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04277e02d7
* All files with FSF copyright notices: Update copyright dates using scripts/update-copyrights. * locale/programs/charmap-kw.h: Regenerated. * locale/programs/locfile-kw.h: Likewise.
89 lines
2.6 KiB
C
89 lines
2.6 KiB
C
/* elision-lock.c: Elided pthread mutex lock.
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Copyright (C) 2015-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <stdio.h>
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#include <pthread.h>
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#include <pthreadP.h>
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#include <lowlevellock.h>
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#include <elision-conf.h>
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#include "htm.h"
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#if !defined(LLL_LOCK) && !defined(EXTRAARG)
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/* Make sure the configuration code is always linked in for static
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libraries. */
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#include "elision-conf.c"
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#endif
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#ifndef EXTRAARG
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# define EXTRAARG
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#endif
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#ifndef LLL_LOCK
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# define LLL_LOCK(a,b) lll_lock(a,b), 0
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#endif
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#define aconf __elision_aconf
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/* Adaptive lock using transactions.
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By default the lock region is run as a transaction, and when it
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aborts or the lock is busy the lock adapts itself. */
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int
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__lll_lock_elision (int *lock, short *adapt_count, EXTRAARG int pshared)
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{
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#ifndef __SPE__
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/* adapt_count is accessed concurrently but is just a hint. Thus,
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use atomic accesses but relaxed MO is sufficient. */
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if (atomic_load_relaxed (adapt_count) > 0)
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{
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goto use_lock;
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}
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for (int i = aconf.try_tbegin; i > 0; i--)
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{
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if (__libc_tbegin (0))
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{
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if (*lock == 0)
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return 0;
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/* Lock was busy. Fall back to normal locking. */
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__libc_tabort (_ABORT_LOCK_BUSY);
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}
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else
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{
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/* A persistent failure indicates that a retry will probably
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result in another failure. Use normal locking now and
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for the next couple of calls. */
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if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
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{
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if (aconf.skip_lock_internal_abort > 0)
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atomic_store_relaxed (adapt_count,
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aconf.skip_lock_internal_abort);
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goto use_lock;
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}
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}
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}
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/* Fall back to locks for a bit if retries have been exhausted */
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if (aconf.try_tbegin > 0 && aconf.skip_lock_out_of_tbegin_retries > 0)
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atomic_store_relaxed (adapt_count,
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aconf.skip_lock_out_of_tbegin_retries);
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use_lock:
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#endif
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return LLL_LOCK ((*lock), pshared);
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}
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