Re: return value of ptep_get_and_clear

[Brian Gerst]

Kumar Gala wrote:
> ptep_get_and_clear has a signature that looks something like:
>
> static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned 
> long addr,
>                                        pte_t *ptep)
>
> It appears that its suppose to return the pte_t pointed to by ptep 
> before its modified.  Why do we bother doing this?  The caller seems 
> perfectly able to dereference ptep and hold on to it.  Am I missing 
> something here?
>
> If not, I'll work up a set of patches to change ptep_get_and_clear and 
> its callers for post 2.6.12 release.
>
> - kumar

Because it is an atomic operation.  If you dereference it before 
ptep_get_and_clear() it could change in between.

--
				Brian Gerst
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/