![Peter Zijlstra](/assets/img/avatar_default.png)
This patch makes sure that atomic_{read,set}() are at least {READ,WRITE}_ONCE(). We already had the 'requirement' that atomic_read() should use ACCESS_ONCE(), and most archs had this, but a few were lacking. All are now converted to use READ_ONCE(). And, by a symmetry and general paranoia argument, upgrade atomic_set() to use WRITE_ONCE(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: james.hogan@imgtec.com Cc: linux-kernel@vger.kernel.org Cc: oleg@redhat.com Cc: will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
200 lines
5 KiB
C
200 lines
5 KiB
C
/*
|
|
* Atomic operations that C can't guarantee us. Useful for
|
|
* resource counting etc.
|
|
*
|
|
* But use these as seldom as possible since they are slower than
|
|
* regular operations.
|
|
*
|
|
* Copyright (C) 2004-2006 Atmel Corporation
|
|
*
|
|
* 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_AVR32_ATOMIC_H
|
|
#define __ASM_AVR32_ATOMIC_H
|
|
|
|
#include <linux/types.h>
|
|
#include <asm/cmpxchg.h>
|
|
|
|
#define ATOMIC_INIT(i) { (i) }
|
|
|
|
#define atomic_read(v) READ_ONCE((v)->counter)
|
|
#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
|
|
|
|
#define ATOMIC_OP_RETURN(op, asm_op, asm_con) \
|
|
static inline int __atomic_##op##_return(int i, atomic_t *v) \
|
|
{ \
|
|
int result; \
|
|
\
|
|
asm volatile( \
|
|
"/* atomic_" #op "_return */\n" \
|
|
"1: ssrf 5\n" \
|
|
" ld.w %0, %2\n" \
|
|
" " #asm_op " %0, %3\n" \
|
|
" stcond %1, %0\n" \
|
|
" brne 1b" \
|
|
: "=&r" (result), "=o" (v->counter) \
|
|
: "m" (v->counter), #asm_con (i) \
|
|
: "cc"); \
|
|
\
|
|
return result; \
|
|
}
|
|
|
|
ATOMIC_OP_RETURN(sub, sub, rKs21)
|
|
ATOMIC_OP_RETURN(add, add, r)
|
|
|
|
#define ATOMIC_OP(op, asm_op) \
|
|
ATOMIC_OP_RETURN(op, asm_op, r) \
|
|
static inline void atomic_##op(int i, atomic_t *v) \
|
|
{ \
|
|
(void)__atomic_##op##_return(i, v); \
|
|
}
|
|
|
|
ATOMIC_OP(and, and)
|
|
ATOMIC_OP(or, or)
|
|
ATOMIC_OP(xor, eor)
|
|
|
|
#undef ATOMIC_OP
|
|
#undef ATOMIC_OP_RETURN
|
|
|
|
/*
|
|
* Probably found the reason why we want to use sub with the signed 21-bit
|
|
* limit, it uses one less register than the add instruction that can add up to
|
|
* 32-bit values.
|
|
*
|
|
* Both instructions are 32-bit, to use a 16-bit instruction the immediate is
|
|
* very small; 4 bit.
|
|
*
|
|
* sub 32-bit, type IV, takes a register and subtracts a 21-bit immediate.
|
|
* add 32-bit, type II, adds two register values together.
|
|
*/
|
|
#define IS_21BIT_CONST(i) \
|
|
(__builtin_constant_p(i) && ((i) >= -1048575) && ((i) <= 1048576))
|
|
|
|
/*
|
|
* atomic_add_return - add integer to atomic variable
|
|
* @i: integer value to add
|
|
* @v: pointer of type atomic_t
|
|
*
|
|
* Atomically adds @i to @v. Returns the resulting value.
|
|
*/
|
|
static inline int atomic_add_return(int i, atomic_t *v)
|
|
{
|
|
if (IS_21BIT_CONST(i))
|
|
return __atomic_sub_return(-i, v);
|
|
|
|
return __atomic_add_return(i, v);
|
|
}
|
|
|
|
/*
|
|
* atomic_sub_return - subtract the atomic variable
|
|
* @i: integer value to subtract
|
|
* @v: pointer of type atomic_t
|
|
*
|
|
* Atomically subtracts @i from @v. Returns the resulting value.
