Commit 8426e1f6 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

[PATCH] atomic: inc_not_zero



Introduce an atomic_inc_not_zero operation.  Make this a special case of
atomic_add_unless because lockless pagecache actually wants
atomic_inc_not_negativeone due to its offset refcount.
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4a6dae6d
......@@ -115,7 +115,7 @@ boolean is return which indicates whether the resulting counter value
is negative. It requires explicit memory barrier semantics around the
operation.
Finally:
Then:
int atomic_cmpxchg(atomic_t *v, int old, int new);
......@@ -129,6 +129,18 @@ atomic_cmpxchg requires explicit memory barriers around the operation.
The semantics for atomic_cmpxchg are the same as those defined for 'cas'
below.
Finally:
int atomic_add_unless(atomic_t *v, int a, int u);
If the atomic value v is not equal to u, this function adds a to v, and
returns non zero. If v is equal to u then it returns zero. This is done as
an atomic operation.
atomic_add_unless requires explicit memory barriers around the operation.
atomic_inc_not_zero, equivalent to atomic_add_unless(v, 1, 0)
If a caller requires memory barrier semantics around an atomic_t
operation which does not return a value, a set of interfaces are
......
......@@ -53,6 +53,21 @@ int atomic_cmpxchg(atomic_t *v, int old, int new)
return ret;
}
int atomic_add_unless(atomic_t *v, int a, int u)
{
int ret;
unsigned long flags;
spin_lock_irqsave(ATOMIC_HASH(v), flags);
ret = v->counter;
if (ret != u)
v->counter += a;
spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
return ret != u;
}
static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
/* Atomic operations are already serializing */
void atomic_set(atomic_t *v, int i)
{
unsigned long flags;
......
......@@ -179,6 +179,16 @@ static __inline__ long atomic64_sub_return(long i, atomic64_t * v)
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_dec_return(v) atomic_sub_return(1,(v))
#define atomic64_dec_return(v) atomic64_sub_return(1,(v))
......
......@@ -173,6 +173,17 @@ static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
#endif /* __LINUX_ARM_ARCH__ */
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
int c, old;
c = atomic_read(v);
while (c != u && (old = atomic_cmpxchg((v), c, c + a)) != c)
c = old;
return c != u;
}
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_add(i, v) (void) atomic_add_return(i, v)
#define atomic_inc(v) (void) atomic_add_return(1, v)
#define atomic_sub(i, v) (void) atomic_sub_return(i, v)
......
......@@ -76,6 +76,21 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
return ret;
}
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
int ret;
unsigned long flags;
local_irq_save(flags);
ret = v->counter;
if (ret != u)
v->counter += a;
local_irq_restore(flags);
return ret != u;
}
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
{
unsigned long flags;
......
......@@ -136,6 +136,20 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
return ret;
}
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
int ret;
unsigned long flags;
cris_atomic_save(v, flags);
ret = v->counter;
if (ret != u)
v->counter += a;
cris_atomic_restore(v, flags);
return ret != u;
}
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
/* Atomic operations are already serializing */
#define smp_mb__before_atomic_dec() barrier()
#define smp_mb__after_atomic_dec() barrier()
......
......@@ -416,4 +416,14 @@ extern uint32_t __cmpxchg_32(uint32_t *v, uint32_t test, uint32_t new);
#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#endif /* _ASM_ATOMIC_H */
......@@ -95,6 +95,20 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
return ret;
}
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
int ret;
unsigned long flags;
local_irq_save(flags);
ret = v->counter;
if (ret != u)
v->counter += a;
local_irq_restore(flags);
return ret != u;
}
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
static __inline__ void atomic_clear_mask(unsigned long mask, unsigned long *v)
{
__asm__ __volatile__("stc ccr,r1l\n\t"
......
......@@ -217,6 +217,25 @@ static __inline__ int atomic_sub_return(int i, atomic_t *v)
#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
/**
* 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 non-zero if @v was not @u, and zero otherwise.
*/
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_inc_return(v) (atomic_add_return(1,v))
#define atomic_dec_return(v) (atomic_sub_return(1,v))
......
