Re: percpu: Implement this_cpu_add,sub,dec,inc_return

[Christoph Lameter <cl@linux.com>]

On Fri, 19 Nov 2010, Eric Dumazet wrote:

> > This isnt a use case for this_cpu_dec right? Seems that your message was
> > cut off?
> I wanted to show you the file were it was possible to use this_cpu_{dec|
> inc}_return()
>
> My patch on kmap_atomic_idx() doesnt need your new functions ;)

Oh ok you mean this:

---
 include/linux/highmem.h |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Index: linux-2.6/include/linux/highmem.h
===================================================================
--- linux-2.6.orig/include/linux/highmem.h	2010-11-19 09:55:24.000000000 -0600
+++ linux-2.6/include/linux/highmem.h	2010-11-19 09:57:54.000000000 -0600
@@ -81,7 +81,9 @@ DECLARE_PER_CPU(int, __kmap_atomic_idx);

 static inline int kmap_atomic_idx_push(void)
 {
-	int idx = __get_cpu_var(__kmap_atomic_idx)++;
+	int idx = __this_cpu_read(__kmap_atomic_idx);
+
+	__this_cpu_inc(__kmap_atomic_idx);
 #ifdef CONFIG_DEBUG_HIGHMEM
 	WARN_ON_ONCE(in_irq() && !irqs_disabled());
 	BUG_ON(idx > KM_TYPE_NR);
@@ -91,12 +93,12 @@ static inline int kmap_atomic_idx_push(v

 static inline int kmap_atomic_idx(void)
 {
-	return __get_cpu_var(__kmap_atomic_idx) - 1;
+	return __this_cpu_read(__kmap_atomic_idx) - 1;
 }

 static inline int kmap_atomic_idx_pop(void)
 {
-	int idx = --__get_cpu_var(__kmap_atomic_idx);
+	int idx = __this_cpu_dec_return(__kmap_atomic_idx);
 #ifdef CONFIG_DEBUG_HIGHMEM
 	BUG_ON(idx < 0);
 #endif

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