[ltt-dev] [PATCH 06/12] add uatomic_defaults.h, use it for default definitions
Mathieu Desnoyers
compudj at krystal.dyndns.org
Wed Feb 17 22:10:21 EST 2010
* Paolo Bonzini (pbonzini at redhat.com) wrote:
> uatomic_defaults.h can be included by uatomic_arch_*.h to provide useful
Maybe rebrand defaults -> generic here too ?
More comments inline.
> default definitions. uatomic_arch_*.h can define whatever builtins
> it wants to override, then uatomic_defaults.h will provide what is not
> already defined, as follows:
>
> - uatomic_cmpxchg will use __sync_val_compare_and_swap builtins;
>
> - uatomic_add_return will use __sync_fetch_and_add if uatomic_arch_*.h
> did not provide a definition of uatomic_cmpxchg. If it did, we assume
> __sync builtins are buggy or otherwise undesirable on this platform,
> so uatomic_defaults.h will implement uatomic_add_return in terms of
> uatomic_cmpxchg too.
>
> - uatomic_xchg is like uatomic_add_return. However, since GCC does
> not provide an adequate builtin, it needs to use a compare-and-swap
> loop using __sync_bool_compare_and_swap if uatomic_cmpxchg is not
> provided.
>
> - uatomic_sub_return/uatomic_add/uatomic_sub will be implemented
> in terms of uatomic_add_return;
>
> - uatomic_inc/uatomic_dec will be implemented in terms of uatomic_add.
>
> After this patch, uatomic_defaults.h is already used for the latter two
> categories.
>
> The hunk in tests/test_uatomic.c is only needed for bisectability
> and will be removed later.
>
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> ---
> Makefile.am | 2 +-
> tests/test_uatomic.c | 2 +
> urcu/uatomic_arch_ppc.h | 15 +--
> urcu/uatomic_arch_s390.h | 15 +--
> urcu/uatomic_arch_sparc64.h | 15 +--
> urcu/uatomic_arch_x86.h | 26 ++---
> urcu/uatomic_defaults.h | 262 +++++++++++++++++++++++++++++++++++++++++++
> 7 files changed, 280 insertions(+), 57 deletions(-)
> create mode 100644 urcu/uatomic_defaults.h
>
> diff --git a/Makefile.am b/Makefile.am
> index 2ede9e0..c91dfe9 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -6,7 +6,7 @@ SUBDIRS = . tests
>
> include_HEADERS = urcu.h $(top_srcdir)/urcu-*.h
> nobase_dist_include_HEADERS = urcu/compiler.h urcu/hlist.h urcu/list.h \
> - urcu/rculist.h urcu/system.h urcu/urcu-futex.h
> + urcu/rculist.h urcu/system.h urcu/urcu-futex.h urcu/uatomic_defaults.h
> nobase_nodist_include_HEADERS = urcu/arch.h urcu/uatomic_arch.h urcu/config.h
>
> EXTRA_DIST = $(top_srcdir)/urcu/arch_*.h $(top_srcdir)/urcu/uatomic_arch_*.h \
> diff --git a/tests/test_uatomic.c b/tests/test_uatomic.c
> index 68cb6df..c0f36fe 100644
> --- a/tests/test_uatomic.c
> +++ b/tests/test_uatomic.c
> @@ -1,5 +1,7 @@
> #include <stdio.h>
> #include <assert.h>
> +
> +#define UATOMIC_NO_LINK_ERROR
> #include <urcu/uatomic_arch.h>
>
> #if (defined(__i386__) || defined(__x86_64__))
> diff --git a/urcu/uatomic_arch_ppc.h b/urcu/uatomic_arch_ppc.h
> index 8da192e..b42bfdb 100644
> --- a/urcu/uatomic_arch_ppc.h
> +++ b/urcu/uatomic_arch_ppc.h
> @@ -47,9 +47,6 @@ extern "C" {
>
> #define ILLEGAL_INSTR ".long 0xd00d00"
>
> -#define uatomic_set(addr, v) STORE_SHARED(*(addr), (v))
> -#define uatomic_read(addr) LOAD_SHARED(*(addr))
> -
> /*
> * Using a isync as second barrier for exchange to provide acquire semantic.
