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my_atomic.h
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my_atomic.h
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#ifndef MY_ATOMIC_INCLUDED
#define MY_ATOMIC_INCLUDED
/* Copyright (C) 2006 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/*
This header defines five atomic operations:
my_atomic_add#(&var, what)
'Fetch and Add'
add 'what' to *var, and return the old value of *var
my_atomic_fas#(&var, what)
'Fetch And Store'
store 'what' in *var, and return the old value of *var
my_atomic_cas#(&var, &old, new)
An odd variation of 'Compare And Set/Swap'
if *var is equal to *old, then store 'new' in *var, and return TRUE
otherwise store *var in *old, and return FALSE
Usually, &old should not be accessed if the operation is successful.
my_atomic_load#(&var)
return *var
my_atomic_store#(&var, what)
store 'what' in *var
'#' is substituted by a size suffix - 8, 16, 32, 64, or ptr
(e.g. my_atomic_add8, my_atomic_fas32, my_atomic_casptr).
NOTE This operations are not always atomic, so they always must be
enclosed in my_atomic_rwlock_rdlock(lock)/my_atomic_rwlock_rdunlock(lock)
or my_atomic_rwlock_wrlock(lock)/my_atomic_rwlock_wrunlock(lock).
Hint: if a code block makes intensive use of atomic ops, it make sense
to take/release rwlock once for the whole block, not for every statement.
On architectures where these operations are really atomic, rwlocks will
be optimized away.
8- and 16-bit atomics aren't implemented for windows (see generic-msvc.h),
but can be added, if necessary.
*/
#ifndef my_atomic_rwlock_init
#define intptr void *
/**
Currently we don't support 8-bit and 16-bit operations.
It can be added later if needed.
*/
#undef MY_ATOMIC_HAS_8_16
#ifndef MY_ATOMIC_MODE_RWLOCKS
/*
* Attempt to do atomic ops without locks
*/
#include "atomic/nolock.h"
#endif
#ifndef make_atomic_cas_body
/* nolock.h was not able to generate even a CAS function, fall back */
#include "atomic/rwlock.h"
#endif
/* define missing functions by using the already generated ones */
#ifndef make_atomic_add_body
#define make_atomic_add_body(S) \
int ## S tmp=*a; \
while (!my_atomic_cas ## S(a, &tmp, tmp+v)) ; \
v=tmp;
#endif
#ifndef make_atomic_fas_body
#define make_atomic_fas_body(S) \
int ## S tmp=*a; \
while (!my_atomic_cas ## S(a, &tmp, v)) ; \
v=tmp;
#endif
#ifndef make_atomic_load_body
#define make_atomic_load_body(S) \
ret= 0; /* avoid compiler warning */ \
(void)(my_atomic_cas ## S(a, &ret, ret));
#endif
#ifndef make_atomic_store_body
#define make_atomic_store_body(S) \
(void)(my_atomic_fas ## S (a, v));
#endif
/*
transparent_union doesn't work in g++
Bug ?
Darwin's gcc doesn't want to put pointers in a transparent_union
when built with -arch ppc64. Complains:
warning: 'transparent_union' attribute ignored
*/
#if defined(__GNUC__) && !defined(__cplusplus) && \
! (defined(__APPLE__) && (defined(_ARCH_PPC64) ||defined (_ARCH_PPC)))
/*
we want to be able to use my_atomic_xxx functions with
both signed and unsigned integers. But gcc will issue a warning
"passing arg N of `my_atomic_XXX' as [un]signed due to prototype"
if the signedness of the argument doesn't match the prototype, or
"pointer targets in passing argument N of my_atomic_XXX differ in signedness"
if int* is used where uint* is expected (or vice versa).
