Re: [PATCH] mk68k: Fix broken THREAD_SIZE_ORDER

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Hi Dawei,

On Wed, Feb 28, 2024 at 10:34 AM Dawei Li <dawei.li@xxxxxxxxxxxx> wrote:
On Wed, Feb 28, 2024 at 10:11:05AM +0100, Jiri Slaby wrote:
On 28. 02. 24, 9:58, Dawei Li wrote:
Current THREAD_SIZE_ORDER implementation for m68k is incorrect, fix it
by ilog2().

This is not a good commit log. Incorrect in what way and why is the fixed

Agreed.

version correct? And what is affected? Note you're referring to a change
which was done 14 years ago. It definitely must not be that incorrect (for
everybody).

It's 'right' just for current PAGE_SIZE & THREAD_SIZE configs:

// arch/m68k/include/asm/thread_info.h
#if PAGE_SHIFT < 13
#ifdef CONFIG_4KSTACKS
#define THREAD_SIZE     4096
#else
#define THREAD_SIZE     8192
#endif
#else
#define THREAD_SIZE     PAGE_SIZE
#endif
#define THREAD_SIZE_ORDER       ((THREAD_SIZE / PAGE_SIZE) - 1)

Indeed.  The only supported values for THREAD_SIZE_ORDER on m68k are
0 and 1.

But it's incorrect in generic/mathematical way.

True.  But does it matter much?
I.e. do you plan to add support for larger values of THREAD_SIZE?

What about changing the #ifdeffery to set THREAD_SIZE_ORDER to an
explicit value, and calculating THREAD_SIZE from THREAD_SIZE_ORDER
instead?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds





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