| /* Copyright (C) 2011-2014 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library 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 |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "pthreadP.h" |
| #include <arch/spr_def.h> |
| #include <atomic.h> |
| |
| /* Bound point for bounded exponential backoff */ |
| #define BACKOFF_MAX 2048 |
| |
| /* Initial cycle delay for exponential backoff */ |
| #define BACKOFF_START 32 |
| |
| #ifdef __tilegx__ |
| /* Use cmpexch() after the initial fast-path exch to avoid |
| invalidating the cache line of the lock holder. */ |
| # define TNS(p) atomic_exchange_acq((p), 1) |
| # define CMPTNS(p) atomic_compare_and_exchange_val_acq((p), 1, 0) |
| #else |
| # define TNS(p) __insn_tns(p) |
| # define CMPTNS(p) __insn_tns(p) |
| # define SPR_CYCLE SPR_CYCLE_LOW /* The low 32 bits are sufficient. */ |
| #endif |
| |
| int |
| pthread_spin_lock (pthread_spinlock_t *lock) |
| { |
| if (__builtin_expect (TNS (lock) != 0, 0)) |
| { |
| unsigned int backoff = BACKOFF_START; |
| while (CMPTNS (lock) != 0) |
| { |
| unsigned int start = __insn_mfspr (SPR_CYCLE); |
| while (__insn_mfspr (SPR_CYCLE) - start < backoff) |
| ; |
| if (backoff < BACKOFF_MAX) |
| backoff *= 2; |
| } |
| } |
| return 0; |
| } |
