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Subject[PATCHv2 16/16] atomics/treewide: make conditional inc/dec ops optional
Date
The conditional inc/dec ops differ for atomic_t and atomic64_t:

* atomic_inc_unless_positive() is optional for atomic_t, and doesn't exist for
atomic64_t.

* atomic_dec_unless_negative() is optional for atomic_t, and doesn't exist for
atomic64_t.

* atomic_dec_if_positive is optional for atomic_t, and is mandatory for
atomic64_t.

Let's make these consistently optional for both. At the same time, let's clean
up the exisiting fallbacks to use atomic_try_cmpxchg().

The instrumented atomics are updated accordingly.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
---
arch/alpha/include/asm/atomic.h | 1 +
arch/arc/include/asm/atomic.h | 1 +
arch/arm/include/asm/atomic.h | 1 +
arch/arm64/include/asm/atomic.h | 2 +
arch/ia64/include/asm/atomic.h | 16 -----
arch/parisc/include/asm/atomic.h | 23 --------
arch/powerpc/include/asm/atomic.h | 1 +
arch/s390/include/asm/atomic.h | 17 ------
arch/sparc/include/asm/atomic_64.h | 1 +
arch/x86/include/asm/atomic64_32.h | 1 +
arch/x86/include/asm/atomic64_64.h | 18 ------
include/asm-generic/atomic-instrumented.h | 3 +
include/asm-generic/atomic64.h | 1 +
include/linux/atomic.h | 97 +++++++++++++++++++++++--------
14 files changed, 85 insertions(+), 98 deletions(-)

diff --git a/arch/alpha/include/asm/atomic.h b/arch/alpha/include/asm/atomic.h
index 9c50cc512a78..81bf9d15dcc1 100644
--- a/arch/alpha/include/asm/atomic.h
+++ b/arch/alpha/include/asm/atomic.h
@@ -296,5 +296,6 @@ static inline long atomic64_dec_if_positive(atomic64_t *v)
smp_mb();
return old - 1;
}
+#define atomic64_dec_if_positive atomic64_dec_if_positive

#endif /* _ALPHA_ATOMIC_H */
diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index abffdc525b46..261c6a4d3f05 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -517,6 +517,7 @@ static inline long long atomic64_dec_if_positive(atomic64_t *v)

return val;
}
+#define atomic64_dec_if_positive atomic64_dec_if_positive

/**
* atomic64_fetch_add_unless - add unless the number is a given value
diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
index 5a58d061d3d2..884c241424fe 100644
--- a/arch/arm/include/asm/atomic.h
+++ b/arch/arm/include/asm/atomic.h
@@ -474,6 +474,7 @@ static inline long long atomic64_dec_if_positive(atomic64_t *v)

return result;
}
+#define atomic64_dec_if_positive atomic64_dec_if_positive

static inline long long atomic64_fetch_add_unless(atomic64_t *v, long long a,
long long u)
diff --git a/arch/arm64/include/asm/atomic.h b/arch/arm64/include/asm/atomic.h
index 078f785cd97f..9bca54dda75c 100644
--- a/arch/arm64/include/asm/atomic.h
+++ b/arch/arm64/include/asm/atomic.h
@@ -159,5 +159,7 @@

#define atomic64_andnot atomic64_andnot

+#define atomic64_dec_if_positive atomic64_dec_if_positive
+
#endif
#endif
diff --git a/arch/ia64/include/asm/atomic.h b/arch/ia64/include/asm/atomic.h
index 46a15a974bed..206530d0751b 100644
--- a/arch/ia64/include/asm/atomic.h
+++ b/arch/ia64/include/asm/atomic.h
@@ -215,22 +215,6 @@ ATOMIC64_FETCH_OP(xor, ^)
(cmpxchg(&((v)->counter), old, new))
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))

-static __inline__ long atomic64_dec_if_positive(atomic64_t *v)
-{
- long c, old, dec;
- c = atomic64_read(v);
- for (;;) {
- dec = c - 1;
- if (unlikely(dec < 0))
- break;
- old = atomic64_cmpxchg((v), c, dec);
- if (likely(old == c))
- break;
- c = old;
- }
- return dec;
-}
-
#define atomic_add(i,v) (void)atomic_add_return((i), (v))
#define atomic_sub(i,v) (void)atomic_sub_return((i), (v))

diff --git a/arch/parisc/include/asm/atomic.h b/arch/parisc/include/asm/atomic.h
index 10bc490327c1..118953d41763 100644
--- a/arch/parisc/include/asm/atomic.h
+++ b/arch/parisc/include/asm/atomic.h
@@ -223,29 +223,6 @@ atomic64_read(const atomic64_t *v)
((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))

