From: Ran Xiaokai <[email protected]>
huge_anon_orders_always and huge_anon_orders_always are accessed
lockless, it is better to use the READ_ONCE() wrapper.
This is not fixing any visible bug, hopefully this can cease some
KCSAN complains in the future.
Also do that for huge_anon_orders_madvise.
Signed-off-by: Ran Xiaokai <[email protected]>
---
include/linux/huge_mm.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index de0c89105076..6573430ea600 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -122,8 +122,8 @@ static inline bool hugepage_flags_enabled(void)
* So we don't need to look at huge_anon_orders_inherit.
*/
return hugepage_global_enabled() ||
- huge_anon_orders_always ||
- huge_anon_orders_madvise;
+ READ_ONCE(huge_anon_orders_always) ||
+ READ_ONCE(huge_anon_orders_madvise);
}
static inline int highest_order(unsigned long orders)
--
2.15.2
On 11.05.24 08:44, [email protected] wrote:
> From: Ran Xiaokai <[email protected]>
>
> huge_anon_orders_always and huge_anon_orders_always are accessed
"huge_anon_orders_always" mentioned twice.
> lockless, it is better to use the READ_ONCE() wrapper.
> This is not fixing any visible bug, hopefully this can cease some
> KCSAN complains in the future.
> Also do that for huge_anon_orders_madvise.
>
> Signed-off-by: Ran Xiaokai <[email protected]>
> ---
> include/linux/huge_mm.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index de0c89105076..6573430ea600 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -122,8 +122,8 @@ static inline bool hugepage_flags_enabled(void)
> * So we don't need to look at huge_anon_orders_inherit.
> */
> return hugepage_global_enabled() ||
> - huge_anon_orders_always ||
> - huge_anon_orders_madvise;
> + READ_ONCE(huge_anon_orders_always) ||
> + READ_ONCE(huge_anon_orders_madvise);
Don't mess up the alignment please.
> }
>
> static inline int highest_order(unsigned long orders)
Acked-by: David Hildenbrand <[email protected]>
--
Cheers,
David / dhildenb
On Sat, May 11, 2024 at 12:44 AM <[email protected]> wrote:
>
> From: Ran Xiaokai <[email protected]>
>
> huge_anon_orders_always and huge_anon_orders_always are accessed
> lockless, it is better to use the READ_ONCE() wrapper.
> This is not fixing any visible bug, hopefully this can cease some
> KCSAN complains in the future.
A little bit confused here. Did you see complaints from KCSAN?
> Also do that for huge_anon_orders_madvise.
>
> Signed-off-by: Ran Xiaokai <[email protected]>
> ---
> include/linux/huge_mm.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index de0c89105076..6573430ea600 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -122,8 +122,8 @@ static inline bool hugepage_flags_enabled(void)
> * So we don't need to look at huge_anon_orders_inherit.
> */
> return hugepage_global_enabled() ||
> - huge_anon_orders_always ||
> - huge_anon_orders_madvise;
> + READ_ONCE(huge_anon_orders_always) ||
> + READ_ONCE(huge_anon_orders_madvise);
> }
>
> static inline int highest_order(unsigned long orders)
> --
> 2.15.2
>>
>> From: Ran Xiaokai <[email protected]>
>>
>> huge_anon_orders_always and huge_anon_orders_always are accessed
>> lockless, it is better to use the READ_ONCE() wrapper.
>> This is not fixing any visible bug, hopefully this can cease some
>> KCSAN complains in the future.
>
> A little bit confused here. Did you see complaints from KCSAN?
Not yet.
The only written access to huge_anon_orders_always is when
changing the mTHP sysfs "enabled" knob, I think peple do not
change the mTHP settings frequently.
But the possibility is not zero, please refer to the cgroup related knobs,
I think wde'd better do the same and this annotation wont lead to any performance issue, right?
>> Also do that for huge_anon_orders_madvise.
>>
>> Signed-off-by: Ran Xiaokai <[email protected]>
>> ---
>> include/linux/huge_mm.h | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index de0c89105076..6573430ea600 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -122,8 +122,8 @@ static inline bool hugepage_flags_enabled(void)
>> * So we don't need to look at huge_anon_orders_inherit.
>> */
>> return hugepage_global_enabled() ||
>> - huge_anon_orders_always ||
>> - huge_anon_orders_madvise;
>> + READ_ONCE(huge_anon_orders_always) ||
>> + READ_ONCE(huge_anon_orders_madvise);
>> }
>>
>> static inline int highest_order(unsigned long orders)
Hi, David
Thanks for taking time to review!
>> From: Ran Xiaokai <[email protected]>
>>
>> huge_anon_orders_always and huge_anon_orders_always are accessed
>
> "huge_anon_orders_always" mentioned twice.
yes, my mistake.
>> lockless, it is better to use the READ_ONCE() wrapper.
>> This is not fixing any visible bug, hopefully this can cease some
>> KCSAN complains in the future.
>> Also do that for huge_anon_orders_madvise.
>>
>> Signed-off-by: Ran Xiaokai <[email protected]>
>> ---
>> include/linux/huge_mm.h | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index de0c89105076..6573430ea600 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -122,8 +122,8 @@ static inline bool hugepage_flags_enabled(void)
>> * So we don't need to look at huge_anon_orders_inherit.
>> */
>> return hugepage_global_enabled() ||
>> - huge_anon_orders_always ||
>> - huge_anon_orders_madvise;
>> + READ_ONCE(huge_anon_orders_always) ||
>> + READ_ONCE(huge_anon_orders_madvise);
>
> Don't mess up the alignment please.
yes.
I will wait for other feedbacks and then send out a v2 version.
>> }
>>
>> static inline int highest_order(unsigned long orders)
>
> Acked-by: David Hildenbrand <[email protected]>