; + + void read_lock (gtm_thread *tx); + void read_unlock (gtm_thread *tx); + + void write_lock (); + void write_unlock (); + + bool write_upgrade (gtm_thread *tx); + + protected: + bool write_lock_generic (gtm_thread *tx); +}; + +} // namespace GTM + +#endif // GTM_RWLOCK_H |