-/*
- * atomic64_dec_if_positive - decrement by 1 if old value positive
- * @v: pointer of type atomic_t
- *
- * The function returns the old value of *v minus 1, even if
- * the atomic variable, v, was not decremented.
- */
-static inline long atomic64_dec_if_positive(atomic64_t *v)
-{
- long c, old, dec;
- c = atomic64_read(v);
- for (;;) {
- dec = c - 1;
- if (unlikely(dec < 0))
- break;
- old = atomic64_cmpxchg((v), c, dec);
- if (likely(old == c))
- break;
- c = old;
- }
- return dec;
-}
-
#endif /* !CONFIG_64BIT */


diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h
index ebaefdee4a57..a0156cb43d1f 100644
--- a/arch/powerpc/include/asm/atomic.h
+++ b/arch/powerpc/include/asm/atomic.h
@@ -488,6 +488,7 @@ static __inline__ long atomic64_dec_if_positive(atomic64_t *v)

return t;
}
+#define atomic64_dec_if_positive atomic64_dec_if_positive

#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
#define atomic64_cmpxchg_relaxed(v, o, n) \
diff --git a/arch/s390/include/asm/atomic.h b/arch/s390/include/asm/atomic.h
index 376e64af951f..fd20ab5d4cf7 100644
--- a/arch/s390/include/asm/atomic.h
+++ b/arch/s390/include/asm/atomic.h
@@ -145,23 +145,6 @@ ATOMIC64_OPS(xor)

#undef ATOMIC64_OPS

-static inline long atomic64_dec_if_positive(atomic64_t *v)
-{
- long c, old, dec;
-
- c = atomic64_read(v);
- for (;;) {
- dec = c - 1;
- if (unlikely(dec < 0))
- break;
- old = atomic64_cmpxchg((v), c, dec);
- if (likely(old == c))
- break;
- c = old;
- }
- return dec;
-}
-
#define atomic64_sub_return(_i, _v) atomic64_add_return(-(long)(_i), _v)
#define atomic64_fetch_sub(_i, _v) atomic64_fetch_add(-(long)(_i), _v)
#define atomic64_sub(_i, _v) atomic64_add(-(long)(_i), _v)
diff --git a/arch/sparc/include/asm/atomic_64.h b/arch/sparc/include/asm/atomic_64.h
index 304865c7cdbb..6963482c81d8 100644
--- a/arch/sparc/include/asm/atomic_64.h
+++ b/arch/sparc/include/asm/atomic_64.h
@@ -62,5 +62,6 @@ static inline int atomic_xchg(atomic_t *v, int new)
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))

long atomic64_dec_if_positive(atomic64_t *v);
+#define atomic64_dec_if_positive atomic64_dec_if_positive

#endif /* !(__ARCH_SPARC64_ATOMIC__) */
diff --git a/arch/x86/include/asm/atomic64_32.h b/arch/x86/include/asm/atomic64_32.h
index 472c7af0ed48..ef959f02d070 100644
--- a/arch/x86/include/asm/atomic64_32.h
+++ b/arch/x86/include/asm/atomic64_32.h
@@ -254,6 +254,7 @@ static inline int arch_atomic64_inc_not_zero(atomic64_t *v)
return r;
}

+#define arch_atomic64_dec_if_positive arch_atomic64_dec_if_positive
static inline long long arch_atomic64_dec_if_positive(atomic64_t *v)
{
long long r;
diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
index 1b282272a801..849f1c566a11 100644
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -191,24 +191,6 @@ static inline long arch_atomic64_xchg(atomic64_t *v, long new)
return xchg(&v->counter, new);
}

-/*
- * arch_atomic64_dec_if_positive - decrement by 1 if old value positive
- * @v: pointer of type atomic_t
- *
- * The function returns the old value of *v minus 1, even if
- * the atomic variable, v, was not decremented.
- */
-static inline long arch_atomic64_dec_if_positive(atomic64_t *v)
-{
- s64 dec, c = arch_atomic64_read(v);
- do {
- dec = c - 1;
- if (unlikely(dec < 0))
- break;
- } while (!arch_atomic64_try_cmpxchg(v, &c, dec));
- return dec;
-}
-
static inline void arch_atomic64_and(long i, atomic64_t *v)
{
asm volatile(LOCK_PREFIX "andq %1,%0"
diff --git a/include/asm-generic/atomic-instrumented.h b/include/asm-generic/atomic-instrumented.h
index 8c9887a0cb1d..1458de7ece87 100644
--- a/include/asm-generic/atomic-instrumented.h
+++ b/include/asm-generic/atomic-instrumented.h
@@ -243,11 +243,14 @@ static __always_inline s64 atomic64_inc_not_zero(atomic64_t *v)
}
#endif

