Re: [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances

[Linus Torvalds]

On Wed, Feb 12, 2020 at 12:41 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Feb 12, 2020 at 08:38:33PM +0000, Al Viro wrote:
> >
> > Wait, I thought the whole point of that had been to allow multiple
> > procfs instances for the same userns?  Confused...
>
> s/userns/pidns/, sorry

Right, but we still hold the ref to it here...

[ Looks more ]

Oooh. No we don't. Exactly because we don't hold the lock, only the
rcu lifetime, the ref can go away from under us. I see what your
concern is.

Ouch, this is more painful than I expected - the code flow looked so
simple. I really wanted to avoid a new lock during process shutdown,
because that has always been somewhat painful.

            Linus