On Wed, 20 Sep 2006 11:57:09 +1000
Benjamin Herrenschmidt <[email protected]> wrote:
> > You forget that the point of this optimisation is to undo mmap_sem while
> > waiting on the disk IO. Once we've done that we cannot go looking at ptes
> > or vmas: another thread could have munapped the whole lot or anything.
> > (And we always need to be afraid of use_mm()..)
>
> Wait wait .. .we don't need to have the mmap sem to -look- at a PTE.
The pte resides in a pagetable page. Once we've dropped mmap_sem, that
pagetable page might not be there any more: munmap() might have freed it.
We have to retake mmap_sem, do a find_vma() and a new pagetable walk.
There are some optimisations we could make to avoid all of that in the
common case, but this is the conceptual behaviour.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
