diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/s390/elision-lock.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/s390/elision-lock.c | 125 |
1 files changed, 0 insertions, 125 deletions
diff --git a/sysdeps/unix/sysv/linux/s390/elision-lock.c b/sysdeps/unix/sysv/linux/s390/elision-lock.c deleted file mode 100644 index 00815375c7..0000000000 --- a/sysdeps/unix/sysv/linux/s390/elision-lock.c +++ /dev/null @@ -1,125 +0,0 @@ -/* Elided pthread mutex lock. - Copyright (C) 2014-2017 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 <htm.h> -#include <elision-conf.h> -#include <stdint.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 && aconf.try_tbegin > 0) - { - /* Start a transaction and retry it automatically if it aborts with - _HTM_TBEGIN_TRANSIENT. This macro calls tbegin at most retry_cnt - + 1 times. The second argument is considered as retry_cnt. */ - int status = __libc_tbegin_retry ((void *) 0, aconf.try_tbegin - 1); - if (__glibc_likely (status == _HTM_TBEGIN_STARTED)) - { - /* Check the futex to make sure nobody has touched it in the - mean time. This forces the futex into the cache and makes - sure the transaction aborts if another thread acquires the lock - concurrently. */ - if (__glibc_likely (atomic_load_relaxed (futex) == 0)) - /* Lock was free. Return to user code in a transaction. */ - return 0; - - /* Lock was busy. Fall back to normal locking. - This can be the case if e.g. adapt_count was decremented to zero - by a former release and another thread has been waken up and - acquired it. */ - if (__glibc_likely (__libc_tx_nesting_depth () <= 1)) - { - /* In a non-nested transaction there is no need to abort, - which is expensive. Simply end the started transaction. */ - __libc_tend (); - /* Don't try to use transactions for the next couple of times. - See above for why relaxed MO is sufficient. */ - if (aconf.skip_lock_busy > 0) - atomic_store_relaxed (adapt_count, aconf.skip_lock_busy); - } - else /* nesting depth is > 1 */ - { - /* A nested transaction will abort eventually because it - cannot make any progress before *futex changes back to 0. - So we may as well abort immediately. - This persistently aborts the outer transaction to force - the outer mutex use the default lock instead of retrying - with transactions until the try_tbegin of the outer mutex - is zero. - The adapt_count of this inner mutex is not changed, - because using the default lock with the inner mutex - would abort the outer transaction. */ - __libc_tabort (_HTM_FIRST_USER_ABORT_CODE | 1); - __builtin_unreachable (); - } - } - else if (status != _HTM_TBEGIN_TRANSIENT) - { - /* A persistent abort (cc 1 or 3) indicates that a retry is - probably futile. Use the normal locking now and for the - next couple of calls. - Be careful to avoid writing to the lock. See above for why - relaxed MO is sufficient. */ - if (aconf.skip_lock_internal_abort > 0) - atomic_store_relaxed (adapt_count, - aconf.skip_lock_internal_abort); - } - else - { - /* The transaction failed for some retries with - _HTM_TBEGIN_TRANSIENT. Use the normal locking now and for the - next couple of calls. */ - if (aconf.skip_lock_out_of_tbegin_retries > 0) - atomic_store_relaxed (adapt_count, - aconf.skip_lock_out_of_tbegin_retries); - } - } - - /* Use normal locking as fallback path if the transaction does not - succeed. */ - return LLL_LOCK ((*futex), private); -} |