From mboxrd@z Thu Jan 1 00:00:00 1970 From: paulmck@linux.vnet.ibm.com (Paul E. McKenney) Date: Fri, 18 Jun 2010 11:23:42 -0700 Subject: [ltt-dev] [PATCH RFC] Native ARM7L support In-Reply-To: <20100614021219.GB24614@Krystal> References: <20100612005745.GA28682@linux.vnet.ibm.com> <20100613220129.GM5427@Krystal> <20100614005742.GK2428@linux.vnet.ibm.com> <20100614021219.GB24614@Krystal> Message-ID: <20100618182342.GK2365@linux.vnet.ibm.com> On Sun, Jun 13, 2010 at 10:12:20PM -0400, Mathieu Desnoyers wrote: > * Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote: > > On Sun, Jun 13, 2010 at 06:01:29PM -0400, Mathieu Desnoyers wrote: > > > * Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote: > > > > The machine I am using is cortex-a9. It may be necessary to create a > > > > more intelligent mapping to the many variants of ARM. Interestingly > > > > enough, __sync_synchronize() -still- fails, so use an explicit asm > > > > for the dmb instruction. > > > > > > > > Leaving off the '-O' gives freaking slow results. ;-) > > > > > > Is this -O problem something we should fix at an higher level ? (e.g. for all > > > arch ?) > > > > Might be. In this case, the definition of "freaking slow" is >40ns for > > an empty loop. Though I suspect that getting call_rcu() working would > > be higher priority, and I believe that I have a reasonable approach. > > > > And we are going to need a few RCU-based data structures as well. > > Yep, the next things on the urcu wishlist IMHO would be: > > 1) call_rcu() implementation, derived from defer_rcu() code if appropriate. I have some ideas along this line, and could put together a patch if you would like. > 2) RCU hash tables & RCU binary trees & RCU queues (with lock-free push/pop) > (& stack?) > > There is already some code that exists for most of these, but I'd like to be > comfortable with the implementations (and ideally have some proof that they > actually work) before merging them. I do see the rbtree branch and the various list macros. I do have a few simple RCU-protected stack/queue things. Josh Triplett has done some resizable hash-table work, as has Herbert Xu. But if they aren't up for it, I could see what I can do. Thanx, Paul > Thoughts ? > > Thanks, > > Mathieu > > > > > > More comments below, > > > > > > > > > > > Signed-off-by: Paul E. McKenney > > > > --- > > > > > > > > configure.ac | 4 +++ > > > > urcu/arch_armv7l.h | 59 +++++++++++++++++++++++++++++++++++++++++++++ > > > > urcu/uatomic_arch_armv7l.h | 48 ++++++++++++++++++++++++++++++++++++ > > > > 3 files changed, 111 insertions(+) > > > > > > > > diff --git a/configure.ac b/configure.ac > > > > index 9274337..9e2615f 100644 > > > > --- a/configure.ac > > > > +++ b/configure.ac > > > > @@ -51,6 +51,7 @@ case $host_cpu in > > > > s390x) ARCHTYPE="s390" ;; > > > > sparc64) ARCHTYPE="sparc64" ;; > > > > alpha*) ARCHTYPE="alpha" ;; > > > > + armv7l) ARCHTYPE="armv7l" ;; > > > > *) ARCHTYPE="unknown";; > > > > esac > > > > > > > > @@ -61,6 +62,9 @@ if test "x$ARCHTYPE" != xx86 -a "x$ARCHTYPE" != xppc; then > > > > else > > > > APISRC=tests/api_$ARCHTYPE.h > > > > fi > > > > +if test "x$ARCHTYPE" == xarmv7l; then > > > > + CFLAGS="-mcpu=cortex-a9 -mtune=cortex-a9 -O2" > > > > +fi > > > > > > > > AC_SUBST(ARCHTYPE) > > > > AC_SUBST(SUBARCHTYPE) > > > > diff --git a/urcu/arch_armv7l.h b/urcu/arch_armv7l.h > > > > new file mode 100644 > > > > index 0000000..5920a4d > > > > --- /dev/null > > > > +++ b/urcu/arch_armv7l.h > > > > @@ -0,0 +1,59 @@ > > > > +#ifndef _URCU_ARCH_ARMV7L_H > > > > +#define _URCU_ARCH_ARMV7L_H > > > > + > > > > +/* > > > > + * arch_unknown.h: trivial definitions for the "unknown" 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 128 > > > > + > > > > +#define mb() asm volatile("dmb":::"memory") > > > > + > > > > +#include > > > > +#include > > > > + > > > > +typedef unsigned long long cycles_t; > > > > + > > > > +static inline cycles_t get_cycles (void) > > > > +{ > > > > + cycles_t thetime; > > > > + struct timeval tv; > > > > + > > > > + if (gettimeofday(&tv, NULL) != 0) > > > > + return 0; > > > > + thetime = ((cycles_t)tv.tv_sec) * 1000000ULL + ((cycles_t)tv.tv_usec); > > > > + return (cycles_t)thetime; > > > > +} > > > > + > > > > +#ifdef __cplusplus > > > > +} > > > > +#endif > > > > + > > > > +#include > > > > + > > > > +#endif /* _URCU_ARCH_ARMV7L_H */ > > > > diff --git a/urcu/uatomic_arch_armv7l.h b/urcu/uatomic_arch_armv7l.h > > > > new file mode 100644 > > > > index 0000000..5eece49 > > > > --- /dev/null > > > > +++ b/urcu/uatomic_arch_armv7l.h > > > > @@ -0,0 +1,48 @@ > > > > +#ifndef _URCU_ARCH_UATOMIC_ARMV7L_H > > > > +#define _URCU_ARCH_UATOMIC_ARMV7L_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_unknown.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 > > > > + > > > > +/* xchg */ > > > > +#define uatomic_xchg(addr, v) __sync_lock_test_and_set(addr, v); > > > > > > I expect that these __sync_*() operations have missing memory barriers ? It > > > might be safer to do something like: > > > > > > #define uatomic_cmpxchg(addr, old _new) \ > > > {( \ > > > __typeof__(_new) __ret; \ > > > \ > > > smp_mb(); \ > > > __ret = __sync_val_compare_and_swap(addr, old, _new); \ > > > smp_mb(); \ > > > __ret; > > > )} > > > > > > (similar for other primitives) > > > > > > The idea is that I don't trust gcc's __sync_*() implementation if they got the > > > __sync_synchronize() wrong. > > > > Then there is the question as to whether they used atomics instructions. > > Sigh! > > > > I will run some tests and see what I learn. (Busted disassemblers, but > > I might yet need to hand-decode the instructions...) > > > > Thanx, Paul > > > > > Thanks, > > > > > > Mathieu > > > > > > > + > > > > +/* 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_ARMV7L_H */ > > > > > > -- > > > Mathieu Desnoyers > > > Operating System Efficiency R&D Consultant > > > EfficiOS Inc. > > > http://www.efficios.com > > -- > Mathieu Desnoyers > Operating System Efficiency R&D Consultant > EfficiOS Inc. > http://www.efficios.com