[PATCH 4/4] Do not call flush_cache_user_range with mmap_sem held

[Russell King - ARM Linux]

On Mon, Apr 04, 2011 at 02:27:45PM +0100, Catalin Marinas wrote:
> Russell,
> 
> On 14 December 2010 21:08, Catalin Marinas <catalin.marinas at arm.com> wrote:
> > On Tuesday, 14 December 2010, Russell King - ARM Linux
> > <linux at arm.linux.org.uk> wrote:
> >> On Tue, Dec 14, 2010 at 05:51:36PM +0000, Catalin Marinas wrote:
> >>> But what's the problem if such mapping disappears? The
> >>> flush_cache_user_range code should just skip such pages.
> >>
> >> That's only half the story.
> >>
> >> What if someone remaps something over that range before the cache
> >> maintainence has completed.
> >
> > That someone remapping the same range can only be a thread of the same
> > process. If the code was so badly written as to unmap ranges of memory
> > when a thread actively uses it, then it probably deserves any
> > corruption.
> 
> I haven't seen any more replies in this thread but I still think it's
> a real problem as John reported. Do you agree with the original patch?

No, I do not agree.