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.
Thanks
Zhang Yanfei
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