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Groups > linux.kernel > #1438974 > unrolled thread
| Started by | Alexey Dobriyan <adobriyan@gmail.com> |
|---|---|
| First post | 2016-07-08 00:30 +0200 |
| Last post | 2016-07-08 12:30 +0200 |
| Articles | 3 — 2 participants |
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[PATCH] make WRITE_ONCE return void Alexey Dobriyan <adobriyan@gmail.com> - 2016-07-08 00:30 +0200
Re: [PATCH] make WRITE_ONCE return void Peter Zijlstra <peterz@infradead.org> - 2016-07-08 10:10 +0200
Re: [PATCH] make WRITE_ONCE return void Alexey Dobriyan <adobriyan@gmail.com> - 2016-07-08 12:30 +0200
| From | Alexey Dobriyan <adobriyan@gmail.com> |
|---|---|
| Date | 2016-07-08 00:30 +0200 |
| Subject | [PATCH] make WRITE_ONCE return void |
| Message-ID | <rSpXY-4yB-65@gated-at.bofh.it> |
Currently WRITE_ONCE is used as if it returns void. Let's codify this
before somebody tries to be smarter than necessary.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
include/linux/compiler.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -301,7 +301,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
union { typeof(x) __val; char __c[1]; } __u = \
{ .__val = (__force typeof(x)) (val) }; \
__write_once_size(&(x), __u.__c, sizeof(x)); \
- __u.__val; \
+ (void)0; \
})
/**
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| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2016-07-08 10:10 +0200 |
| Message-ID | <rSz1f-26t-7@gated-at.bofh.it> |
| In reply to | #1438974 |
On Fri, Jul 08, 2016 at 01:20:08AM +0300, Alexey Dobriyan wrote:
> Currently WRITE_ONCE is used as if it returns void. Let's codify this
> before somebody tries to be smarter than necessary.
>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
>
> include/linux/compiler.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -301,7 +301,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
> union { typeof(x) __val; char __c[1]; } __u = \
> { .__val = (__force typeof(x)) (val) }; \
> __write_once_size(&(x), __u.__c, sizeof(x)); \
> - __u.__val; \
> + (void)0; \
> })
Why then still use the statement expression? Would it not make more
sense to change it into the regular do { } while (0) form if you want to
remove the return semantics?
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| From | Alexey Dobriyan <adobriyan@gmail.com> |
|---|---|
| Date | 2016-07-08 12:30 +0200 |
| Message-ID | <rSBcK-3ut-7@gated-at.bofh.it> |
| In reply to | #1439166 |
On Fri, Jul 8, 2016 at 11:02 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, Jul 08, 2016 at 01:20:08AM +0300, Alexey Dobriyan wrote:
>> Currently WRITE_ONCE is used as if it returns void. Let's codify this
>> before somebody tries to be smarter than necessary.
>>
>> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
>> ---
>>
>> include/linux/compiler.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --- a/include/linux/compiler.h
>> +++ b/include/linux/compiler.h
>> @@ -301,7 +301,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
>> union { typeof(x) __val; char __c[1]; } __u = \
>> { .__val = (__force typeof(x)) (val) }; \
>> __write_once_size(&(x), __u.__c, sizeof(x)); \
>> - __u.__val; \
>> + (void)0; \
>> })
>
> Why then still use the statement expression? Would it not make more
> sense to change it into the regular do { } while (0) form if you want to
> remove the return semantics?
Statement expression is better because it is an expression
so you can write code like
foo ? WRITE_ONCE(a, 0) : WRITE_ONCE(b, 0)
or
for (... ; ... ; WRITE_ONCE(a, 0), x++)
"do {} while (0)" should be deprecated really.
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