On Thu, Dec 01, 2022 at 07:35:59AM +0900, Masahiro Yamada wrote:
> On Wed, Nov 30, 2022 at 4:02 AM Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
> >
> > When building arm64 allmodconfig + ThinLTO with clang and a proposed
> > modpost update to account for -ffuncton-sections, the following warning
> > appears:
> >
> > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text)
> > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text)
> >
> > In both cases, an __init function calls padata_work_init(), which is not
> > marked __init, with padata_mt_helper(), another __init function, as a
> > work function argument.
> >
> > padata_work_init() is called from non-init paths, otherwise it could be
> > marked __init to resolve the warning. Instead, remove __init from
> > padata_mt_helper() to resolve the warning.
> >
> > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> > ---
> > Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
> > Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> > Cc: linux-crypto@xxxxxxxxxxxxxxx
> > ---
> > kernel/padata.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/padata.c b/kernel/padata.c
> > index e5819bb8bd1d..c2271d7e446d 100644
> > --- a/kernel/padata.c
> > +++ b/kernel/padata.c
> > @@ -45,7 +45,7 @@ struct padata_mt_job_state {
> > };
> >
> > static void padata_free_pd(struct parallel_data *pd);
> > -static void __init padata_mt_helper(struct work_struct *work);
> > +static void padata_mt_helper(struct work_struct *work);
> >
> > static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
> > {
> > @@ -425,7 +425,7 @@ static int padata_setup_cpumasks(struct padata_instance *pinst)
> > return err;
> > }
> >
> > -static void __init padata_mt_helper(struct work_struct *w)
> > +static void padata_mt_helper(struct work_struct *w)
> > {
> > struct padata_work *pw = container_of(w, struct padata_work, pw_work);
> > struct padata_mt_job_state *ps = pw->pw_data;
> > --
> > 2.38.1
> >
>
> This patch seems wrong.
>
> padata_work_init() does not reference to padata_mt_helper()
>
>
> padata_work_alloc_mt() and padata_do_multithreaded() do.
I see LLVM optimizing padata_work_init by embedding padata_mt_helper's
address in its text, which runs afoul of modpost.
I agree with Masahiro, the warning is a false positive since only __init
functions ever cause the embedded address to be used.
We have __ref for situations like this. That way, padata_mt_helper can
stay properly __init.
