2021-04-06 15:47:33

by Gao Xiang

[permalink] [raw]
Subject: [PATCH] parisc: avoid a warning on u8 cast for cmpxchg on u8 pointers

From: Gao Xiang <[email protected]>

commit b344d6a83d01 ("parisc: add support for cmpxchg on u8 pointers")
can generate a sparse warningi ("cast truncates bits from constant
value"), which has been reported several times [1] [2] [3].

The original code worked as expected, but anyway, let silence such
sparse warning as what others did [4].

[1] https://lore.kernel.org/r/[email protected]
[2] https://lore.kernel.org/r/[email protected]
[3] https://lore.kernel.org/r/202008210829.KVwn7Xeh%[email protected]
[4] https://lore.kernel.org/r/[email protected]
Cc: Liam Beguin <[email protected]>
Cc: Helge Deller <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
---
arch/parisc/include/asm/cmpxchg.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/parisc/include/asm/cmpxchg.h b/arch/parisc/include/asm/cmpxchg.h
index cf5ee9b0b393..84ee232278a6 100644
--- a/arch/parisc/include/asm/cmpxchg.h
+++ b/arch/parisc/include/asm/cmpxchg.h
@@ -72,7 +72,7 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size)
#endif
case 4: return __cmpxchg_u32((unsigned int *)ptr,
(unsigned int)old, (unsigned int)new_);
- case 1: return __cmpxchg_u8((u8 *)ptr, (u8)old, (u8)new_);
+ case 1: return __cmpxchg_u8((u8 *)ptr, old & 0xff, new_ & 0xff);
}
__cmpxchg_called_with_bad_pointer();
return old;
--
2.20.1


2021-04-06 17:47:52

by Rolf Eike Beer

[permalink] [raw]
Subject: Re: [PATCH] parisc: avoid a warning on u8 cast for cmpxchg on u8 pointers

Am Dienstag, 6. April 2021, 06:59:29 CEST schrieb Gao Xiang:
> From: Gao Xiang <[email protected]>
>
> commit b344d6a83d01 ("parisc: add support for cmpxchg on u8 pointers")
> can generate a sparse warningi ("cast truncates bits from constant
^
> value"), which has been reported several times [1] [2] [3].

Attachments:
signature.asc (201.00 B)
This is a digitally signed message part.

2021-04-06 18:58:04

by Helge Deller

[permalink] [raw]
Subject: Re: [PATCH] parisc: avoid a warning on u8 cast for cmpxchg on u8 pointers

On 4/6/21 6:59 AM, Gao Xiang wrote:
> From: Gao Xiang <[email protected]>
>
> commit b344d6a83d01 ("parisc: add support for cmpxchg on u8 pointers")
> can generate a sparse warningi ("cast truncates bits from constant
> value"), which has been reported several times [1] [2] [3].
>
> The original code worked as expected, but anyway, let silence such
> sparse warning as what others did [4].
>
> [1] https://lore.kernel.org/r/[email protected]
> [2] https://lore.kernel.org/r/[email protected]
> [3] https://lore.kernel.org/r/202008210829.KVwn7Xeh%[email protected]
> [4] https://lore.kernel.org/r/[email protected]
> Cc: Liam Beguin <[email protected]>
> Cc: Helge Deller <[email protected]>
> Signed-off-by: Gao Xiang <[email protected]>

applied to the parisc for-next git tree.
(I fixed up the typo above too)

Thanks!
Helge

> ---
> arch/parisc/include/asm/cmpxchg.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/parisc/include/asm/cmpxchg.h b/arch/parisc/include/asm/cmpxchg.h
> index cf5ee9b0b393..84ee232278a6 100644
> --- a/arch/parisc/include/asm/cmpxchg.h
> +++ b/arch/parisc/include/asm/cmpxchg.h
> @@ -72,7 +72,7 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size)
> #endif
> case 4: return __cmpxchg_u32((unsigned int *)ptr,
> (unsigned int)old, (unsigned int)new_);
> - case 1: return __cmpxchg_u8((u8 *)ptr, (u8)old, (u8)new_);
> + case 1: return __cmpxchg_u8((u8 *)ptr, old & 0xff, new_ & 0xff);
> }
> __cmpxchg_called_with_bad_pointer();
> return old;
>

2021-04-06 20:16:23

by Gao Xiang

[permalink] [raw]
Subject: Re: [PATCH] parisc: avoid a warning on u8 cast for cmpxchg on u8 pointers

On Tue, Apr 06, 2021 at 12:08:55PM +0200, Helge Deller wrote:
> On 4/6/21 6:59 AM, Gao Xiang wrote:
> > From: Gao Xiang <[email protected]>
> >
> > commit b344d6a83d01 ("parisc: add support for cmpxchg on u8 pointers")
> > can generate a sparse warningi ("cast truncates bits from constant
> > value"), which has been reported several times [1] [2] [3].
> >
> > The original code worked as expected, but anyway, let silence such
> > sparse warning as what others did [4].
> >
> > [1] https://lore.kernel.org/r/[email protected]
> > [2] https://lore.kernel.org/r/[email protected]
> > [3] https://lore.kernel.org/r/202008210829.KVwn7Xeh%[email protected]
> > [4] https://lore.kernel.org/r/[email protected]
> > Cc: Liam Beguin <[email protected]>
> > Cc: Helge Deller <[email protected]>
> > Signed-off-by: Gao Xiang <[email protected]>
>
> applied to the parisc for-next git tree.
> (I fixed up the typo above too)

Thanks all! :)

Thanks,
Gao Xiang

>
> Thanks!
> Helge
>
> > ---
> > arch/parisc/include/asm/cmpxchg.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/parisc/include/asm/cmpxchg.h b/arch/parisc/include/asm/cmpxchg.h
> > index cf5ee9b0b393..84ee232278a6 100644
> > --- a/arch/parisc/include/asm/cmpxchg.h
> > +++ b/arch/parisc/include/asm/cmpxchg.h
> > @@ -72,7 +72,7 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new_, int size)
> > #endif
> > case 4: return __cmpxchg_u32((unsigned int *)ptr,
> > (unsigned int)old, (unsigned int)new_);
> > - case 1: return __cmpxchg_u8((u8 *)ptr, (u8)old, (u8)new_);
> > + case 1: return __cmpxchg_u8((u8 *)ptr, old & 0xff, new_ & 0xff);
> > }
> > __cmpxchg_called_with_bad_pointer();
> > return old;
> >
>