> * According to uatomic_ops/sysdeps/gcc/powerpc.h, the documentation is "fairly
> @@ -225,18 +222,10 @@ unsigned long _uatomic_add_return(void *addr, unsigned long val,
> (unsigned long)(v), \
> sizeof(*(addr))))
>
> -/* uatomic_sub_return, uatomic_add, uatomic_sub, uatomic_inc, uatomic_dec */
> -
> -#define uatomic_sub_return(addr, v) uatomic_add_return((addr), -(v))
> -
> -#define uatomic_add(addr, v) (void)uatomic_add_return((addr), (v))
> -#define uatomic_sub(addr, v) (void)uatomic_sub_return((addr), (v))
> -
> -#define uatomic_inc(addr) uatomic_add((addr), 1)
> -#define uatomic_dec(addr) uatomic_add((addr), -1)
> -
> #ifdef __cplusplus
> }
> #endif
>
> +#include <urcu/uatomic_defaults.h>
> +
> #endif /* _URCU_ARCH_UATOMIC_PPC_H */
> diff --git a/urcu/uatomic_arch_s390.h b/urcu/uatomic_arch_s390.h
> index 614867f..8f1523c 100644
> --- a/urcu/uatomic_arch_s390.h
> +++ b/urcu/uatomic_arch_s390.h
> @@ -78,9 +78,6 @@ struct __uatomic_dummy {
> };
> #define __hp(x) ((struct __uatomic_dummy *)(x))
>
> -#define uatomic_set(addr, v) STORE_SHARED(*(addr), (v))
> -#define uatomic_read(addr) LOAD_SHARED(*(addr))
> -
> /* xchg */
>
> static inline __attribute__((always_inline))
> @@ -208,18 +205,10 @@ unsigned long _uatomic_add_return(void *addr, unsigned long val, int len)
> (unsigned long)(v), \
> sizeof(*(addr))))
>
> -/* uatomic_sub_return, uatomic_add, uatomic_sub, uatomic_inc, uatomic_dec */
> -
> -#define uatomic_sub_return(addr, v) uatomic_add_return((addr), -(v))
> -
> -#define uatomic_add(addr, v) (void)uatomic_add_return((addr), (v))
> -#define uatomic_sub(addr, v) (void)uatomic_sub_return((addr), (v))
> -
> -#define uatomic_inc(addr) uatomic_add((addr), 1)
> -#define uatomic_dec(addr) uatomic_add((addr), -1)
> -
> #ifdef __cplusplus
> }
> #endif
>
> +#include <urcu/uatomic_defaults.h>
> +
> #endif /* _URCU_UATOMIC_ARCH_S390_H */
> diff --git a/urcu/uatomic_arch_sparc64.h b/urcu/uatomic_arch_sparc64.h
> index d443d4f..0c16eaf 100644
> --- a/urcu/uatomic_arch_sparc64.h
> +++ b/urcu/uatomic_arch_sparc64.h
> @@ -39,9 +39,6 @@ extern "C" {
> #define BITS_PER_LONG (__SIZEOF_LONG__ * 8)
> #endif
>
> -#define uatomic_set(addr, v) STORE_SHARED(*(addr), (v))
> -#define uatomic_read(addr) LOAD_SHARED(*(addr))
> -
> /* cmpxchg */
>
> static inline __attribute__((always_inline))
> @@ -169,18 +166,10 @@ unsigned long _uatomic_add_return(void *addr, unsigned long val, int len)
> (unsigned long)(v), \
> sizeof(*(addr))))
>
> -/* uatomic_sub_return, uatomic_add, uatomic_sub, uatomic_inc, uatomic_dec */
> -
> -#define uatomic_sub_return(addr, v) uatomic_add_return((addr), -(v))
> -
> -#define uatomic_add(addr, v) (void)uatomic_add_return((addr), (v))
> -#define uatomic_sub(addr, v) (void)uatomic_sub_return((addr), (v))
> -
> -#define uatomic_inc(addr) uatomic_add((addr), 1)
> -#define uatomic_dec(addr) uatomic_add((addr), -1)
> -
> #ifdef __cplusplus
> }
> #endif
>
> +#include <urcu/uatomic_defaults.h>
> +
> #endif /* _URCU_ARCH_UATOMIC_PPC_H */
> diff --git a/urcu/uatomic_arch_x86.h b/urcu/uatomic_arch_x86.h
> index 3bfe86d..8a81995 100644
> --- a/urcu/uatomic_arch_x86.h
> +++ b/urcu/uatomic_arch_x86.h
> @@ -49,7 +49,11 @@ struct __uatomic_dummy {
> #define __hp(x) ((struct __uatomic_dummy *)(x))
>
> #define _uatomic_set(addr, v) STORE_SHARED(*(addr), (v))
> +
> +#if 0
> +/* Read is atomic even in compat mode */
> #define _uatomic_read(addr) LOAD_SHARED(*(addr))
> +#endif
Maybe we should fix this by removing it entirely, just leaving the
comment below in the "compat_" block ?
