From mboxrd@z Thu Jan 1 00:00:00 1970 From: mathieu.desnoyers@efficios.com (Mathieu Desnoyers) Date: Sun, 13 Jun 2010 17:28:28 -0400 Subject: [ltt-dev] [PATCH 1/3] Fix the "unknown" case In-Reply-To: <1276286430-21147-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20100611195937.GA18891@linux.vnet.ibm.com> <1276286430-21147-1-git-send-email-paulmck@linux.vnet.ibm.com> Message-ID: <20100613212828.GG5427@Krystal> * Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote: > Use a back-to-back pair of pthread_mutex_lock acquisitions and releases > to stand in for a memory barrier, given that ARM doesn't seem to do > the right thing with __sync_synchronize(). Tested on ARM and on x86. > The x86 testing was performed by removing all of the x86-specific > tests from configure.ac and then building from scratch. > > Signed-off-by: Paul E. McKenney > --- > configure.ac | 9 +--- > urcu/arch_unknown.h | 87 +++++++++++++++++++++++++++++++++++++++++++ > urcu/uatomic_arch_unknown.h | 57 ++++++++++++++++++++++++++++ > 3 files changed, 146 insertions(+), 7 deletions(-) > create mode 100644 urcu/arch_unknown.h > create mode 100644 urcu/uatomic_arch_unknown.h > > diff --git a/configure.ac b/configure.ac > index 1b1ca65..9274337 100644 > --- a/configure.ac > +++ b/configure.ac > @@ -54,13 +54,8 @@ case $host_cpu in > *) ARCHTYPE="unknown";; > esac > > -if test "$ARCHTYPE" != "unknown"; then > - UATOMICSRC=urcu/uatomic_arch_$ARCHTYPE.h > - ARCHSRC=urcu/arch_$ARCHTYPE.h > -else > - UATOMICSRC=urcu/uatomic_generic.h > - ARCHSRC=urcu/arch_generic.h > -fi > +UATOMICSRC=urcu/uatomic_arch_$ARCHTYPE.h > +ARCHSRC=urcu/arch_$ARCHTYPE.h > if test "x$ARCHTYPE" != xx86 -a "x$ARCHTYPE" != xppc; then > APISRC=tests/api_gcc.h > else > diff --git a/urcu/arch_unknown.h b/urcu/arch_unknown.h > new file mode 100644 > index 0000000..3f78310 > --- /dev/null > +++ b/urcu/arch_unknown.h > @@ -0,0 +1,87 @@ > +#ifndef _URCU_ARCH_ARMV7_H > +#define _URCU_ARCH_ARMV7_H > + > +/* > + * arch_armv7.h: trivial definitions for the ARMv7-A/R architecture. > + * > + * Copyright (c) 2010 Paul E. McKenney, IBM Corporation. > + * Copyright (c) 2009 Mathieu Desnoyers > + * > + * This 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. > +* > + * This 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 this library; if not, write to the Free Software > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA > + */ > + > +#include > +#include > + > +#ifdef __cplusplus > +extern "C" { > +#endif > + > +/* We don't know, so guess!!! */ > +#define CACHE_LINE_SIZE 64 > + > +#define mb() \ > + do { \ > + pthread_mutex_t __mb_fake_mutex; \ Can you give a hint telling why this double mutex acquire-release produces the equivalent of a memory barrier ? Some comments would be welcome in the code. Commenting that this mutex is declared on the local function stack would be appropriate too (I had my mind in a twist at first thinking it was somehow static). BTW, I don't think it is required to keep the next patch separate. Folding it into this patch will probably make the following discussion easier. Thanks! Mathieu > + \ > + pthread_mutex_init(&__mb_fake_mutex, NULL); \ > + if (pthread_mutex_lock(&__mb_fake_mutex) != 0) { \ > + perror("pthread_mutex_lock"); \ > + abort(); \ > + } \ > + if (pthread_mutex_unlock(&__mb_fake_mutex) != 0) { \ > + perror("pthread_mutex_lock"); \ > + abort(); \ > + } \ > + if (pthread_mutex_lock(&__mb_fake_mutex) != 0) { \ > + perror("pthread_mutex_lock"); \ > + abort(); \ > + } \ > + if (pthread_mutex_unlock(&__mb_fake_mutex) != 0) { \ > + perror("pthread_mutex_lock"); \ > + abort(); \ > + } \ > + } while (0) > + > +/* > + * Serialize core instruction execution. Also acts as a compiler barrier. > + */ > +#define sync_core() asm volatile("isb" : : : "memory") > + > +#include > +#include > + > +typedef unsigned long long cycles_t; > + > +static inline cycles_t get_cycles (void) > +{ > + long long thetime; > + struct timeval tv; > + > + if (gettimeofday(&tv, NULL) != 0) { > + perror("gettimeofday"); > + abort(); > + } > + thetime = ((long long)tv.tv_sec) * 1000000ULL + ((long long)tv.tv_usec); > + return (cycles_t)thetime; > +} > + > +#ifdef __cplusplus > +} > +#endif > + > +#include > + > +#endif /* _URCU_ARCH_ARMV7_H */ > diff --git a/urcu/uatomic_arch_unknown.h b/urcu/uatomic_arch_unknown.h > new file mode 100644 > index 0000000..d1cf93e > --- /dev/null > +++ b/urcu/uatomic_arch_unknown.h > @@ -0,0 +1,57 @@ > +#ifndef _URCU_ARCH_UATOMIC_ARMV7_H > +#define _URCU_ARCH_UATOMIC_ARMV7_H > + > +/* > + * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved. > + * Copyright (c) 1996-1999 by Silicon Graphics. All rights reserved. > + * Copyright (c) 1999-2004 Hewlett-Packard Development Company, L.P. > + * Copyright (c) 2009 Mathieu Desnoyers > + * Copyright (c) 2010 Paul E. McKenney, IBM Corporation > + * (Adapted from uatomic_arch_ppc.h) > + * > + * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED > + * OR IMPLIED. ANY USE IS AT YOUR OWN RISK. > + * > + * Permission is hereby granted to use or copy this program > + * for any purpose, provided the above notices are retained on all copies. > + * Permission to modify the code and to distribute modified code is granted, > + * provided the above notices are retained, and a notice that the code was > + * modified is included with the above copyright notice. > + * > + * Code inspired from libuatomic_ops-1.2, inherited in part from the > + * Boehm-Demers-Weiser conservative garbage collector. > + */ > + > +#include > +#include > + > +#ifdef __cplusplus > +extern "C" { > +#endif > + > +#define ILLEGAL_INSTR ".long 0xd00d00" /* @@@FIXME from ppc to ARM. */ > + > +/* > + * Using a isync as second barrier for exchange to provide acquire semantic. > + * According to uatomic_ops/sysdeps/gcc/powerpc.h, the documentation is "fairly > + * explicit that this also has acquire semantics." > + * Derived from AO_compare_and_swap(), but removed the comparison. > + */ > + > +/* xchg */ > +#define uatomic_xchg(addr, v) __sync_lock_test_and_set(addr, v); > + > +/* cmpxchg */ > +#define uatomic_cmpxchg(addr, old, _new) \ > + __sync_val_compare_and_swap(addr, old, _new) > + > +/* uatomic_add_return */ > +#define uatomic_add_return(addr, v) __sync_add_and_fetch(addr, v) > + > +#ifdef __cplusplus > +} > +#endif > + > +#include > + > +#endif /* _URCU_ARCH_UATOMIC_ARMV7_H */ > -- > 1.7.0.6 > -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com