From 8d2c0a593bdefd220be0822fb70de6b8d3bfd39d Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Fri, 7 Nov 2014 12:25:32 -0500 Subject: powerpc: Add the lock elision using HTM This patch adds support for lock elision using ISA 2.07 hardware transactional memory instructions for pthread_mutex primitives. Similar to s390 version, the for elision logic defined in 'force-elision.h' is only enabled if ENABLE_LOCK_ELISION is defined. Also, the lock elision code should be able to be built even with a compiler that does not provide HTM support with builtins. However I have noted the performance is sub-optimal due scheduling pressures. --- sysdeps/unix/sysv/linux/powerpc/elision-trylock.c | 68 +++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 sysdeps/unix/sysv/linux/powerpc/elision-trylock.c (limited to 'sysdeps/unix/sysv/linux/powerpc/elision-trylock.c') diff --git a/sysdeps/unix/sysv/linux/powerpc/elision-trylock.c b/sysdeps/unix/sysv/linux/powerpc/elision-trylock.c new file mode 100644 index 0000000..4a310d5 --- /dev/null +++ b/sysdeps/unix/sysv/linux/powerpc/elision-trylock.c @@ -0,0 +1,68 @@ +/* elision-trylock.c: Lock eliding trylock for pthreads. + 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 + . */ + +#include +#include +#include +#include +#include "htm.h" + +#define aconf __elision_aconf + +/* Try to elide a futex trylock. FUTEX is the futex variable. ADAPT_COUNT is + the adaptation counter in the mutex. */ + +int +__lll_trylock_elision (int *futex, short *adapt_count) +{ + /* Implement POSIX semantics by forbiding nesting elided trylocks. */ + __builtin_tabort (_ABORT_NESTED_TRYLOCK); + + /* Only try a transaction if it's worth it. */ + if (*adapt_count > 0) + { + (*adapt_count)--; + goto use_lock; + } + + if (__builtin_tbegin (0)) + { + if (*futex == 0) + return 0; + + /* Lock was busy. Fall back to normal locking. */ + __builtin_tabort (_ABORT_LOCK_BUSY); + } + else + { + if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ())) + { + /* 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 (aconf.skip_trylock_internal_abort > 0) + *adapt_count = aconf.skip_trylock_internal_abort; + } + + if (aconf.skip_lock_busy > 0) + *adapt_count = aconf.skip_lock_busy; + } + +use_lock: + return lll_trylock (*futex); +} -- cgit v1.1