......@@ -90,6 +90,16 @@ ia64_atomic64_sub (__s64 i, atomic64_t *v)
#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_add_return(i,v) \
({ \
int __ia64_aar_i = (i); \
......
......@@ -141,6 +141,16 @@ static inline void atomic_set_mask(unsigned long mask, unsigned long *v)
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
/* Atomic operations are already serializing */
#define smp_mb__before_atomic_dec() barrier()
#define smp_mb__after_atomic_dec() barrier()
......
......@@ -130,6 +130,16 @@ static inline int atomic_sub_return(int i, atomic_t * v)
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_dec_return(v) atomic_sub_return(1,(v))
#define atomic_inc_return(v) atomic_add_return(1,(v))
......
......@@ -289,6 +289,25 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v)
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
/**
* 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 non-zero if @v was not @u, and zero otherwise.
*/
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_dec_return(v) atomic_sub_return(1,(v))
#define atomic_inc_return(v) atomic_add_return(1,(v))
......
......@@ -166,6 +166,25 @@ static __inline__ int atomic_read(const atomic_t *v)
/* exported interface */
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
/**
* 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 non-zero if @v was not @u, and zero otherwise.
*/
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_add(i,v) ((void)(__atomic_add_return( ((int)i),(v))))
#define atomic_sub(i,v) ((void)(__atomic_add_return(-((int)i),(v))))
#define atomic_inc(v) ((void)(__atomic_add_return( 1,(v))))
......
......@@ -166,6 +166,31 @@ static __inline__ int atomic_dec_return(atomic_t *v)
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
/**
* 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 non-zero if @v was not @u, and zero otherwise.
*/
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
for (;;) { \
if (unlikely(c == (u))) \
break; \
old = atomic_cmpxchg((v), c, c + (a)); \
if (likely(old == c)) \
break; \
c = old; \
} \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_sub_and_test(a, v) (atomic_sub_return((a), (v)) == 0)
#define atomic_dec_and_test(v) (atomic_dec_return((v)) == 0)
......
......@@ -200,6 +200,16 @@ atomic_compare_and_swap(int expected_oldval,int new_val,atomic_t *v)
#define atomic_cmpxchg(v, o, n) (atomic_compare_and_swap((o), (n), &((v)->counter)))
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define smp_mb__before_atomic_dec() smp_mb()
#define smp_mb__after_atomic_dec() smp_mb()
#define smp_mb__before_atomic_inc() smp_mb()
......
......@@ -101,6 +101,21 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
return ret;
}
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
int ret;
unsigned long flags;
local_irq_save(flags);
ret = v->counter;
if (ret != u)
v->counter += a;
local_irq_restore(flags);
return ret != u;
}
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
static __inline__ void atomic_clear_mask(unsigned int mask, atomic_t *v)
{
unsigned long flags;
......
......@@ -113,6 +113,21 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
return ret;
}
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
int ret;
unsigned long flags;
local_irq_save(flags);
ret = v->counter;
if (ret != u)
v->counter += a;
local_irq_restore(flags);
return ret != u;
}
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
static __inline__ void atomic_clear_mask(unsigned int mask, atomic_t *v)
{
unsigned long flags;
......
......@@ -20,6 +20,7 @@ typedef struct { volatile int counter; } atomic_t;
extern int __atomic_add_return(int, atomic_t *);
extern int atomic_cmpxchg(atomic_t *, int, int);
extern int atomic_add_unless(atomic_t *, int, int);
extern void atomic_set(atomic_t *, int);
#define atomic_read(v) ((v)->counter)
......@@ -49,6 +50,8 @@ extern void atomic_set(atomic_t *, int);
#define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
/* This is the old 24-bit implementation. It's still used internally
* by some sparc-specific code, notably the semaphore implementation.
*/
......
......@@ -72,6 +72,16 @@ extern int atomic64_sub_ret(int, atomic64_t *);
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
#define atomic_add_unless(v, a, u) \
({ \
int c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
/* Atomic operations are already serializing */
#ifdef CONFIG_SMP
#define smp_mb__before_atomic_dec() membar_storeload_loadload();
......
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