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

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.

> ---
>  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