Re: kernel-side thread stack swapping

On Fri, Sep 02, 2022 at 04:11:40PM +0200, Mateusz Guzik wrote:
> On 9/2/22, Konstantin Belousov <kostikbel@gmail.com> wrote:
> > On Fri, Sep 02, 2022 at 02:05:37PM +0200, Mateusz Guzik wrote:
> >> Is this really of practical use today?
> >>
> >> I have a WIP patch which needs to temporarily store something on the
> >> stack and should things go wrong enough it will be accessed by UMA,
> >> which can't handle the fault nor decide to skip the access.
> >>
> >> I can add something like td_pinstack or whatever to keep it around,
> >> but perhaps the entire machinery can be just whacked?
> > p_hold already does that.
> >
> 
> I only need to protect the one stack and more importantly don't want
> to take the proc lock to bump p_hold (nor convert it to atomics), it's
> all thread-local so to speak.

You do not want to take proc lock, or cannot?  Note that only sleeping
thread' stack can be swapped out.