diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/x86/elision-lock.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/x86/elision-lock.c | 107 |
1 files changed, 0 insertions, 107 deletions
diff --git a/sysdeps/unix/sysv/linux/x86/elision-lock.c b/sysdeps/unix/sysv/linux/x86/elision-lock.c deleted file mode 100644 index f5ff111dd3..0000000000 --- a/sysdeps/unix/sysv/linux/x86/elision-lock.c +++ /dev/null @@ -1,107 +0,0 @@ -/* elision-lock.c: Elided pthread mutex lock. - Copyright (C) 2011-2017 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 - <http://www.gnu.org/licenses/>. */ - -#include <pthread.h> -#include "pthreadP.h" -#include "lowlevellock.h" -#include "hle.h" -#include <elision-conf.h> - -#if !defined(LLL_LOCK) && !defined(EXTRAARG) -/* Make sure the configuration code is always linked in for static - libraries. */ -#include "elision-conf.c" -#endif - -#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 *futex, short *adapt_count, EXTRAARG int private) -{ - /* adapt_count can be accessed concurrently; these accesses can be both - inside of transactions (if critical sections are nested and the outer - critical section uses lock elision) and outside of transactions. Thus, - we need to use atomic accesses to avoid data races. However, the - value of adapt_count is just a hint, so relaxed MO accesses are - sufficient. */ - if (atomic_load_relaxed (adapt_count) <= 0) - { - unsigned status; - int try_xbegin; - - for (try_xbegin = aconf.retry_try_xbegin; - try_xbegin > 0; - try_xbegin--) - { - if ((status = _xbegin()) == _XBEGIN_STARTED) - { - if (*futex == 0) - return 0; - - /* Lock was busy. Fall back to normal locking. - Could also _xend here but xabort with 0xff code - is more visible in the profiler. */ - _xabort (_ABORT_LOCK_BUSY); - } - - if (!(status & _XABORT_RETRY)) - { - if ((status & _XABORT_EXPLICIT) - && _XABORT_CODE (status) == _ABORT_LOCK_BUSY) - { - /* Right now we skip here. Better would be to wait a bit - and retry. This likely needs some spinning. See - above for why relaxed MO is sufficient. */ - if (atomic_load_relaxed (adapt_count) - != aconf.skip_lock_busy) - atomic_store_relaxed (adapt_count, aconf.skip_lock_busy); - } - /* Internal abort. There is no chance for retry. - Use the normal locking and next time use lock. - Be careful to avoid writing to the lock. See above for why - relaxed MO is sufficient. */ - else if (atomic_load_relaxed (adapt_count) - != aconf.skip_lock_internal_abort) - atomic_store_relaxed (adapt_count, - aconf.skip_lock_internal_abort); - break; - } - } - } - else - { - /* Use a normal lock until the threshold counter runs out. - Lost updates possible. */ - atomic_store_relaxed (adapt_count, - atomic_load_relaxed (adapt_count) - 1); - } - - /* Use a normal lock here. */ - return LLL_LOCK ((*futex), private); -} |