* peterz@xxxxxxxxxxxxx (peterz@xxxxxxxxxxxxx) wrote:
> We're going to be adding a few new barrier primitives, and in order to
> avoid endless duplication make more agressive use of
> asm-generic/barrier.h.
>
> Change the asm-generic/barrier.h such that it allows partial barrier
> definitions and fills out the rest with defaults.
>
> There are a few architectures (h8300, m32r, m68k) that could probably
> do away with their barrier.h file entirely but are kept for now due to
> their unconventional nop() implementation.
FWIW, we're using a very similar scheme for our memory barrier
implementation in Userspace RCU. We include a generic header at the end,
and we have per-architecture macro override, with ifdefs to see if we
need to use the generic version.
Comments below,
>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
> Cc: Michael Ellerman <michael@xxxxxxxxxxxxxx>
> Cc: Michael Neuling <mikey@xxxxxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Victor Kaplansky <VICTORK@xxxxxxxxxx>
> Suggested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Reviewed-by: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> ---
> arch/alpha/include/asm/barrier.h | 25 ++--------
> arch/arc/include/asm/Kbuild | 1
> arch/arc/include/asm/atomic.h | 5 ++
> arch/arc/include/asm/barrier.h | 42 -----------------
> arch/avr32/include/asm/barrier.h | 17 ++-----
> arch/blackfin/include/asm/barrier.h | 18 -------
> arch/cris/include/asm/Kbuild | 1
> arch/cris/include/asm/barrier.h | 25 ----------
> arch/frv/include/asm/barrier.h | 8 ---
> arch/h8300/include/asm/barrier.h | 21 --------
> arch/hexagon/include/asm/Kbuild | 1
> arch/hexagon/include/asm/barrier.h | 41 -----------------
> arch/m32r/include/asm/barrier.h | 80 ----------------------------------
> arch/m68k/include/asm/barrier.h | 14 -----
> arch/microblaze/include/asm/Kbuild | 1
> arch/microblaze/include/asm/barrier.h | 27 -----------
> arch/mn10300/include/asm/Kbuild | 1
> arch/mn10300/include/asm/barrier.h | 37 ---------------
> arch/parisc/include/asm/Kbuild | 1
> arch/parisc/include/asm/barrier.h | 35 --------------
> arch/score/include/asm/Kbuild | 1
> arch/score/include/asm/barrier.h | 16 ------
> arch/sh/include/asm/barrier.h | 21 +-------
> arch/sparc/include/asm/barrier_32.h | 11 ----
> arch/tile/include/asm/barrier.h | 68 ----------------------------
> arch/unicore32/include/asm/barrier.h | 11 ----
> arch/xtensa/include/asm/barrier.h | 9 ---
> include/asm-generic/barrier.h | 44 ++++++++++++------
> 28 files changed, 64 insertions(+), 518 deletions(-)
>
[...]
> Index: linux-2.6/arch/arc/include/asm/atomic.h
> ===================================================================
> --- linux-2.6.orig/arch/arc/include/asm/atomic.h 2013-11-07 17:03:11.626900787 +0100
> +++ linux-2.6/arch/arc/include/asm/atomic.h 2013-11-07 17:03:11.607900434 +0100
> @@ -190,6 +190,11 @@
>
> #endif /* !CONFIG_ARC_HAS_LLSC */
>
> +#define smp_mb__before_atomic_dec() barrier()
> +#define smp_mb__after_atomic_dec() barrier()
> +#define smp_mb__before_atomic_inc() barrier()
> +#define smp_mb__after_atomic_inc() barrier()
Maybe split the before/after atomic inc/dec change to a separate patch ?
> +
> /**
> * __atomic_add_unless - add unless the number is a given value
> * @v: pointer of type atomic_t
> Index: linux-2.6/arch/arc/include/asm/barrier.h
> ===================================================================
> --- linux-2.6.orig/arch/arc/include/asm/barrier.h 2013-11-07 17:03:11.626900787 +0100
> +++ /dev/null 1970-01-01 00:00:00.000000000 +0000
> @@ -1,42 +0,0 @@
> -/*
> - * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
> - *
> - * This program is free software; you can redistribute it and/or modify
> - * it under the terms of the GNU General Public License version 2 as
> - * published by the Free Software Foundation.