>
> /* cmpxchg */
>
> @@ -176,7 +180,7 @@ unsigned long __uatomic_exchange(void *addr, unsigned long val, int len)
> ((__typeof__(*(addr))) __uatomic_exchange((addr), (unsigned long)(v), \
> sizeof(*(addr))))
>
> -/* uatomic_add_return, uatomic_sub_return */
> +/* uatomic_add_return */
>
> static inline __attribute__((always_inline))
> unsigned long __uatomic_add_return(void *addr, unsigned long val,
> @@ -241,9 +245,7 @@ unsigned long __uatomic_add_return(void *addr, unsigned long val,
> (unsigned long)(v), \
> sizeof(*(addr))))
>
> -#define _uatomic_sub_return(addr, v) _uatomic_add_return((addr), -(v))
> -
> -/* uatomic_add, uatomic_sub */
> +/* uatomic_add */
>
> static inline __attribute__((always_inline))
> void __uatomic_add(void *addr, unsigned long val, int len)
> @@ -297,8 +299,6 @@ void __uatomic_add(void *addr, unsigned long val, int len)
> #define _uatomic_add(addr, v) \
> (__uatomic_add((addr), (unsigned long)(v), sizeof(*(addr))))
>
> -#define _uatomic_sub(addr, v) _uatomic_add((addr), -(v))
> -
>
> /* uatomic_inc */
>
> @@ -449,24 +449,17 @@ extern unsigned long _compat_uatomic_xchg(void *addr,
> (unsigned long)(v), \
> sizeof(*(addr))))
>
> -#define compat_uatomic_sub_return(addr, v) \
> - compat_uatomic_add_return((addr), -(v))
> #define compat_uatomic_add(addr, v) \
> ((void)compat_uatomic_add_return((addr), (v)))
> -#define compat_uatomic_sub(addr, v) \
> - ((void)compat_uatomic_sub_return((addr), (v)))
> #define compat_uatomic_inc(addr) \
> (compat_uatomic_add((addr), 1))
> #define compat_uatomic_dec(addr) \
> - (compat_uatomic_sub((addr), 1))
> + (compat_uatomic_add((addr), -1))
>
> #else
> #define UATOMIC_COMPAT(insn) (_uatomic_##insn)
> #endif
>
> -/* Read is atomic even in compat mode */
We could say:
/* Read is atomic even in compat mode. Use generic version. */
> -#define uatomic_read(addr) _uatomic_read(addr)
> -
> #define uatomic_set(addr, v) \
> UATOMIC_COMPAT(set(addr, v))
> #define uatomic_cmpxchg(addr, old, _new) \
> @@ -475,10 +468,7 @@ extern unsigned long _compat_uatomic_xchg(void *addr,
> UATOMIC_COMPAT(xchg(addr, v))
> #define uatomic_add_return(addr, v) \
> UATOMIC_COMPAT(add_return(addr, v))
> -#define uatomic_sub_return(addr, v) \
> - UATOMIC_COMPAT(sub_return(addr, v))
> #define uatomic_add(addr, v) UATOMIC_COMPAT(add(addr, v))
> -#define uatomic_sub(addr, v) UATOMIC_COMPAT(sub(addr, v))
> #define uatomic_inc(addr) UATOMIC_COMPAT(inc(addr))
> #define uatomic_dec(addr) UATOMIC_COMPAT(dec(addr))
>
> @@ -486,4 +476,6 @@ extern unsigned long _compat_uatomic_xchg(void *addr,
> }
> #endif
>
> +#include <urcu/uatomic_defaults.h>
> +
> #endif /* _URCU_ARCH_UATOMIC_X86_H */
> diff --git a/urcu/uatomic_defaults.h b/urcu/uatomic_defaults.h
> new file mode 100644
> index 0000000..93467dd
> --- /dev/null
> +++ b/urcu/uatomic_defaults.h
> @@ -0,0 +1,262 @@
> +#ifndef _URCU_UATOMIC_GCC_H
> +#define _URCU_UATOMIC_GCC_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 Paolo Bonzini
