linux-kernel - Re: [Bug 214661] New: THREAD_SIZE on x86_64 is 4*PAGE_SIZE, not 2*PAGE

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Message-ID: <3078967c-cde6-198f-4c2d-66a635a622c1@gmail.com>
Date:   Sat, 9 Oct 2021 20:51:25 +0200
From:   "Alejandro Colomar (man-pages)" <alx.manpages@...il.com>
To:     bugzilla-daemon@...zilla.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Bug 214661] New: THREAD_SIZE on x86_64 is 4*PAGE_SIZE, not
 2*PAGE_SIZE

CC += LKML

Hello,

On 10/9/21 7:19 AM, bugzilla-daemon@...zilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=214661
> 
>              Bug ID: 214661
>             Summary: THREAD_SIZE on x86_64 is 4*PAGE_SIZE, not 2*PAGE_SIZE
>             Product: Documentation
>             Version: unspecified
>            Hardware: All
>                  OS: Linux
>              Status: NEW
>            Severity: normal
>            Priority: P1
>           Component: man-pages

This is incorrect.

The internal kernel documentation is not part of the man-pages.
I checked to see if the manual pages need an update, but I couldn't find 
anything about THREAD_SIZE:

alx@...i:~/src/linux/man-pages$ grep -rn THREAD_SIZE
alx@...i:~/src/linux/man-pages$

I can't edit the component, so maybe you need to close the bug and open 
a new one in a different component.

Anyway, thanks for the report!

Alex


>            Assignee: documentation_man-pages@...nel-bugs.osdl.org
>            Reporter: me@...vee.com
>          Regression: No
> 
> According to '/root/linux/arch/x86/include/asm/page_64_types.h', THREAD_SIZE on
> x86_64 now is 4*PAGE_SIZE:
> 
> #ifdef CONFIG_KASAN
> #define KASAN_STACK_ORDER 1
> #else
> #define KASAN_STACK_ORDER 0
> #endif
> 
> #define THREAD_SIZE_ORDER       (2 + KASAN_STACK_ORDER)
> #define THREAD_SIZE  (PAGE_SIZE << THREAD_SIZE_ORDER)
> 
> However, the Documentation/x86/kernel-stacks.rst shows that THREAD_SIZE on
> x86_64 is 2*PAGE_SIZE:
> 
> Like all other architectures, x86_64 has a kernel stack for every
> active thread.  These thread stacks are THREAD_SIZE (2*PAGE_SIZE) big.
> 
> I am not quite sure which is correct, Maybe the document needs an upgrade?
> Thanks a lot for any reply.
> 


-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/