| /* Copyright (C) 2009-2014 Free Software Foundation, Inc. |
| Contributed by Richard Henderson <rth@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 LIBITM_STMLOCK_H |
| #define LIBITM_STMLOCK_H 1 |
| |
| namespace GTM HIDDEN { |
| |
| /* A versioned write lock on a cacheline. This must be wide enough to |
| store a pointer, and preferably wide enough to avoid overflowing the |
| version counter. Thus we use a "word", which should be 64-bits on |
| 64-bit systems even when their pointer size is forced smaller. */ |
| typedef gtm_word gtm_stmlock; |
| |
| /* This has to be the same size as gtm_stmlock, we just use this name |
| for documentation purposes. */ |
| typedef gtm_word gtm_version; |
| |
| /* The maximum value a version number can have. This is a consequence |
| of having the low bit of gtm_stmlock reserved for the owned bit. */ |
| #define GTM_VERSION_MAX (~(gtm_version)0 >> 1) |
| |
| /* A value that may be used to indicate "uninitialized" for a version. */ |
| #define GTM_VERSION_INVALID (~(gtm_version)0) |
| |
| /* This bit is set when the write lock is held. When set, the balance of |
| the bits in the lock is a pointer that references STM backend specific |
| data; it is up to the STM backend to determine if this thread holds the |
| lock. If this bit is clear, the balance of the bits are the last |
| version number committed to the cacheline. */ |
| static inline bool |
| gtm_stmlock_owned_p (gtm_stmlock lock) |
| { |
| return lock & 1; |
| } |
| |
| static inline gtm_stmlock |
| gtm_stmlock_set_owned (void *data) |
| { |
| return (gtm_stmlock)(uintptr_t)data | 1; |
| } |
| |
| static inline void * |
| gtm_stmlock_get_addr (gtm_stmlock lock) |
| { |
| return (void *)((uintptr_t)lock & ~(uintptr_t)1); |
| } |
| |
| static inline gtm_version |
| gtm_stmlock_get_version (gtm_stmlock lock) |
| { |
| return lock >> 1; |
| } |
| |
| static inline gtm_stmlock |
| gtm_stmlock_set_version (gtm_version ver) |
| { |
| return ver << 1; |
| } |
| |
| /* We use a fixed set of locks for all memory, hashed into the |
| following table. */ |
| #define LOCK_ARRAY_SIZE (1024 * 1024) |
| extern gtm_stmlock gtm_stmlock_array[LOCK_ARRAY_SIZE]; |
| |
| static inline gtm_stmlock * |
| gtm_get_stmlock (const gtm_cacheline *addr) |
| { |
| size_t idx = ((uintptr_t) addr / CACHELINE_SIZE) % LOCK_ARRAY_SIZE; |
| return gtm_stmlock_array + idx; |
| } |
| |
| /* The current global version number. */ |
| extern atomic<gtm_version> gtm_clock; |
| |
| static inline gtm_version |
| gtm_get_clock (void) |
| { |
| atomic_thread_fence(memory_order_release); |
| return gtm_clock.load(memory_order_acquire); |
| } |
| |
| static inline gtm_version |
| gtm_inc_clock (void) |
| { |
| /* ??? Here we have a choice, the pre-inc operator mapping to |
| __atomic_add_fetch with memory_order_seq_cst, or fetch_add |
| with memory_order_acq_rel plus another separate increment. |
| We really ought to recognize and optimize fetch_op(x) op x... */ |
| gtm_version r = ++gtm_clock; |
| |
| /* ??? Ought to handle wraparound for 32-bit. */ |
| if (sizeof(r) < 8 && r > GTM_VERSION_MAX) |
| abort (); |
| |
| return r; |
| } |
| |
| } // namespace GTM |
| |
| #endif // LIBITM_STMLOCK_H |