Let's shut these warnings up
*/
#define make_transparent_unions(S) \
typedef union { \
int ## S i; \
uint ## S u; \
} U_ ## S __attribute__ ((transparent_union)); \
typedef union { \
int ## S volatile *i; \
uint ## S volatile *u; \
} Uv_ ## S __attribute__ ((transparent_union));
#define uintptr intptr
make_transparent_unions(8)
make_transparent_unions(16)
make_transparent_unions(32)
make_transparent_unions(64)
make_transparent_unions(ptr)
#undef uintptr
#undef make_transparent_unions
#define a U_a.i
#define cmp U_cmp.i
#define v U_v.i
#define set U_set.i
#else
#define U_8 int8
#define U_16 int16
#define U_32 int32
#define U_64 int64
#define U_ptr intptr
#define Uv_8 int8
#define Uv_16 int16
#define Uv_32 int32
#define Uv_64 int64
#define Uv_ptr intptr
#define U_a volatile *a
#define U_cmp *cmp
#define U_v v
#define U_set set
#endif /* __GCC__ transparent_union magic */
#define make_atomic_cas(S) \
static inline int my_atomic_cas ## S(Uv_ ## S U_a, \
Uv_ ## S U_cmp, U_ ## S U_set) \
{ \
int8 ret; \
make_atomic_cas_body(S); \
return ret; \
}
#define make_atomic_add(S) \
static inline int ## S my_atomic_add ## S( \
Uv_ ## S U_a, U_ ## S U_v) \
{ \
make_atomic_add_body(S); \
return v; \
}
#define make_atomic_fas(S) \
static inline int ## S my_atomic_fas ## S( \
Uv_ ## S U_a, U_ ## S U_v) \
{ \
make_atomic_fas_body(S); \
return v; \
}
#define make_atomic_load(S) \
static inline int ## S my_atomic_load ## S(Uv_ ## S U_a) \
{ \
int ## S ret; \
make_atomic_load_body(S); \
return ret; \
}
#define make_atomic_store(S) \
static inline void my_atomic_store ## S( \
Uv_ ## S U_a, U_ ## S U_v) \
{ \
make_atomic_store_body(S); \
}
#ifdef MY_ATOMIC_HAS_8_16
make_atomic_cas(8)
make_atomic_cas(16)
#endif
make_atomic_cas(32)
make_atomic_cas(64)
make_atomic_cas(ptr)
#ifdef MY_ATOMIC_HAS_8_16
make_atomic_add(8)
make_atomic_add(16)
#endif
make_atomic_add(32)
make_atomic_add(64)
#ifdef MY_ATOMIC_HAS_8_16
make_atomic_load(8)
make_atomic_load(16)
#endif
make_atomic_load(32)
make_atomic_load(64)
make_atomic_load(ptr)
#ifdef MY_ATOMIC_HAS_8_16
make_atomic_fas(8)
make_atomic_fas(16)
#endif
make_atomic_fas(32)
make_atomic_fas(64)
make_atomic_fas(ptr)
#ifdef MY_ATOMIC_HAS_8_16
make_atomic_store(8)
make_atomic_store(16)
#endif
make_atomic_store(32)
make_atomic_store(64)
make_atomic_store(ptr)
#ifdef _atomic_h_cleanup_
#include _atomic_h_cleanup_
#undef _atomic_h_cleanup_
#endif
#undef U_8
#undef U_16
#undef U_32
#undef U_64
#undef U_ptr
#undef Uv_8
#undef Uv_16
#undef Uv_32
#undef Uv_64
#undef Uv_ptr
#undef a
#undef cmp
#undef v
#undef set
#undef U_a
#undef U_cmp
#undef U_v
#undef U_set
#undef make_atomic_add
#undef make_atomic_cas
#undef make_atomic_load
#undef make_atomic_store
#undef make_atomic_fas
#undef make_atomic_add_body
#undef make_atomic_cas_body
#undef make_atomic_load_body
#undef make_atomic_store_body
#undef make_atomic_fas_body
#undef intptr
/*
the macro below defines (as an expression) the code that
will be run in spin-loops. Intel manuals recummend to have PAUSE there.
It is expected to be defined in include/atomic/ *.h files
*/
#ifndef LF_BACKOFF
#define LF_BACKOFF (1)
#endif
#define MY_ATOMIC_OK 0
#define MY_ATOMIC_NOT_1CPU 1
extern int my_atomic_initialize();
#endif
#endif /* MY_ATOMIC_INCLUDED */