diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/s390/elision-lock.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/s390/elision-lock.c | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/s390/elision-lock.c b/sysdeps/unix/sysv/linux/s390/elision-lock.c new file mode 100644 index 0000000000..ba5338fbb9 --- /dev/null +++ b/sysdeps/unix/sysv/linux/s390/elision-lock.c @@ -0,0 +1,119 @@ +/* Elided pthread mutex lock. + Copyright (C) 2014 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 <htmintrin.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) +{ + if (*adapt_count > 0) + { + /* Lost updates are possible, but harmless. Due to races this might lead + to *adapt_count becoming less than zero. */ + (*adapt_count)--; + goto use_lock; + } + + __asm__ volatile (".machinemode \"zarch_nohighgprs\"\n\t" + ".machine \"all\"" + : : : "memory"); + + int try_tbegin; + for (try_tbegin = aconf.try_tbegin; + try_tbegin > 0; + try_tbegin--) + { + unsigned status; + if (__builtin_expect + ((status = __builtin_tbegin((void *)0)) == _HTM_TBEGIN_STARTED, 1)) + { + if (*futex == 0) + return 0; + /* Lock was busy. Fall back to normal locking. */ + if (__builtin_expect (__builtin_tx_nesting_depth (), 1)) + { + /* In a non-nested transaction there is no need to abort, + which is expensive. */ + __builtin_tend (); + if (aconf.skip_lock_busy > 0) + *adapt_count = aconf.skip_lock_busy; + goto use_lock; + } + 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. + */ + __builtin_tabort (_HTM_FIRST_USER_ABORT_CODE | 1); + } + } + 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. */ + if (aconf.skip_lock_internal_abort > 0) + *adapt_count = aconf.skip_lock_internal_abort; + goto use_lock; + } + } + } + + /* Same logic as above, but for for a number of temporary failures in a + row. */ + if (aconf.skip_lock_out_of_tbegin_retries > 0 && aconf.try_tbegin > 0) + *adapt_count = aconf.skip_lock_out_of_tbegin_retries; + + use_lock: + return LLL_LOCK ((*futex), private); +} |