[PATCH 20/20] arch: Rewrite generic atomic support
From: Peter Zijlstra
Date: Thu May 08 2014 - 10:06:46 EST
Rewrite generic atomic support to only require cmpxchg(), generate all
other primitives from that.
Furthermore reduce the endless repetition for all these primitives to
a few CPP macros. This way we get more for less lines.
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
include/asm-generic/atomic.h | 174 ++++++++++++++++++-----------------------
include/asm-generic/atomic64.h | 20 +++-
lib/atomic64.c | 83 ++++++++-----------
3 files changed, 130 insertions(+), 147 deletions(-)
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -19,13 +19,81 @@
#include <asm/barrier.h>
#ifdef CONFIG_SMP
-/* Force people to define core atomics */
-# if !defined(atomic_add_return) || !defined(atomic_sub_return) || \
- !defined(atomic_clear_mask) || !defined(atomic_set_mask)
-# error "SMP requires a little arch-specific magic"
-# endif
+
+/* we can build all atomic primitives from cmpxchg */
+
+#define ATOMIC_OP(op, c_op) \
+static inline void atomic_##op(int i, atomic_t *v) \
+{ \
+ int c, old; \
+ \
+ c = v->counter; \
+ while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
+ c = old; \
+}
+
+#define ATOMIC_OP_RETURN(op, c_op) \
+static inline int atomic_##op##_return(int i, atomic_t *v) \
+{ \
+ int c, old; \
+ \
+ c = v->counter; \
+ while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
+ c = old; \
+ \
+ return c c_op i; \
+}
+
+#else
+
+#include <linux/irqflags.h>
+
+#define ATOMIC_OP(op, c_op) \
+static inline void atomic_##op(int i, atomic_t *v) \
+{ \
+ unsigned long flags; \
+ \
+ raw_local_irq_save(flags); \
+ v->counter c_op i; \
+ raw_local_irq_restore(flags); \
+}
+
+#define ATOMIC_OP_RETURN(op, c_op) \
+static inline int atomic_##op##_return(int i, atomic_t *v) \
+{ \
+ unsigned long flags; \
+ int ret; \
+ \
+ raw_local_irq_save(flags); \
+ ret = (v->counter c_op i); \
+ raw_local_irq_restore(flags); \
+ \
+ return ret; \
+}
+
+#endif /* CONFIG_SMP */
+
+#ifndef atomic_add_return
+ATOMIC_OP_RETURN(add, +)
+#endif
+
+#ifndef atomic_sub_return
+ATOMIC_OP_RETURN(sub, -)
+#endif
+
+#ifndef atomic_clear_mask
+ATOMIC_OP(and, &)
+#define atomic_clear_mask(i, v) atomic_and(~(i), (v))
+#endif
+
+#ifndef atomic_set_mask
+ATOMIC_OP(or, |)
+#define atomic_set_mask(i, v) atomic_or((i), (v))
#endif
+#undef ATOMIC_OP_RETURN
+#undef ATOMIC_OP
+
/*
* Atomic operations that C can't guarantee us. Useful for
* resource counting etc..
@@ -33,8 +101,6 @@
#define ATOMIC_INIT(i) { (i) }
-#ifdef __KERNEL__
-
/**
* atomic_read - read atomic variable
* @v: pointer of type atomic_t
@@ -56,52 +122,6 @@
#include <linux/irqflags.h>
-/**
- * atomic_add_return - add integer to atomic variable
- * @i: integer value to add
- * @v: pointer of type atomic_t
- *
- * Atomically adds @i to @v and returns the result
- */
-#ifndef atomic_add_return
-static inline int atomic_add_return(int i, atomic_t *v)
-{
- unsigned long flags;
- int temp;
-
- raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
- temp = v->counter;
- temp += i;
- v->counter = temp;
- raw_local_irq_restore(flags);
-
- return temp;
-}
-#endif
-
-/**
- * atomic_sub_return - subtract integer from atomic variable
- * @i: integer value to subtract
- * @v: pointer of type atomic_t
- *
- * Atomically subtracts @i from @v and returns the result
- */
-#ifndef atomic_sub_return
-static inline int atomic_sub_return(int i, atomic_t *v)
-{
- unsigned long flags;
- int temp;
-
- raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
- temp = v->counter;
- temp -= i;
- v->counter = temp;
- raw_local_irq_restore(flags);
-
- return temp;
-}
-#endif
-
static inline int atomic_add_negative(int i, atomic_t *v)
{
return atomic_add_return(i, v) < 0;
@@ -139,49 +159,11 @@ static inline void atomic_dec(atomic_t *
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;
-}
-
-/**
- * atomic_clear_mask - Atomically clear bits in atomic variable
- * @mask: Mask of the bits to be cleared
- * @v: pointer of type atomic_t
- *
- * Atomically clears the bits set in @mask from @v
- */
-#ifndef atomic_clear_mask
