[PATCH -rt 3/5] asm/local.h cmpxchg

Peter Zijlstra
2007-07-14T16:02:29Z

[-- Attachment #1: local.patch --]
[-- Type: text/plain, Size: 4307 bytes --]

From: Christoph Lameter <clameter@sgi.com>

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/asm-generic/local.h | 25 +++++++++++++++++++++++--
include/asm-i386/local.h | 13 +++++++++++++
include/asm-x86_64/local.h | 16 ++++++++++++++++
3 files changed, 52 insertions(+), 2 deletions(-)

Index: linux-2.6.22-rc6-mm1/include/asm-generic/local.h
===================================================================
--- linux-2.6.22-rc6-mm1.orig/include/asm-generic/local.h 2007-07-12 19:44:18.000000000 -0700
+++ linux-2.6.22-rc6-mm1/include/asm-generic/local.h 2007-07-12 19:44:57.000000000 -0700
@@ -46,13 +46,34 @@ typedef struct
#define local_add_unless(l, a, u) atomic_long_add_unless((&(l)->a), (a), (u))
#define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a)

-/* Non-atomic variants, ie. preemption disabled and won't be touched
- * in interrupt, etc. Some archs can optimize this case well. */
+/*
+ * Establish a state necessary for __local_xx functions to work.
+ */
+#define __local_begin(flags) local_irq_disable(flags)
+
+static inline void __local_end(unsigned long flags)
+{
+ local_irq_restore(flags);
+}
+
+/*
+ * Non-atomic variants, ie. within local_begin() / local_end() or
+ * preempt_disable / enable() and won't be touched in interrupt, etc.
+ * Some archs can optimize this case well.
+ */
#define __local_inc(l) local_set((l), local_read(l) + 1)
#define __local_dec(l) local_set((l), local_read(l) - 1)
#define __local_add(i,l) local_set((l), local_read(l) + (i))
#define __local_sub(i,l) local_set((l), local_read(l) - (i))

+#define __local_cmpxchg((v), (o), (n)) (*(v) = (n), (o))
+#define __local_xchg((v), (n)) \
+({ \
+ __typeof(v) x = *(v); \
+ *(v) = (n); \
+ x; \
+)}
+
/* Use these for per-cpu local_t variables: on some archs they are
* much more efficient than these naive implementations. Note they take
* a variable (eg. mystruct.foo), not an address.
Index: linux-2.6.22-rc6-mm1/include/asm-x86_64/local.h
===================================================================
--- linux-2.6.22-rc6-mm1.orig/include/asm-x86_64/local.h 2007-07-12 19:44:18.000000000 -0700
+++ linux-2.6.22-rc6-mm1/include/asm-x86_64/local.h 2007-07-12 19:44:57.000000000 -0700
@@ -9,6 +9,7 @@ typedef struct
atomic_long_t a;
} local_t;

+
#define LOCAL_INIT(i) { ATOMIC_LONG_INIT(i) }

#define local_read(l) atomic_long_read(&(l)->a)
@@ -181,11 +182,26 @@ static __inline__ long local_sub_return(

/* On x86-64 these are better than the atomic variants on SMP kernels
because they dont use a lock prefix. */
+
+#define __local_begin(__flags) \
+{ \
+ (__flags) = 0; \
+ preempt_disable(); \
+}
+
+static inline void __local_end(unsigned long flags) {
+ preempt_enable();
+}
+
#define __local_inc(l) local_inc(l)
#define __local_dec(l) local_dec(l)
#define __local_add(i,l) local_add((i),(l))
#define __local_sub(i,l) local_sub((i),(l))

+#define __local_cmpxchg cmpxchg_local
+#define __local_xchg xchg
+
+
/* Use these for per-cpu local_t variables: on some archs they are
* much more efficient than these naive implementations. Note they take
* a variable, not an address.
Index: linux-2.6.22-rc6-mm1/include/asm-i386/local.h
===================================================================
--- linux-2.6.22-rc6-mm1.orig/include/asm-i386/local.h 2007-07-12 19:53:00.000000000 -0700
+++ linux-2.6.22-rc6-mm1/include/asm-i386/local.h 2007-07-12 19:55:22.000000000 -0700
@@ -194,12 +194,25 @@ static __inline__ long local_sub_return(
})
#define local_inc_not_zero(l) local_add_unless((l), 1, 0)

+#define __local_begin(__flags) \
+{ \
+ (__flags) = 0; \
+ preempt_disable(); \
+}
+
+static inline void __local_end(unsigned long flags) {
+ preempt_enable();
+}
+
/* On x86, these are no better than the atomic variants. */
#define __local_inc(l) local_inc(l)
#define __local_dec(l) local_dec(l)
#define __local_add(i,l) local_add((i),(l))
#define __local_sub(i,l) local_sub((i),(l))

+#define __local_cmpxchg cmpxchg_local
+#define __local_xchg xchg
+
/* Use these for per-cpu local_t variables: on some archs they are
* much more efficient than these naive implementations. Note they take
* a variable, not an address.

--