| /* elision-lock.c: Elided pthread mutex lock. |
| Copyright (C) 2011-2014 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 "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) |
| { |
| if (*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. */ |
| if (*adapt_count != aconf.skip_lock_busy) |
| *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. */ |
| else if (*adapt_count != aconf.skip_lock_internal_abort) |
| *adapt_count = aconf.skip_lock_internal_abort; |
| break; |
| } |
| } |
| } |
| else |
| { |
| /* Use a normal lock until the threshold counter runs out. |
| Lost updates possible. */ |
| (*adapt_count)--; |
| } |
| |
| /* Use a normal lock here. */ |
| return LLL_LOCK ((*futex), private); |
| } |
