On Fri, Feb 21, 2014 at 12:57 PM, Davidlohr Bueso <davidlohr@xxxxxx> wrote:
>
> Btw, one concern I had is regarding seqnum overflows... if such
> scenarios should happen we'd end up potentially returning bogus vmas and
> getting bus errors and other sorts of issues. So we'd have to flush the
> caches, but, do we care? I guess on 32bit systems it could be a bit more
> possible to trigger given enough forking.
I guess we should do something like
if (unlikely(!++seqnum))
flush_vma_cache()
just to not have to worry about it.
And we can either use a "#ifndef CONFIG_64BIT" to disable it for the
64-bit case (because no, we really don't need to worry about overflow
in 64 bits ;), or just decide that a 32-bit sequence number actually
packs better in the structures, and make it be an "u32" even on 64-bit
architectures?
It looks like a 32-bit sequence number might pack nicely next to the
unsigned brk_randomized:1;
but I didn't actually go and look at the context there to see what
else is there..
Linus
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>