mirror of
https://sourceware.org/git/glibc.git
synced 2025-10-30 10:45:40 +03:00
82 lines
2.4 KiB
C
82 lines
2.4 KiB
C
/* elision-lock.c: Elided pthread mutex lock.
|
|
Copyright (C) 2015-2024 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <stdio.h>
|
|
#include <pthread.h>
|
|
#include <pthreadP.h>
|
|
#include <lowlevellock.h>
|
|
#include <elision-conf.h>
|
|
#include "htm.h"
|
|
|
|
#ifndef EXTRAARG
|
|
# define EXTRAARG
|
|
#endif
|
|
#ifndef LLL_LOCK
|
|
# define LLL_LOCK(a,b) lll_lock(a,b), 0
|
|
#endif
|
|
|
|
#define aconf __elision_aconf
|
|
|
|
/* Adaptive lock using transactions.
|
|
By default the lock region is run as a transaction, and when it
|
|
aborts or the lock is busy the lock adapts itself. */
|
|
|
|
int
|
|
__lll_lock_elision (int *lock, short *adapt_count, EXTRAARG int pshared)
|
|
{
|
|
/* adapt_count is accessed concurrently but is just a hint. Thus,
|
|
use atomic accesses but relaxed MO is sufficient. */
|
|
if (atomic_load_relaxed (adapt_count) > 0)
|
|
{
|
|
goto use_lock;
|
|
}
|
|
|
|
for (int i = aconf.try_tbegin; i > 0; i--)
|
|
{
|
|
if (__libc_tbegin (0))
|
|
{
|
|
if (*lock == 0)
|
|
return 0;
|
|
/* Lock was busy. Fall back to normal locking. */
|
|
__libc_tabort (_ABORT_LOCK_BUSY);
|
|
}
|
|
else
|
|
{
|
|
/* A persistent failure indicates that a retry will probably
|
|
result in another failure. Use normal locking now and
|
|
for the next couple of calls. */
|
|
if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
|
|
{
|
|
if (aconf.skip_lock_internal_abort > 0)
|
|
atomic_store_relaxed (adapt_count,
|
|
aconf.skip_lock_internal_abort);
|
|
goto use_lock;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Fall back to locks for a bit if retries have been exhausted */
|
|
if (aconf.try_tbegin > 0 && aconf.skip_lock_out_of_tbegin_retries > 0)
|
|
atomic_store_relaxed (adapt_count,
|
|
aconf.skip_lock_out_of_tbegin_retries);
|
|
|
|
use_lock:
|
|
return LLL_LOCK ((*lock), pshared);
|
|
}
|
|
libc_hidden_def (__lll_lock_elision)
|