[ltt-dev] [PATCH RFC] Native ARM7L support

[ltt-dev] [PATCH RFC] Native ARM7L support

[Paul E. McKenney]

Add native support for armv7l.  Other variants of ARM will likely require
separate ports.  Proper handling of "unknown" architectures to follow.

Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
---

 configure.ac               |   13 +++-----
 urcu/arch_armv7l.h         |   59 +++++++++++++++++++++++++++++++++++++
 urcu/uatomic_arch_armv7l.h |   71 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 136 insertions(+), 7 deletions(-)


diff --git a/configure.ac b/configure.ac
index 1b1ca65..8cea997 100644
--- a/configure.ac
+++ b/configure.ac
@@ -51,21 +51,20 @@ case $host_cpu in
 	s390x) ARCHTYPE="s390" ;;
 	sparc64) ARCHTYPE="sparc64" ;;
 	alpha*) ARCHTYPE="alpha" ;;
+	armv7l) ARCHTYPE="armv7l" ;;
 	*) 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$ARCHTYPE" != xppc; then
 	APISRC=tests/api_gcc.h
 else
 	APISRC=tests/api_$ARCHTYPE.h
 fi
+if test "x$ARCHTYPE" == xarmv7l; then
+	CFLAGS="-mcpu=cortex-a9 -mtune=cortex-a9 -O"
+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 <mathieu.desnoyers at polymtl.ca>
+ *
+ * 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 <urcu/compiler.h>
+#include <urcu/config.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif 
+
+/* We don't know, so guess!!! */
+#define CACHE_LINE_SIZE	128
+
+#define mb()    asm volatile("dmb":::"memory")
+
+#include <stdlib.h>
+#include <sys/time.h>
+
+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 <urcu/arch_generic.h>
+
+#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..747a8e5
--- /dev/null
+++ b/urcu/uatomic_arch_armv7l.h
@@ -0,0 +1,71 @@
+#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 <urcu/compiler.h>
+#include <urcu/system.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif 
+
+/* xchg */
+#define uatomic_xchg(addr, v) \
+({ \
+	__typeof__(*addr) __ret; \
+	\
+	smp_mb(); \
+	__ret = __sync_lock_test_and_set(addr, v); \
+	smp_mb(); \
+	__ret; \
+})
+
+/* cmpxchg */
+#define uatomic_cmpxchg(addr, old, _new) \
+({ \
+	__typeof__(*addr) __ret; \
+	\
+	smp_mb(); \
+	__ret = __sync_val_compare_and_swap(addr, old, _new); \
+	smp_mb(); \
+	__ret; \
+})
+
+/* uatomic_add_return */
+#define uatomic_add_return(addr, v) \
+({ \
+	__typeof__(*addr) __ret; \
+	\
+	smp_mb(); \
+	__ret = __sync_add_and_fetch(addr, v); \
+	smp_mb(); \
+	__ret; \
+})
+
+#ifdef __cplusplus 
+}
+#endif
+
+#include <urcu/uatomic_generic.h>
+
+#endif /* _URCU_ARCH_UATOMIC_ARMV7L_H */

[ltt-dev] [PATCH RFC] Native ARM7L support

[Mathieu Desnoyers]

* 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 ?)

More comments below,

> 
> Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
> ---
> 
>  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 <mathieu.desnoyers at polymtl.ca>
> + *
> + * 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 <urcu/compiler.h>
> +#include <urcu/config.h>
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif 
> +
> +/* We don't know, so guess!!! */
> +#define CACHE_LINE_SIZE	128
> +
> +#define mb()    asm volatile("dmb":::"memory")
> +
> +#include <stdlib.h>
> +#include <sys/time.h>
> +
> +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 <urcu/arch_generic.h>
> +
> +#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 <urcu/compiler.h>
> +#include <urcu/system.h>
> +
> +#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.

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 <urcu/uatomic_generic.h>
> +
> +#endif /* _URCU_ARCH_UATOMIC_ARMV7L_H */

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com

[ltt-dev] [PATCH RFC] Native ARM7L support

[Paul E. McKenney]

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.

> More comments below,
> 
> > 
> > Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
> > ---
> > 
> >  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 <mathieu.desnoyers at polymtl.ca>
> > + *
> > + * 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 <urcu/compiler.h>
> > +#include <urcu/config.h>
> > +
> > +#ifdef __cplusplus
> > +extern "C" {
> > +#endif 
> > +
> > +/* We don't know, so guess!!! */
> > +#define CACHE_LINE_SIZE	128
> > +
> > +#define mb()    asm volatile("dmb":::"memory")
> > +
> > +#include <stdlib.h>
> > +#include <sys/time.h>
> > +
> > +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 <urcu/arch_generic.h>
> > +
> > +#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 <urcu/compiler.h>
> > +#include <urcu/system.h>
> > +
> > +#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 <urcu/uatomic_generic.h>
> > +
> > +#endif /* _URCU_ARCH_UATOMIC_ARMV7L_H */
> 
> -- 
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com

[ltt-dev] [PATCH RFC] Native ARM7L support

[Mathieu Desnoyers]

* 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.

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.

Thoughts ?

Thanks,

Mathieu

> 
> > More comments below,
> > 
> > > 
> > > Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
> > > ---
> > > 
> > >  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 <mathieu.desnoyers at polymtl.ca>
> > > + *
> > > + * 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 <urcu/compiler.h>
> > > +#include <urcu/config.h>
> > > +
> > > +#ifdef __cplusplus
> > > +extern "C" {
> > > +#endif 
> > > +
> > > +/* We don't know, so guess!!! */
> > > +#define CACHE_LINE_SIZE	128
> > > +
> > > +#define mb()    asm volatile("dmb":::"memory")
> > > +
> > > +#include <stdlib.h>
> > > +#include <sys/time.h>
> > > +
> > > +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 <urcu/arch_generic.h>
> > > +
> > > +#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 <urcu/compiler.h>
> > > +#include <urcu/system.h>
> > > +
> > > +#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 <urcu/uatomic_generic.h>
> > > +
> > > +#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

[ltt-dev] [PATCH RFC] Native ARM7L support

[Paul E. McKenney]

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 <paulmck at linux.vnet.ibm.com>
> > > > ---
> > > > 
> > > >  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 <mathieu.desnoyers at polymtl.ca>
> > > > + *
> > > > + * 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 <urcu/compiler.h>
> > > > +#include <urcu/config.h>
> > > > +
> > > > +#ifdef __cplusplus
> > > > +extern "C" {
> > > > +#endif 
> > > > +
> > > > +/* We don't know, so guess!!! */
> > > > +#define CACHE_LINE_SIZE	128
> > > > +
> > > > +#define mb()    asm volatile("dmb":::"memory")
> > > > +
> > > > +#include <stdlib.h>
> > > > +#include <sys/time.h>
> > > > +
> > > > +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 <urcu/arch_generic.h>
> > > > +
> > > > +#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 <urcu/compiler.h>
> > > > +#include <urcu/system.h>
> > > > +
> > > > +#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 <urcu/uatomic_generic.h>
> > > > +
> > > > +#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