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linux-next/arch/x86/include/asm/atomic64_64.h
Peter Zijlstra 69d927bba3 x86/atomic: Fix smp_mb__{before,after}_atomic()
Recent probing at the Linux Kernel Memory Model uncovered a
'surprise'. Strongly ordered architectures where the atomic RmW
primitive implies full memory ordering and
smp_mb__{before,after}_atomic() are a simple barrier() (such as x86)
fail for:

	*x = 1;
	atomic_inc(u);
	smp_mb__after_atomic();
	r0 = *y;

Because, while the atomic_inc() implies memory order, it
(surprisingly) does not provide a compiler barrier. This then allows
the compiler to re-order like so:

	atomic_inc(u);
	*x = 1;
	smp_mb__after_atomic();
	r0 = *y;

Which the CPU is then allowed to re-order (under TSO rules) like:

	atomic_inc(u);
	r0 = *y;
	*x = 1;

And this very much was not intended. Therefore strengthen the atomic
RmW ops to include a compiler barrier.

NOTE: atomic_{or,and,xor} and the bitops already had the compiler
barrier.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-06-17 12:09:59 +02:00

246 lines
5.8 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_ATOMIC64_64_H
#define _ASM_X86_ATOMIC64_64_H
#include <linux/types.h>
#include <asm/alternative.h>
#include <asm/cmpxchg.h>
/* The 64-bit atomic type */
#define ATOMIC64_INIT(i) { (i) }
/**
* arch_atomic64_read - read atomic64 variable
* @v: pointer of type atomic64_t
*
* Atomically reads the value of @v.
* Doesn't imply a read memory barrier.
*/
static inline s64 arch_atomic64_read(const atomic64_t *v)
{
return READ_ONCE((v)->counter);
}
/**
* arch_atomic64_set - set atomic64 variable
* @v: pointer to type atomic64_t
* @i: required value
*
* Atomically sets the value of @v to @i.
*/
static inline void arch_atomic64_set(atomic64_t *v, s64 i)
{
WRITE_ONCE(v->counter, i);
}
/**
* arch_atomic64_add - add integer to atomic64 variable
* @i: integer value to add
* @v: pointer to type atomic64_t
*
* Atomically adds @i to @v.
*/
static __always_inline void arch_atomic64_add(s64 i, atomic64_t *v)
{
asm volatile(LOCK_PREFIX "addq %1,%0"
: "=m" (v->counter)
: "er" (i), "m" (v->counter) : "memory");
}
/**
* arch_atomic64_sub - subtract the atomic64 variable
* @i: integer value to subtract
* @v: pointer to type atomic64_t
*
* Atomically subtracts @i from @v.
*/
static inline void arch_atomic64_sub(s64 i, atomic64_t *v)
{
asm volatile(LOCK_PREFIX "subq %1,%0"
: "=m" (v->counter)
: "er" (i), "m" (v->counter) : "memory");
}
/**
* arch_atomic64_sub_and_test - subtract value from variable and test result
* @i: integer value to subtract
* @v: pointer to type atomic64_t
*
* Atomically subtracts @i from @v and returns
* true if the result is zero, or false for all
* other cases.
*/
static inline bool arch_atomic64_sub_and_test(s64 i, atomic64_t *v)
{
return GEN_BINARY_RMWcc(LOCK_PREFIX "subq", v->counter, e, "er", i);
}
#define arch_atomic64_sub_and_test arch_atomic64_sub_and_test
/**
* arch_atomic64_inc - increment atomic64 variable
* @v: pointer to type atomic64_t
*
* Atomically increments @v by 1.
*/
static __always_inline void arch_atomic64_inc(atomic64_t *v)
{
asm volatile(LOCK_PREFIX "incq %0"
: "=m" (v->counter)
: "m" (v->counter) : "memory");
}
#define arch_atomic64_inc arch_atomic64_inc
/**
* arch_atomic64_dec - decrement atomic64 variable
* @v: pointer to type atomic64_t
*
* Atomically decrements @v by 1.
*/