> + *
> + * 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
> +
> +#ifndef BITS_PER_LONG
> +#define BITS_PER_LONG (__SIZEOF_LONG__ * 8)
> +#endif
> +
> +#ifndef uatomic_set
> +#define uatomic_set(addr, v) STORE_SHARED(*(addr), (v))
> +#endif
> +
> +#ifndef uatomic_read
> +#define uatomic_read(addr) LOAD_SHARED(*(addr))
> +#endif
> +
> +#if !defined __OPTIMIZE__ || defined UATOMIC_NO_LINK_ERROR
> +static inline __attribute__((always_inline))
> +void _uatomic_link_error()
> +{
> +#ifdef ILLEGAL_INSTR
> + /* generate an illegal instruction. Cannot catch this with linker tricks
> + * when optimizations are disabled. */
> + __asm__ __volatile__(ILLEGAL_INSTR);
> +#else
> + __builtin_trap ();
coding style:
__builtin_trap();
> +#endif
> +}
> +#else
> +extern void _uatomic_link_error ();
> +#endif
Please add comments after these nested #else and #endif to make it
easier to match the nesting.
e.g.
#ifdef A
#ifdef B
#else /* #ifdef B */
#endif /* #else #ifdef B */
#endif /* #ifdef A */
> +
> +/* cmpxchg */
> +
> +#ifndef uatomic_cmpxchg
> +static inline __attribute__((always_inline))
> +unsigned long _uatomic_cmpxchg(void *addr, unsigned long old,
> + unsigned long _new, int len)
> +{
> + switch (len) {
> + case 4:
> + return __sync_val_compare_and_swap_4(addr, old, _new);
> +#if (BITS_PER_LONG == 64)
> + case 8:
> + return __sync_val_compare_and_swap_8(addr, old, _new);
> +#endif
> + }
> + _uatomic_link_error();
> + return 0;
> +}
> +
> +
> +#define uatomic_cmpxchg(addr, old, _new) \
> + ((__typeof__(*(addr))) _uatomic_cmpxchg((addr), (unsigned long)(old),\
> + (unsigned long)(_new), \
> + sizeof(*(addr))))
> +
> +
> +/* uatomic_add_return */
> +
> +#ifndef uatomic_add_return
> +static inline __attribute__((always_inline))
> +unsigned long _uatomic_add_return(void *addr, unsigned long val,
> + int len)
> +{
> + switch (len) {
> + case 4:
> + return __sync_add_and_fetch_4(addr, val);
> +#if (BITS_PER_LONG == 64)
> + case 8:
> + return __sync_add_and_fetch_8(addr, val);
> +#endif
> + }
> + _uatomic_link_error();
> + return 0;
> +}
> +
> +
> +#define uatomic_add_return(addr, v) \
> + ((__typeof__(*(addr))) _uatomic_add_return((addr), \
> + (unsigned long)(v), \
> + sizeof(*(addr))))
> +#endif
> +
> +#ifndef uatomic_xchg
> +/* xchg */
> +
> +static inline __attribute__((always_inline))
> +unsigned long _uatomic_exchange(void *addr, unsigned long val, int len)
> +{
> + switch (len) {
> + case 4:
> + {
> + unsigned int old;
> +
> + do
> + old = uatomic_read((unsigned int *)addr);
> + while (!__sync_bool_compare_and_swap_4(addr, old, val));
I really prefer
do {
one liner;
} while (cond);
for some reason. (less error prone)
> +
> + return old;
> + }
> +#if (BITS_PER_LONG == 64)
> + case 8:
> + {
> + unsigned long old;
> +
> + do
> + old = uatomic_read((unsigned long *)addr);
> + while (!__sync_bool_compare_and_swap_8(addr, old, val));
> +
Same here.
