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86b4939846
__lll_trylock_elision sets the adapt_count variable too aggressively, and incorrectly on persistent aborts. Taking a cue from s390, adapt_count is only updated if the lock is locked, or a persistent failure occurs. In addition, the abort codes have been renumbered and refactored for clarity. As it stands, glibc only cares if the abort is persistent or not. All aborts are now persistent, excepting a busy lock. This includes changing _ABORT_NESTED_TRYLOCK into a persistent abort. * sysdeps/unix/sysv/linux/powerpc/elision-trylock.c (__lll_trylock_elision): Fix setting of adapt_count. * sysdeps/unix/sysv/linux/powerpc/htm.h (_ABORT_PERSISTENT): Define to clarify persistent aborts. (_ABORT_NESTED_TRYLOCK): Renumber, and make persistent. (_ABORT_SYSCALL): Renumber, and clarify definition. (_ABORT_LOCK_BUSY): Renumber, make non-persistent.
69 lines
2.0 KiB
C
69 lines
2.0 KiB
C
/* elision-trylock.c: Lock eliding trylock for pthreads.
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Copyright (C) 2015 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 <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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#define aconf __elision_aconf
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/* Try to elide a futex trylock. FUTEX is the futex variable. ADAPT_COUNT is
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the adaptation counter in the mutex. */
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int
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__lll_trylock_elision (int *futex, short *adapt_count)
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{
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/* Implement POSIX semantics by forbiding nesting elided trylocks. */
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__builtin_tabort (_ABORT_NESTED_TRYLOCK);
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/* Only try a transaction if it's worth it. */
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if (*adapt_count > 0)
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{
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goto use_lock;
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}
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if (__builtin_tbegin (0))
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{
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if (*futex == 0)
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return 0;
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/* Lock was busy. This is never a nested transaction.
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End it, and set the adapt count. */
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__builtin_tend (0);
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if (aconf.skip_lock_busy > 0)
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*adapt_count = aconf.skip_lock_busy;
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}
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else
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{
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if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
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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 (aconf.skip_trylock_internal_abort > 0)
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*adapt_count = aconf.skip_trylock_internal_abort;
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}
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}
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use_lock:
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return lll_trylock (*futex);
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}
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