static __always_inline void arch_atomic64_dec(atomic64_t *v)
{
asm volatile(LOCK_PREFIX "decq %0"
: "=m" (v->counter)
: "m" (v->counter) : "memory");
}
#define arch_atomic64_dec arch_atomic64_dec
/**
* arch_atomic64_dec_and_test - decrement and test
* @v: pointer to type atomic64_t
*
* Atomically decrements @v by 1 and
* returns true if the result is 0, or false for all other
* cases.
*/
static inline bool arch_atomic64_dec_and_test(atomic64_t *v)
{
return GEN_UNARY_RMWcc(LOCK_PREFIX "decq", v->counter, e);
}
#define arch_atomic64_dec_and_test arch_atomic64_dec_and_test
/**
* arch_atomic64_inc_and_test - increment and test
* @v: pointer to type atomic64_t
*
* Atomically increments @v by 1
* and returns true if the result is zero, or false for all
* other cases.
*/
static inline bool arch_atomic64_inc_and_test(atomic64_t *v)
{
return GEN_UNARY_RMWcc(LOCK_PREFIX "incq", v->counter, e);
}
#define arch_atomic64_inc_and_test arch_atomic64_inc_and_test
/**
* arch_atomic64_add_negative - add and test if negative
* @i: integer value to add
* @v: pointer to type atomic64_t
*
* Atomically adds @i to @v and returns true
* if the result is negative, or false when
* result is greater than or equal to zero.
*/
static inline bool arch_atomic64_add_negative(s64 i, atomic64_t *v)
{
return GEN_BINARY_RMWcc(LOCK_PREFIX "addq", v->counter, s, "er", i);
}
#define arch_atomic64_add_negative arch_atomic64_add_negative
/**
* arch_atomic64_add_return - add and return
* @i: integer value to add
* @v: pointer to type atomic64_t
*
* Atomically adds @i to @v and returns @i + @v
*/
static __always_inline s64 arch_atomic64_add_return(s64 i, atomic64_t *v)
{
return i + xadd(&v->counter, i);
}
static inline s64 arch_atomic64_sub_return(s64 i, atomic64_t *v)
{
return arch_atomic64_add_return(-i, v);
}
static inline s64 arch_atomic64_fetch_add(s64 i, atomic64_t *v)
{
return xadd(&v->counter, i);
}
static inline s64 arch_atomic64_fetch_sub(s64 i, atomic64_t *v)
{
return xadd(&v->counter, -i);
}
static inline s64 arch_atomic64_cmpxchg(atomic64_t *v, s64 old, s64 new)
{
return arch_cmpxchg(&v->counter, old, new);
}
#define arch_atomic64_try_cmpxchg arch_atomic64_try_cmpxchg
static __always_inline bool arch_atomic64_try_cmpxchg(atomic64_t *v, s64 *old, s64 new)
{
return try_cmpxchg(&v->counter, old, new);
}
static inline s64 arch_atomic64_xchg(atomic64_t *v, s64 new)
{
return arch_xchg(&v->counter, new);
}
static inline void arch_atomic64_and(s64 i, atomic64_t *v)
{
asm volatile(LOCK_PREFIX "andq %1,%0"
: "+m" (v->counter)
: "er" (i)
: "memory");
}
static inline s64 arch_atomic64_fetch_and(s64 i, atomic64_t *v)
{
s64 val = arch_atomic64_read(v);
do {
} while (!arch_atomic64_try_cmpxchg(v, &val, val & i));
return val;
}
static inline void arch_atomic64_or(s64 i, atomic64_t *v)
{
asm volatile(LOCK_PREFIX "orq %1,%0"
: "+m" (v->counter)
: "er" (i)
: "memory");
}
static inline s64 arch_atomic64_fetch_or(s64 i, atomic64_t *v)
{
s64 val = arch_atomic64_read(v);
do {
} while (!arch_atomic64_try_cmpxchg(v, &val, val | i));
return val;
}
static inline void arch_atomic64_xor(s64 i, atomic64_t *v)
{
asm volatile(LOCK_PREFIX "xorq %1,%0"
: "+m" (v->counter)
: "er" (i)
: "memory");
}
static inline s64 arch_atomic64_fetch_xor(s64 i, atomic64_t *v)
{
s64 val = arch_atomic64_read(v);
do {
} while (!arch_atomic64_try_cmpxchg(v, &val, val ^ i));
return val;
}
#endif /* _ASM_X86_ATOMIC64_64_H */