> + return old;
> + }
> +#endif
> + }
> + _uatomic_link_error();
> + return 0;
> +}
> +
> +#define uatomic_xchg(addr, v) \
> + ((__typeof__(*(addr))) _uatomic_exchange((addr), (unsigned long)(v), \
> + sizeof(*(addr))))
> +#endif
> +
> +#else
#else ...
Thanks,
Mathieu
> +
> +#ifndef uatomic_add_return
> +/* uatomic_add_return */
> +
> +static inline __attribute__((always_inline))
> +unsigned long _uatomic_add_return(void *addr, unsigned long val, int len)
> +{
> + switch (len) {
> + case 4:
> + {
> + unsigned int old, oldt;
> +
> + oldt = uatomic_read((unsigned int *)addr);
> + do {
> + old = oldt;
> + oldt = _uatomic_cmpxchg(addr, old, old + val, 4);
> + } while (oldt != old);
> +
> + return old + val;
> + }
> +#if (BITS_PER_LONG == 64)
> + case 8:
> + {
> + unsigned long old, oldt;
> +
> + oldt = uatomic_read((unsigned long *)addr);
> + do {
> + old = oldt;
> + oldt = _uatomic_cmpxchg(addr, old, old + val, 8);
> + } while (oldt != old);
> +
> + return old + val;
> + }
> +#endif
> + }
> + _uatomic_link_error();
> + return 0;
> +}
> +
> +#define uatomic_add_return(addr, v) \
> + ((__typeof__(*(addr))) _uatomic_add_return((addr), \
> + (unsigned long)(v), \
> + sizeof(*(addr))))
> +#endif
> +
> +#ifndef uatomic_xchg
> +/* xchg */
> +
> +static inline __attribute__((always_inline))
> +unsigned long _uatomic_exchange(void *addr, unsigned long val, int len)
> +{
> + switch (len) {
> + case 4:
> + {
> + unsigned int old, oldt;
> +
> + oldt = uatomic_read((unsigned int *)addr);
> + do {
> + old = oldt;
> + oldt = _uatomic_cmpxchg(addr, old, val, 4);
> + } while (oldt != old);
> +
> + return old;
> + }
> +#if (BITS_PER_LONG == 64)
> + case 8:
> + {
> + unsigned long old, oldt;
> +
> + oldt = uatomic_read((unsigned long *)addr);
> + do {
> + old = oldt;
> + oldt = _uatomic_cmpxchg(addr, old, val, 8);
> + } while (oldt != old);
> +
> + return old;
> + }
> +#endif
> + }
> + _uatomic_link_error();
> + return 0;
> +}
> +
> +#define uatomic_xchg(addr, v) \
> + ((__typeof__(*(addr))) _uatomic_exchange((addr), (unsigned long)(v), \
> + sizeof(*(addr))))
> +#endif
> +
> +#endif
> +
> +/* uatomic_sub_return, uatomic_add, uatomic_sub, uatomic_inc, uatomic_dec */
> +
> +#ifndef uatomic_add
> +#define uatomic_add(addr, v) (void)uatomic_add_return((addr), (v))
> +#endif
> +
> +#define uatomic_sub_return(addr, v) uatomic_add_return((addr), -(v))
> +#define uatomic_sub(addr, v) uatomic_add((addr), -(v))
> +
> +#ifndef uatomic_inc
> +#define uatomic_inc(addr) uatomic_add((addr), 1)
> +#endif
> +
> +#ifndef uatomic_dec
> +#define uatomic_dec(addr) uatomic_add((addr), -1)
> +#endif
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* _URCU_UATOMIC_GCC_H */
> --
> 1.6.6
>
>
>
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>
--
Mathieu Desnoyers
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