| /* elision-lock.c: Elided pthread mutex lock. |
| Copyright (C) 2015-2018 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 <stdio.h> |
| #include <pthread.h> |
| #include <pthreadP.h> |
| #include <lowlevellock.h> |
| #include <elision-conf.h> |
| #include "htm.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 *lock, short *adapt_count, EXTRAARG int pshared) |
| { |
| #ifndef __SPE__ |
| /* adapt_count is accessed concurrently but is just a hint. Thus, |
| use atomic accesses but relaxed MO is sufficient. */ |
| if (atomic_load_relaxed (adapt_count) > 0) |
| { |
| goto use_lock; |
| } |
| |
| for (int i = aconf.try_tbegin; i > 0; i--) |
| { |
| if (__libc_tbegin (0)) |
| { |
| if (*lock == 0) |
| return 0; |
| /* Lock was busy. Fall back to normal locking. */ |
| __libc_tabort (_ABORT_LOCK_BUSY); |
| } |
| else |
| { |
| /* A persistent failure indicates that a retry will probably |
| result in another failure. Use normal locking now and |
| for the next couple of calls. */ |
| if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ())) |
| { |
| if (aconf.skip_lock_internal_abort > 0) |
| atomic_store_relaxed (adapt_count, |
| aconf.skip_lock_internal_abort); |
| goto use_lock; |
| } |
| } |
| } |
| |
| /* Fall back to locks for a bit if retries have been exhausted */ |
| if (aconf.try_tbegin > 0 && aconf.skip_lock_out_of_tbegin_retries > 0) |
| atomic_store_relaxed (adapt_count, |
| aconf.skip_lock_out_of_tbegin_retries); |
| |
| use_lock: |
| #endif |
| return LLL_LOCK ((*lock), pshared); |
| } |