+#ifdef arch_atomic64_dec_if_positive
+#define atomic64_dec_if_positive atomic64_dec_if_positive
static __always_inline s64 atomic64_dec_if_positive(atomic64_t *v)
{
kasan_check_write(v, sizeof(*v));
return arch_atomic64_dec_if_positive(v);
}
+#endif

#ifdef arch_atomic_dec_and_test
#define atomic_dec_and_test atomic_dec_and_test
diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
index 1810a0ca96ec..296f1b3c6661 100644
--- a/include/asm-generic/atomic64.h
+++ b/include/asm-generic/atomic64.h
@@ -50,6 +50,7 @@ ATOMIC64_OPS(xor)
#undef ATOMIC64_OP

extern long long atomic64_dec_if_positive(atomic64_t *v);
+#define atomic64_dec_if_positive atomic64_dec_if_positive
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);
extern long long atomic64_fetch_add_unless(atomic64_t *v, long long a, long long u);
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index d6ec2dc37057..9c1b0769a846 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -681,28 +681,30 @@ static inline int atomic_fetch_andnot_release(int i, atomic_t *v)
#endif

#ifndef atomic_inc_unless_negative
-static inline int atomic_inc_unless_negative(atomic_t *p)
+static inline bool atomic_inc_unless_negative(atomic_t *v)
{
- int v, v1;
- for (v = 0; v >= 0; v = v1) {
- v1 = atomic_cmpxchg(p, v, v + 1);
- if (likely(v1 == v))
- return 1;
- }
- return 0;
+ int c = atomic_read(v);
+
+ do {
+ if (unlikely(c < 0))
+ return false;
+ } while (!atomic_try_cmpxchg(v, &c, c + 1));
+
+ return true;
}
#endif

#ifndef atomic_dec_unless_positive
-static inline int atomic_dec_unless_positive(atomic_t *p)
+static inline bool atomic_dec_unless_positive(atomic_t *v)
{
- int v, v1;
- for (v = 0; v <= 0; v = v1) {
- v1 = atomic_cmpxchg(p, v, v - 1);
- if (likely(v1 == v))
- return 1;
- }
- return 0;
+ int c = atomic_read(v);
+
+ do {
+ if (unlikely(c > 0))
+ return false;
+ } while (!atomic_try_cmpxchg(v, &c, c - 1));
+
+ return true;
}
#endif

@@ -716,17 +718,14 @@ static inline int atomic_dec_unless_positive(atomic_t *p)
#ifndef atomic_dec_if_positive
static inline int atomic_dec_if_positive(atomic_t *v)
{
- int c, old, dec;
- c = atomic_read(v);
- for (;;) {
+ int dec, c = atomic_read(v);
+
+ do {
dec = c - 1;
if (unlikely(dec < 0))
break;
- old = atomic_cmpxchg((v), c, dec);
- if (likely(old == c))
- break;
- c = old;
- }
+ } while (!atomic_try_cmpxchg(v, &c, dec));
+
return dec;
}
#endif
@@ -1287,6 +1286,56 @@ static inline long long atomic64_fetch_andnot_release(long long i, atomic64_t *v
}
#endif

+#ifndef atomic64_inc_unless_negative
+static inline bool atomic64_inc_unless_negative(atomic64_t *v)
+{
+ long long c = atomic64_read(v);
+
+ do {
+ if (unlikely(c < 0))
+ return false;
+ } while (!atomic64_try_cmpxchg(v, &c, c + 1));
+
+ return true;
+}
+#endif
+
+#ifndef atomic64_dec_unless_positive
+static inline bool atomic64_dec_unless_positive(atomic64_t *v)
+{
+ long long c = atomic64_read(v);
+
+ do {
+ if (unlikely(c > 0))
+ return false;
+ } while (!atomic64_try_cmpxchg(v, &c, c - 1));
+
+ return true;
+}
+#endif
+
+/*
+ * atomic64_dec_if_positive - decrement by 1 if old value positive
+ * @v: pointer of type atomic64_t
+ *
+ * The function returns the old value of *v minus 1, even if
+ * the atomic64 variable, v, was not decremented.
+ */
+#ifndef atomic64_dec_if_positive
+static inline long long atomic64_dec_if_positive(atomic64_t *v)
+{
+ long long dec, c = atomic64_read(v);
+
+ do {
+ dec = c - 1;
+ if (unlikely(dec < 0))
+ break;
+ } while (!atomic64_try_cmpxchg(v, &c, dec));
+
+ return dec;
+}
+#endif
+
#define atomic64_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c))

#include <asm-generic/atomic-long.h>
--
2.11.0
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