[PATCH] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[PATCH] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[Zhang Yanfei]

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@intel.com>
Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
---
 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;
 EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss);
 
 static inline void cpu_crash_vmclear_loaded_vmcss(void)
@@ -46,7 +46,7 @@ static inline void cpu_crash_vmclear_loaded_vmcss(void)
 	void (*do_vmclear_operation)(void) = NULL;
 
 	rcu_read_lock();
-	do_vmclear_operation = rcu_dereference(crash_vmclear_loaded_vmcss);
+	do_vmclear_operation = vmclear_func_rcu(crash_vmclear_loaded_vmcss);
 	if (do_vmclear_operation)
 		do_vmclear_operation();
 	rcu_read_unlock();
-- 
1.7.1

Re: [PATCH] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[Marcelo Tosatti]

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@intel.com>
> Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
> ---
>  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.

Re: [PATCH] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[Zhang Yanfei]

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@intel.com>
>> Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
>> ---
>>  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

Re: [PATCH] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[Gleb Natapov]

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@intel.com>
> >> Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
> >> ---
> >>  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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Re: [PATCH] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[Zhang Yanfei]

于 2012年12月11日 16:10, Gleb Natapov 写道:
> 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@intel.com>
>>>> Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
>>>> ---
>>>>  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.
> 

Thanks. typedef works.

[PATCH] [RESEND] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[Zhang Yanfei]

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@intel.com>
Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
---
 arch/x86/include/asm/kexec.h |    3 ++-
 arch/x86/kernel/crash.c      |    4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index 28feeba..6080d26 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -163,7 +163,8 @@ struct kimage_arch {
 };
 #endif
 
-extern void (*crash_vmclear_loaded_vmcss)(void);
+typedef void crash_vmclear_fn(void);
+extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 2f6b8e8..74467fe 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -38,12 +38,12 @@ int in_crash_kexec;
  *
  * protected by rcu.
  */
-void (*crash_vmclear_loaded_vmcss)(void) = NULL;
+crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss = NULL;
 EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss);
 
 static inline void cpu_crash_vmclear_loaded_vmcss(void)
 {
-	void (*do_vmclear_operation)(void) = NULL;
+	crash_vmclear_fn *do_vmclear_operation = NULL;
 
 	rcu_read_lock();
 	do_vmclear_operation = rcu_dereference(crash_vmclear_loaded_vmcss);
-- 
1.7.1

Re: [PATCH] [RESEND] x86/kexec: crash_vmclear_local_vmcss needs __rcu

[Marcelo Tosatti]

On Tue, Dec 11, 2012 at 05:11:34PM +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-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Zhang Yanfei <zhangyanfei-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  arch/x86/include/asm/kexec.h |    3 ++-
>  arch/x86/kernel/crash.c      |    4 ++--
>  2 files changed, 4 insertions(+), 3 deletions(-)

Applied, thanks.