-static inline void atomic_clear_mask(unsigned long mask, atomic_t *v)
-{
- unsigned long flags;
-
- mask = ~mask;
- raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
- v->counter &= mask;
- raw_local_irq_restore(flags);
-}
-#endif
-
-/**
- * atomic_set_mask - Atomically set bits in atomic variable
- * @mask: Mask of the bits to be set
- * @v: pointer of type atomic_t
- *
- * Atomically sets the bits set in @mask in @v
- */
-#ifndef atomic_set_mask
-static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
-{
- unsigned long flags;
-
- raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
- v->counter |= mask;
- raw_local_irq_restore(flags);
+ int c, old;
+ c = atomic_read(v);
+ while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
+ c = old;
+ return c;
}
-#endif
-#endif /* __KERNEL__ */
#endif /* __ASM_GENERIC_ATOMIC_H */
--- a/include/asm-generic/atomic64.h
+++ b/include/asm-generic/atomic64.h
@@ -20,10 +20,22 @@ typedef struct {
extern long long atomic64_read(const atomic64_t *v);
extern void atomic64_set(atomic64_t *v, long long i);
-extern void atomic64_add(long long a, atomic64_t *v);
-extern long long atomic64_add_return(long long a, atomic64_t *v);
-extern void atomic64_sub(long long a, atomic64_t *v);
-extern long long atomic64_sub_return(long long a, atomic64_t *v);
+
+#define ATOMIC64_OP(op) \
+extern void atomic64_##op(long long a, atomic64_t *v);
+
+#define ATOMIC64_OP_RETURN(op) \
+extern long long atomic64_##op##_return(long long a, atomic64_t *v);
+
+#define ATOMIC64_OPS(op) ATOMIC64_OP(op) ATOMIC_OP_RETURN(op)
+
+ATOMIC64_OPS(add)
+ATOMIC64_OPS(sub)
+
+#undef ATOMIC64_OPS
+#undef ATOMIC64_OP_RETURN
+#undef ATOMIC64_OP
+
extern long long atomic64_dec_if_positive(atomic64_t *v);
extern long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n);
extern long long atomic64_xchg(atomic64_t *v, long long new);
--- a/lib/atomic64.c
+++ b/lib/atomic64.c
@@ -70,53 +70,42 @@ void atomic64_set(atomic64_t *v, long lo
}
EXPORT_SYMBOL(atomic64_set);
-void atomic64_add(long long a, atomic64_t *v)
-{
- unsigned long flags;
- raw_spinlock_t *lock = lock_addr(v);
-
- raw_spin_lock_irqsave(lock, flags);
- v->counter += a;
- raw_spin_unlock_irqrestore(lock, flags);
-}
-EXPORT_SYMBOL(atomic64_add);
-
-long long atomic64_add_return(long long a, atomic64_t *v)
-{
- unsigned long flags;
- raw_spinlock_t *lock = lock_addr(v);
- long long val;
-
- raw_spin_lock_irqsave(lock, flags);
- val = v->counter += a;
- raw_spin_unlock_irqrestore(lock, flags);
- return val;
-}
-EXPORT_SYMBOL(atomic64_add_return);
-
-void atomic64_sub(long long a, atomic64_t *v)
-{
- unsigned long flags;
- raw_spinlock_t *lock = lock_addr(v);
-
- raw_spin_lock_irqsave(lock, flags);
- v->counter -= a;
- raw_spin_unlock_irqrestore(lock, flags);
-}
-EXPORT_SYMBOL(atomic64_sub);
-
-long long atomic64_sub_return(long long a, atomic64_t *v)
-{
- unsigned long flags;
- raw_spinlock_t *lock = lock_addr(v);
- long long val;
-
- raw_spin_lock_irqsave(lock, flags);
- val = v->counter -= a;
- raw_spin_unlock_irqrestore(lock, flags);
- return val;
-}
-EXPORT_SYMBOL(atomic64_sub_return);
+#define ATOMIC64_OP(op, c_op) \
+void atomic64_##op(long long a, atomic64_t *v) \
+{ \
+ unsigned long flags; \
+ raw_spinlock_t *lock = lock_addr(v); \
+ \
+ raw_spin_lock_irqsave(lock, flags); \
+ v->counter c_op a; \
+ raw_spin_unlock_irqrestore(lock, flags); \
+} \
+EXPORT_SYMBOL(atomic64_##op);
+
+#define ATOMIC64_OP_RETURN(op, c_op) \
+long long atomic64_##op##_return(long long a, atomic64_t *v) \
+{ \
+ unsigned long flags; \
+ raw_spinlock_t *lock = lock_addr(v); \
+ long long val; \
+ \
+ raw_spin_lock_irqsave(lock, flags); \
+ val = (v->counter c_op a); \
+ raw_spin_unlock_irqrestore(lock, flags); \
+ return val; \
+} \
+EXPORT_SYMBOL(atomic64_##op##_return);
+
+#define ATOMIC64_OPS(op, c_op) \
+ ATOMIC64_OP(op, c_op) \
+ ATOMIC64_OP_RETURN(op, c_op)
+
+ATOMIC64_OPS(add, +=)
+ATOMIC64_OPS(sub, -=)
+
+#undef ATOMIC64_OPS
+#undef ATOMIC64_OP_RETURN
+#undef ATOMIC64_OP
long long atomic64_dec_if_positive(atomic64_t *v)
{
--
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