Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

Peter Zijlstra
2016-06-23T19:11:42Z

On Thu, Jun 23, 2016 at 04:31:26PM +0200, Oleg Nesterov wrote:
> On 06/22, Linus Torvalds wrote:
> >
> > Oleg, what do you think? Would it be reasonable to free the stack and
> > thread_info synchronously at exit time, clear the pointer (to catch
> > any odd use), and only RCU-delay the task_struct itself?
>
> I didn't see the patches yet, quite possibly I misunderstood... But no,
> I don't this we can do this (if we are not going to move ti->flags to
> task_struct at least).

Didn't we talk about using SLAB_DESTROY_BY_RCU for task_struct before?
If that is possible, a reuse in per-cpu cache is equally possible.

All we really want to guarantee is that the memory remains a
task_struct, it need not remain the same task, right?