Re: [PATCH] init/Kconfig: Update the THREAD_INFO_IN_TASK description

Hi, Nathan,

On Tue, Jun 9, 2026 at 5:46 AM Nathan Chancellor <[email protected]> wrote:
>
> Hi Huacai,
>
> On Sat, Jun 06, 2026 at 05:25:01PM +0800, Huacai Chen wrote:
> > When commit c65eacbe290b81 ("sched/core: Allow putting thread_info into
> > task_struct") introduces THREAD_INFO_IN_TASK in 4.9, the only supported
> > architecture is x86 and thread_info only has a flags field. The Kconfig
> > description said thread_info should only has the flags field but didn't
> > explain the reason.
> >
> > When commit c02433dd6de32f ("arm64: split thread_info from task stack")
> > introduces THREAD_INFO_IN_TASK for arm64 in 4.10, its thread_info has
> > more fields than a single flags, and arm64 works well.
> >
> > Then commit 37a8f7c38339b2 ("x86/asm: Move 'status' from thread_struct
> > to thread_info") adds status back to thread_info for x86 in 4.16, and
> > x86 still works well.
> >
> > After that, risc-v, powerpc and many other architectures all introduce
> > THREAD_INFO_IN_TASK and their thread_info have more fields rather than
> > a single flags field, of course they also work well.
> >
> > I don't know the exact reason of the original description, but obviously
> > it is wrong and misleading, so I update it, let LoongArch and some other
> > architectures easier to support THREAD_INFO_IN_TASK.
> >
> > Also improve the try_get_task_stack() and put_task_stack() description.
> >
> > Signed-off-by: Huacai Chen <[email protected]>
>
> You addressed this to Kbuild folks but I don't really think this is our
> domain. I think you would be better off sending this to the scheduler
> folks or Andrew Morton.
OK, I will resend it to scheduler. Thanks.

Huacai

>
> > ---
> >  init/Kconfig | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 2937c4d308ae..a9466879d553 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -207,11 +207,12 @@ config THREAD_INFO_IN_TASK
> >       bool
> >       help
> >         Select this to move thread_info off the stack into task_struct.  To
> > -       make this work, an arch will need to remove all thread_info fields
> > -       except flags and fix any runtime bugs.
> > +       make this work, an arch will need to remove the task_struct pointer
> > +       field from thread_info and fix any runtime bugs.
> >
> >         One subtle change that will be needed is to use try_get_task_stack()
> > -       and put_task_stack() in save_thread_stack_tsk() and get_wchan().
> > +       and put_task_stack() in save_thread_stack_tsk(), get_wchan() and any
> > +       other stacktrace functions.
> >
> >  menu "General setup"
> >
> > --
> > 2.52.0
> >
>
> --
> Cheers,
> Nathan