* [PATCH 2/2] powerpc: atomic: Implement atomic*_inc_not_zero
2012-03-01 7:09 [PATCH 1/2] atomic: Allow atomic_inc_not_zero to be overridden Anton Blanchard
@ 2012-03-01 7:12 ` Anton Blanchard
2012-03-01 17:19 ` [PATCH 1/2] atomic: Allow atomic_inc_not_zero to be overridden Mike Frysinger
2012-03-01 23:02 ` Andrew Morton
2 siblings, 0 replies; 5+ messages in thread
From: Anton Blanchard @ 2012-03-01 7:12 UTC (permalink / raw)
To: benh, paulus, akpm, asharma, vapier, eric.dumazet
Cc: linuxppc-dev, linux-kernel
Implement atomic_inc_not_zero and atomic64_inc_not_zero. At the
moment we use atomic*_add_unless which requires us to put 0 and
1 constants into registers. We can also avoid a subtract by
saving the original value in a second temporary.
This removes 3 instructions from fget:
- c0000000001b63c0: 39 00 00 00 li r8,0
- c0000000001b63c4: 39 40 00 01 li r10,1
...
- c0000000001b63e8: 7c 0a 00 50 subf r0,r10,r0
Signed-off-by: Anton Blanchard <anton@samba.org>
---
Index: linux-build/arch/powerpc/include/asm/atomic.h
===================================================================
--- linux-build.orig/arch/powerpc/include/asm/atomic.h 2012-02-11 21:42:36.101190317 +1100
+++ linux-build/arch/powerpc/include/asm/atomic.h 2012-02-11 21:58:46.102791345 +1100
@@ -212,6 +212,36 @@ static __inline__ int __atomic_add_unles
return t;
}
+/**
+ * atomic_inc_not_zero - increment unless the number is zero
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1, so long as @v is non-zero.
+ * Returns non-zero if @v was non-zero, and zero otherwise.
+ */
+static __inline__ int atomic_inc_not_zero(atomic_t *v)
+{
+ int t1, t2;
+
+ __asm__ __volatile__ (
+ PPC_ATOMIC_ENTRY_BARRIER
+"1: lwarx %0,0,%2 # atomic_inc_not_zero\n\
+ cmpwi 0,%0,0\n\
+ beq- 2f\n\
+ addic %1,%0,1\n"
+ PPC405_ERR77(0,%2)
+" stwcx. %1,0,%2\n\
+ bne- 1b\n"
+ PPC_ATOMIC_EXIT_BARRIER
+ "\n\
+2:"
+ : "=&r" (t1), "=&r" (t2)
+ : "r" (&v->counter)
+ : "cc", "xer", "memory");
+
+ return t1;
+}
+#define atomic_inc_not_zero(v) atomic_inc_not_zero((v))
#define atomic_sub_and_test(a, v) (atomic_sub_return((a), (v)) == 0)
#define atomic_dec_and_test(v) (atomic_dec_return((v)) == 0)
@@ -467,7 +497,34 @@ static __inline__ int atomic64_add_unles
return t != u;
}
-#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+/**
+ * atomic_inc64_not_zero - increment unless the number is zero
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically increments @v by 1, so long as @v is non-zero.
+ * Returns non-zero if @v was non-zero, and zero otherwise.
+ */
+static __inline__ long atomic64_inc_not_zero(atomic64_t *v)
+{
+ long t1, t2;
+
+ __asm__ __volatile__ (
+ PPC_ATOMIC_ENTRY_BARRIER
+"1: ldarx %0,0,%2 # atomic64_inc_not_zero\n\
+ cmpdi 0,%0,0\n\
+ beq- 2f\n\
+ addic %1,%0,1\n\
+ stdcx. %1,0,%2\n\
+ bne- 1b\n"
+ PPC_ATOMIC_EXIT_BARRIER
+ "\n\
+2:"
+ : "=&r" (t1), "=&r" (t2)
+ : "r" (&v->counter)
+ : "cc", "xer", "memory");
+
+ return t1;
+}
#endif /* __powerpc64__ */
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH 1/2] atomic: Allow atomic_inc_not_zero to be overridden
2012-03-01 7:09 [PATCH 1/2] atomic: Allow atomic_inc_not_zero to be overridden Anton Blanchard
2012-03-01 7:12 ` [PATCH 2/2] powerpc: atomic: Implement atomic*_inc_not_zero Anton Blanchard
2012-03-01 17:19 ` [PATCH 1/2] atomic: Allow atomic_inc_not_zero to be overridden Mike Frysinger
@ 2012-03-01 23:02 ` Andrew Morton
2012-03-01 23:48 ` Richard Kuo
2 siblings, 1 reply; 5+ messages in thread
From: Andrew Morton @ 2012-03-01 23:02 UTC (permalink / raw)
To: Anton Blanchard
Cc: vapier, eric.dumazet, linux-kernel, Richard Kuo, paulus,
linux-hexagon, linuxppc-dev, asharma
On Thu, 1 Mar 2012 18:09:53 +1100
Anton Blanchard <anton@samba.org> wrote:
>
> We want to implement a ppc64 specific version of atomic_inc_not_zero
> so wrap it in an ifdef to allow it to be overridden.
>
> Signed-off-by: Anton Blanchard <anton@samba.org>
> ---
>
> Index: linux-build/include/linux/atomic.h
> ===================================================================
> --- linux-build.orig/include/linux/atomic.h 2012-02-11 14:59:23.284714257 +1100
> +++ linux-build/include/linux/atomic.h 2012-02-11 15:01:14.894764555 +1100
> @@ -24,7 +24,9 @@ static inline int atomic_add_unless(atom
> * Atomically increments @v by 1, so long as @v is non-zero.
> * Returns non-zero if @v was non-zero, and zero otherwise.
> */
> +#ifndef atomic_inc_not_zero
> #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
> +#endif
Please merge this via the ppc tree?
And let's ask the hexagon maintainers to take a look at the definition
in arch/hexagon/include/asm/atomic.h. I assume that it can be removed,
but that might cause problems with files which include asm/atomic.h
directly. I have found two such files in non-arch code and have queued
fixes. There are no such files in arch/hexagon code, so I think it's
safe to zap the hexagon definition of atomic_inc_not_zero().
> +static __inline__ int atomic_inc_not_zero(atomic_t *v)
Curious: is there a technical reason why ppc uses "__inline__" rather
than "inline"?
^ permalink raw reply [flat|nested] 5+ messages in thread