mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-14 15:20:04 +00:00
57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
/* Copyright (C) 2011-2017 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;
|
|
}
|