linux-kernel - Re: [PATCH 3/3] thread_info: include <current.h> for THREAD_INFO_IN

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Message-Id: <20161020102925.GA3529@osiris>
Date:   Thu, 20 Oct 2016 12:29:26 +0200
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        akpm@...ux-foundation.org, hpa@...or.com, keescook@...omium.org,
        luto@...nel.org, mingo@...hat.com, tglx@...utronix.de
Subject: Re: [PATCH 3/3] thread_info: include <current.h> for
 THREAD_INFO_IN_TASK

On Wed, Oct 19, 2016 at 07:28:13PM +0100, Mark Rutland wrote:
> When CONFIG_THREAD_INFO_IN_TASK is selected, the current_thread_info()
> macro relies on current having been defined prior to its use. However,
> not all users of current_thread_info() include <asm/current.h>, and thus
> current is not guaranteed to be defined.
> 
> When CONFIG_THREAD_INFO_IN_TASK is not selected, it's possible that
> get_current() / current are based upon current_thread_info(), and
> <asm/current.h> includes <asm/thread_info.h>. Thus always including
> <asm/current.h> would result in circular dependences on some platforms.
> 
> To ensure both cases work, this patch includes <asm/current.h>, but only
> when CONFIG_THREAD_INFO_IN_TASK is selected.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Kees Cook <keescook@...omium.org> 
> ---
>  include/linux/thread_info.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
> index c75c6ab..ef1f4b0 100644
> --- a/include/linux/thread_info.h
> +++ b/include/linux/thread_info.h
> @@ -12,6 +12,7 @@
>  #include <linux/restart_block.h>
>  
>  #ifdef CONFIG_THREAD_INFO_IN_TASK
> +#include <asm/current.h>
>  #define current_thread_info() ((struct thread_info *)current)
>  #endif

FWIW:
Acked-by: Heiko Carstens <heiko.carstens@...ibm.com>