Re: [PATCH v2] ipc/sem: do not sleep with a spin lock held

[Shakeel Butt]

On Mon, Jan 3, 2022 at 9:18 AM Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> wrote:
>
> Hi Jiri,
>
> On 1/3/22 10:27, Jiri Slaby wrote:
> > On 23. 12. 21, 4:12, cgel.zte@xxxxxxxxx wrote:
> >> From: Minghao Chi <chi.minghao@xxxxxxxxxx>
> >>
> >> We can't call kvfree() with a spin lock held, so defer it.
> >
> > Sorry, defer what?
> >
> First drop the spinlock, then call kvfree().
>
>
> > There are attempts to fix kvfree instead, not sure which of these
> > approaches (fix kvfree or its callers) won in the end?
> >
> Exactly. We have three options - but noone volunteered yet to decide:
>
> - change ipc/sem.c [minimal change]

Let's go with the minimal change for now which can easily be
cherry-picked for the stable tree. It seems other approaches need more
work/discussion.

>
> - change kvfree() to use vfree_atomic() [would also fix other changes
> that did s/kfree/kvfree/]
>
> - Modify the vma handling so that it becomes safe to call vfree() while
> holding a spinlock. [perfect approach, but I'm concerned about side effects]
>
>
> --
>
>      Manfred
>