Re: [PATCH 0/2] completion: Reduce stack usage caused by COMPLETION_INITIALIZER_ONSTACK()

[Arnd Bergmann]

On Wed, Aug 23, 2017 at 5:25 PM, Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
> With LOCKDEP_CROSSRELEASE and LOCKDEP_COMPLETIONS introduced, the growth
> in kernel stack usage of several functions were reported:
>
>         https://marc.info/?l=linux-kernel&m=150270063231284&w=2
>
> The root cause of this is in COMPLETION_INITIALIZER_ONSTACK(), we use
>
>         ({init_completion(&work); work})
>
> , which will create a temporary object when returned. However this
> temporary object is unnecessary. And this patch fixes it by making the
> statement expression in COMPLETION_INITIALIZER_ONSTACK() return a
> pointer rather than a whole structure. This will reduce the stack usage
> even if !LOCKDEP.
>
> However, such a change does make one COMPLETION_INITIALIZER_ONSTACK()
> callsite invalid, so we fix this first via converting to
> init_completion().

Both patches

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>