|
|
*/
|
|
static inline int atomic_sub_return(int i, atomic_t *v)
|
|
{
|
|
if (IS_21BIT_CONST(i))
|
|
return __atomic_sub_return(i, v);
|
|
|
|
return __atomic_add_return(-i, v);
|
|
}
|
|
|
|
/*
|
|
* __atomic_add_unless - add unless the number is a given value
|
|
* @v: pointer of type atomic_t
|
|
* @a: the amount to add to v...
|
|
* @u: ...unless v is equal to u.
|
|
*
|
|
* Atomically adds @a to @v, so long as it was not @u.
|
|
* Returns the old value of @v.
|
|
*/
|
|
static inline int __atomic_add_unless(atomic_t *v, int a, int u)
|
|
{
|
|
int tmp, old = atomic_read(v);
|
|
|
|
if (IS_21BIT_CONST(a)) {
|
|
asm volatile(
|
|
"/* __atomic_sub_unless */\n"
|
|
"1: ssrf 5\n"
|
|
" ld.w %0, %2\n"
|
|
" cp.w %0, %4\n"
|
|
" breq 1f\n"
|
|
" sub %0, %3\n"
|
|
" stcond %1, %0\n"
|
|
" brne 1b\n"
|
|
"1:"
|
|
: "=&r"(tmp), "=o"(v->counter)
|
|
: "m"(v->counter), "rKs21"(-a), "rKs21"(u)
|
|
: "cc", "memory");
|
|
} else {
|
|
asm volatile(
|
|
"/* __atomic_add_unless */\n"
|
|
"1: ssrf 5\n"
|
|
" ld.w %0, %2\n"
|
|
" cp.w %0, %4\n"
|
|
" breq 1f\n"
|
|
" add %0, %3\n"
|
|
" stcond %1, %0\n"
|
|
" brne 1b\n"
|
|
"1:"
|
|
: "=&r"(tmp), "=o"(v->counter)
|
|
: "m"(v->counter), "r"(a), "ir"(u)
|
|
: "cc", "memory");
|
|
}
|
|
|
|
return old;
|
|
}
|
|
|
|
#undef IS_21BIT_CONST
|
|
|
|
/*
|
|
* atomic_sub_if_positive - conditionally subtract integer from atomic variable
|
|
* @i: integer value to subtract
|
|
* @v: pointer of type atomic_t
|
|
*
|
|
* Atomically test @v and subtract @i if @v is greater or equal than @i.
|
|
* The function returns the old value of @v minus @i.
|
|
*/
|
|
static inline int atomic_sub_if_positive(int i, atomic_t *v)
|
|
{
|
|
int result;
|
|
|
|
asm volatile(
|
|
"/* atomic_sub_if_positive */\n"
|
|
"1: ssrf 5\n"
|
|
" ld.w %0, %2\n"
|
|
" sub %0, %3\n"
|
|
" brlt 1f\n"
|
|
" stcond %1, %0\n"
|
|
" brne 1b\n"
|
|
"1:"
|
|
: "=&r"(result), "=o"(v->counter)
|
|
: "m"(v->counter), "ir"(i)
|
|
: "cc", "memory");
|
|
|
|
return result;
|
|
}
|
|
|
|
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
|
|
#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
|
|
|
|
#define atomic_sub(i, v) (void)atomic_sub_return(i, v)
|
|
#define atomic_add(i, v) (void)atomic_add_return(i, v)
|
|
#define atomic_dec(v) atomic_sub(1, (v))
|
|
#define atomic_inc(v) atomic_add(1, (v))
|
|
|
|
#define atomic_dec_return(v) atomic_sub_return(1, v)
|
|
#define atomic_inc_return(v) atomic_add_return(1, v)
|
|
|
|
#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)
|
|
#define atomic_inc_and_test(v) (atomic_add_return(1, v) == 0)
|
|
#define atomic_dec_and_test(v) (atomic_sub_return(1, v) == 0)
|
|
#define atomic_add_negative(i, v) (atomic_add_return(i, v) < 0)
|
|
|
|
#define atomic_dec_if_positive(v) atomic_sub_if_positive(1, v)
|
|
|
|
#endif /* __ASM_AVR32_ATOMIC_H */
|