On Tue, Dec 11, 2012 at 04:04:55PM +0800, Zhang Yanfei wrote:
> 于 2012年12月11日 04:30, Marcelo Tosatti 写道:
> > On Fri, Dec 07, 2012 at 01:40:56PM +0800, Zhang Yanfei wrote:
> >> This removes the sparse warning:
> >> arch/x86/kernel/crash.c:49:32: sparse: incompatible types in comparison expression (different address spaces)
> >>
> >> Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
> >> Signed-off-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
> >> ---
> >> arch/x86/include/asm/kexec.h | 4 +++-
> >> arch/x86/kernel/crash.c | 4 ++--
> >> 2 files changed, 5 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> >> index 28feeba..16882cd 100644
> >> --- a/arch/x86/include/asm/kexec.h
> >> +++ b/arch/x86/include/asm/kexec.h
> >> @@ -163,7 +163,9 @@ struct kimage_arch {
> >> };
> >> #endif
> >>
> >> -extern void (*crash_vmclear_loaded_vmcss)(void);
> >> +extern void __rcu (*crash_vmclear_loaded_vmcss)(void);
> >> +#define vmclear_func_rcu(vmclear_func) \
> >> + ((void (*)(void)) rcu_dereference(vmclear_func))
> >>
> >> #endif /* __ASSEMBLY__ */
> >>
> >> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> >> index 2f6b8e8..50ce1d6 100644
> >> --- a/arch/x86/kernel/crash.c
> >> +++ b/arch/x86/kernel/crash.c
> >> @@ -38,7 +38,7 @@ int in_crash_kexec;
> >> *
> >> * protected by rcu.
> >> */
> >> -void (*crash_vmclear_loaded_vmcss)(void) = NULL;
> >> +void __rcu (*crash_vmclear_loaded_vmcss)(void) = NULL;
> >
> > Isnt this (__rcu AS tag) sufficient? After all, sparse is complaining
> > about namespaces.
> >
> > Creating a #define to cast seems excessive.
> >
> >
>
> I am not very familiar with the rcu.
> Adding __rcu tag could solve the problem. But it imported another warning
> when I try to assign rcu_dereference(crash_vmclear_loaded_vmcss) to
> do_vmclear_operation:
>
> arch/x86/kernel/crash.c:49:30: warning: incorrect type in assignment (different modifiers)
> arch/x86/kernel/crash.c:49:30: expected void ( *do_vmclear_operation )( ... )
> arch/x86/kernel/crash.c:49:30: got void ( [noderef] *<noident> )( ... )
> arch/x86/kernel/crash.c:49:30: warning: incorrect type in assignment (different modifiers)
> arch/x86/kernel/crash.c:49:30: expected void ( *do_vmclear_operation )( ... )
> arch/x86/kernel/crash.c:49:30: got void ( [noderef] *<noident> )( ... )
>
> So I made the #define to cast its type.
>
> If you have any suggestion, that'll be helpful.
>
Try to use typedef.
--
Gleb.
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