Re: [PATCH v2 1/2] mmap locking API: add mmap_lock_is_contended()

[Steven Price <steven.price@arm.com>]

On 13/08/2020 03:13, Chinwen Chang wrote:
> Add new API to query if someone wants to acquire mmap_lock
> for write attempts.
> 
> Using this instead of rwsem_is_contended makes it more tolerant
> of future changes to the lock type.
> 
> Signed-off-by: Chinwen Chang <chinwen.chang@mediatek.com>

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
>   include/linux/mmap_lock.h | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
> index 0707671..18e7eae 100644
> --- a/include/linux/mmap_lock.h
> +++ b/include/linux/mmap_lock.h
> @@ -87,4 +87,9 @@ static inline void mmap_assert_write_locked(struct mm_struct *mm)
>   	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
>   }
>   
> +static inline int mmap_lock_is_contended(struct mm_struct *mm)
> +{
> +	return rwsem_is_contended(&mm->mmap_lock);
> +}
> +
>   #endif /* _LINUX_MMAP_LOCK_H */
>