2010-02-26 11:22:57

by Luca Barbieri

Subject: [PATCH 1/2] lib: only test atomic64_dec_if_positive on archs having it

Only supported by ppc, mips and x86-32 with my patchset.

Signed-off-by: Luca Barbieri <[email protected]>
---
lib/atomic64_test.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/lib/atomic64_test.c b/lib/atomic64_test.c
index 4ff649e..0effcac 100644
--- a/lib/atomic64_test.c
+++ b/lib/atomic64_test.c
@@ -112,6 +112,7 @@ static __init int test_atomic64(void)
r += one;
BUG_ON(v.counter != r);

+#if defined(CONFIG_X86_32) || defined(CONFIG_MIPS) || defined(CONFIG_PPC) || defined(_ASM_GENERIC_ATOMIC64_H)
INIT(onestwos);
BUG_ON(atomic64_dec_if_positive(&v) != (onestwos - 1));
r -= one;
@@ -124,6 +125,9 @@ static __init int test_atomic64(void)
INIT(-one);
BUG_ON(atomic64_dec_if_positive(&v) != (-one - one));
BUG_ON(v.counter != r);
+#else
+#warning Please implement atomic64_dec_if_positive for your architecture, and add it to the IF above
+#endif

INIT(onestwos);
BUG_ON(atomic64_inc_not_zero(&v));
--
1.6.6.1.476.g01ddb

2010-02-26 11:23:01

by Luca Barbieri

Subject: [PATCH 2/2] x86: implement atomic[64]_dec_if_positive

They were missing.

atomic64_dec_if_positive for x86-32 is implemented in my atomic64
improvements for x86-32 patchset.

Signed-off-by: Luca Barbieri <[email protected]>
---
arch/x86/include/asm/atomic.h | 23 +++++++++++++++++++++++
arch/x86/include/asm/atomic64_64.h | 23 +++++++++++++++++++++++
lib/atomic64_test.c | 2 +-
3 files changed, 47 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index 8f8217b..706c694 100644
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -246,6 +246,29 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u)

#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)

+/*
+ * atomic_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 int atomic_dec_if_positive(atomic_t *v)
+{
+ int c, old, dec;
+ c = atomic_read(v);
+ for (;;) {
+ dec = c - 1;
+ if (unlikely(dec < 0))
+ break;
+ old = atomic_cmpxchg((v), c, dec);
+ if (likely(old == c))
+ break;
+ c = old;
+ }
+ return dec;
+}
+
/**
* atomic_inc_short - increment of a short integer
* @v: pointer to type int
diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
index 51c5b40..4d6e2cd 100644
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -221,4 +221,27 @@ static inline int atomic64_add_unless(atomic64_t *v, long a, long u)

#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)

+/*
+ * 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 /* _ASM_X86_ATOMIC64_64_H */
diff --git a/lib/atomic64_test.c b/lib/atomic64_test.c
index 0effcac..58efdab 100644
--- a/lib/atomic64_test.c
+++ b/lib/atomic64_test.c
@@ -112,7 +112,7 @@ static __init int test_atomic64(void)
r += one;
BUG_ON(v.counter != r);

-#if defined(CONFIG_X86_32) || defined(CONFIG_MIPS) || defined(CONFIG_PPC) || defined(_ASM_GENERIC_ATOMIC64_H)
+#if defined(CONFIG_X86) || defined(CONFIG_MIPS) || defined(CONFIG_PPC) || defined(_ASM_GENERIC_ATOMIC64_H)
INIT(onestwos);
BUG_ON(atomic64_dec_if_positive(&v) != (onestwos - 1));
r -= one;
--
1.6.6.1.476.g01ddb