On Oct 7, 2012, at 3:45 PM, Josh Triplett wrote:
> On Sun, Oct 07, 2012 at 07:49:25AM -0500, Ed Cashin wrote:
...
>> CC [M] drivers/block/aoe/demo.o
>> drivers/block/aoe/demo.c:9: warning: `context' attribute directive ignored
>> drivers/block/aoe/demo.c:9: error: expected `,' or `;' before `{' token
>> make[1]: *** [drivers/block/aoe/demo.o] Error 1
>> make: *** [drivers/block/aoe/aoe.ko] Error 2
>
> Oh, that complaint doesn't come from Sparse; that comes from GCC, since
> GCC doesn't understand the context attribute. Look at
> include/linux/compiler.h; it has wrapper macros for the various Sparse
> attributes, and defines them to nothing when not compiling with Sparse.
> If you want to use the context attribute to denote a lock held through a
> function, you need a patch like this:
>
> From 0b862fc1a131a874d157420e9443f16a714596ef Mon Sep 17 00:00:00 2001
> From: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> Date: Sun, 7 Oct 2012 12:41:13 -0700
> Subject: [PATCH] linux/compiler.h: Add __must_hold macro for functions called with a lock held
Ah. OK. So... would you like me to submit your patch to the LKML, or are you doing that?
It seems like a needed addition.
> linux/compiler.h has macros to denote functions that acquire or release
> locks, but not to denote functions called with a lock held that return
> with the lock still held. Add a __must_hold macro to cover this case.
>
> Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> ---
> include/linux/compiler.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index f430e41..b121554 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -10,6 +10,7 @@
> # define __force __attribute__((force))
> # define __nocast __attribute__((nocast))
> # define __iomem __attribute__((noderef, address_space(2)))
> +# define __must_hold(x) __attribute__((context(x,1,1)))
> # define __acquires(x) __attribute__((context(x,0,1)))
> # define __releases(x) __attribute__((context(x,1,0)))
> # define __acquire(x) __context__(x,1)
> @@ -33,6 +34,7 @@ extern void __chk_io_ptr(const volatile void __iomem *);
> # define __chk_user_ptr(x) (void)0
> # define __chk_io_ptr(x) (void)0
> # define __builtin_warning(x, y...) (1)
> +# define __must_hold(x)
> # define __acquires(x)
> # define __releases(x)
> # define __acquire(x) (void)0
--
Ed Cashin
ecashin@xxxxxxxxxx
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