Re: [PATCH] compiler, READ_ONCE: Fix build failure with some older GCC

2015-10-15 Thread Ingo Molnar

* Andrey Ryabinin  wrote:

> Some old versions of GCC doesn't handle __alias (or maybe a combination
> of 'static __always_inline __alias') right.
> 
> GCC creates outline and unused copy of __read_once_size_check()
> function in the object file which references memcpy and causes
> the build failure:
>   arch/x86/entry/vdso/vclock_gettime.o: In function 
> `__read_once_size_check':
>   vclock_gettime.c:(.text+0x5f): undefined reference to `memcpy'
>   arch/x86/entry/vdso/vgetcpu.o: In function `__read_once_size_check':
>   vgetcpu.c:(.text+0x2f): undefined reference to `memcpy'
> 
> We could avoid using alias to work around this problem.
> 
> Reported-by: Stephen Rothwell 
> Signed-off-by: Andrey Ryabinin 
> ---
>  include/linux/compiler.h | 7 +--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index aa2ae4c..3436a4c 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -231,8 +231,11 @@ void __read_once_size_nocheck(const volatile void *p, 
> void *res, int size)
>   __READ_ONCE_SIZE;
>  }
>  #else
> -static __always_inline __alias(__read_once_size_check)
> -void __read_once_size_nocheck(const volatile void *p, void *res, int size);
> +static __always_inline
> +void __read_once_size_nocheck(const volatile void *p, void *res, int size)
> +{
> + __READ_ONCE_SIZE;
> +}
>  #endif

Yeah, so could you please re-send the original two patches, with all the 
changes 
(typo fixes, renaming, this build fix, etc.) propagated that were found in 
testing 
and that were suggested in the review thread?

I'll remove the broken commits from linux-next meanwhile.

Thanks,

Ingo
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[PATCH] compiler, READ_ONCE: Fix build failure with some older GCC

2015-10-15 Thread Andrey Ryabinin
Some old versions of GCC doesn't handle __alias (or maybe a combination
of 'static __always_inline __alias') right.

GCC creates outline and unused copy of __read_once_size_check()
function in the object file which references memcpy and causes
the build failure:
arch/x86/entry/vdso/vclock_gettime.o: In function 
`__read_once_size_check':
vclock_gettime.c:(.text+0x5f): undefined reference to `memcpy'
arch/x86/entry/vdso/vgetcpu.o: In function `__read_once_size_check':
vgetcpu.c:(.text+0x2f): undefined reference to `memcpy'

We could avoid using alias to work around this problem.

Reported-by: Stephen Rothwell 
Signed-off-by: Andrey Ryabinin 
---
 include/linux/compiler.h | 7 +--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index aa2ae4c..3436a4c 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -231,8 +231,11 @@ void __read_once_size_nocheck(const volatile void *p, void 
*res, int size)
__READ_ONCE_SIZE;
 }
 #else
-static __always_inline __alias(__read_once_size_check)
-void __read_once_size_nocheck(const volatile void *p, void *res, int size);
+static __always_inline
+void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+{
+   __READ_ONCE_SIZE;
+}
 #endif
 
 static __always_inline void __write_once_size(volatile void *p, void *res, int 
size)
-- 
2.4.9

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