> - */
> -
> -#ifndef __ASM_BARRIER_H
> -#define __ASM_BARRIER_H
> -
> -#ifndef __ASSEMBLY__
> -
> -/* TODO-vineetg: Need to see what this does, don't we need sync anywhere */
> -#define mb() __asm__ __volatile__ ("" : : : "memory")
> -#define rmb() mb()
> -#define wmb() mb()
> -#define set_mb(var, value) do { var = value; mb(); } while (0)
> -#define set_wmb(var, value) do { var = value; wmb(); } while (0)
> -#define read_barrier_depends() mb()
> -
> -/* TODO-vineetg verify the correctness of macros here */
> -#ifdef CONFIG_SMP
> -#define smp_mb() mb()
> -#define smp_rmb() rmb()
> -#define smp_wmb() wmb()
> -#else
> -#define smp_mb() barrier()
> -#define smp_rmb() barrier()
> -#define smp_wmb() barrier()
> -#endif
> -
> -#define smp_mb__before_atomic_dec() barrier()
> -#define smp_mb__after_atomic_dec() barrier()
> -#define smp_mb__before_atomic_inc() barrier()
> -#define smp_mb__after_atomic_inc() barrier()
> -
> -#define smp_read_barrier_depends() do { } while (0)
> -
> -#endif
> -
> -#endif
[...]
> Index: linux-2.6/arch/hexagon/include/asm/barrier.h
> ===================================================================
> --- linux-2.6.orig/arch/hexagon/include/asm/barrier.h 2013-11-07 17:03:11.626900787 +0100
> +++ /dev/null 1970-01-01 00:00:00.000000000 +0000
> @@ -1,41 +0,0 @@
> -/*
> - * Memory barrier definitions for the Hexagon architecture
> - *
> - * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
> - *
> - * This program is free software; you can redistribute it and/or modify
> - * it under the terms of the GNU General Public License version 2 and
> - * only version 2 as published by the Free Software Foundation.
> - *
> - * This program 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 General Public License for more details.
> - *
> - * You should have received a copy of the GNU General Public License
> - * along with this program; if not, write to the Free Software
> - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> - * 02110-1301, USA.
> - */
> -
> -#ifndef _ASM_BARRIER_H
> -#define _ASM_BARRIER_H
> -
> -#define rmb() barrier()
> -#define read_barrier_depends() barrier()
> -#define wmb() barrier()
> -#define mb() barrier()
> -#define smp_rmb() barrier()
> -#define smp_read_barrier_depends() barrier()
> -#define smp_wmb() barrier()
> -#define smp_mb() barrier()
> -#define smp_mb__before_atomic_dec() barrier()
> -#define smp_mb__after_atomic_dec() barrier()
> -#define smp_mb__before_atomic_inc() barrier()
> -#define smp_mb__after_atomic_inc() barrier()
This seems to remove before/after atomic inc/dec for hexagon, but I
don't see where they are added back ?
> -
> -/* Set a value and use a memory barrier. Used by the scheduler somewhere. */
> -#define set_mb(var, value) \
> - do { var = value; mb(); } while (0)
> -
> -#endif /* _ASM_BARRIER_H */
[...]
> Index: linux-2.6/include/asm-generic/barrier.h
> ===================================================================
> --- linux-2.6.orig/include/asm-generic/barrier.h 2013-11-07 17:03:11.626900787 +0100
> +++ linux-2.6/include/asm-generic/barrier.h 2013-11-07 17:03:11.623900731 +0100
> @@ -1,4 +1,5 @@
> -/* Generic barrier definitions, based on MN10300 definitions.
> +/*
> + * Generic barrier definitions, originally based on MN10300 definitions.
> *
> * It should be possible to use these on really simple architectures,
> * but it serves more as a starting point for new ports.
> @@ -16,35 +17,50 @@
>
> #ifndef __ASSEMBLY__
>
> -#define nop() asm volatile ("nop")
> +#include <linux/compiler.h>
> +
> +#ifndef nop
> +#define nop() asm volatile ("nop")
> +#endif
>
I don't really understand why "no-op" sits within barrier.h. It might be
a lack of imagination on my part though.
Other than that
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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