Re: [PATCH] m68k: Fix task info flags handling for 68000

Hi Greg,

On Mon, 16 Mar 2026 at 23:08, Greg Ungerer <[email protected]> wrote:
>
> The comments from arch/m68k/include/asm/thread_info.h are this:
>
> /* entry.S relies on these definitions!
>   * bits 0-7 are tested at every exception exit
>   * bits 8-15 are also tested at syscall exit
>   */
>
> So looking at what check is in arch/m68k/coldfire/entry.S:
>
>      moveb   %a0@(TINFO_FLAGS+3),%d1 /* thread_info->flags (low 8 bits) */
>
> In arch/m68k/kernel/entry.S it looks to be doing basically the same thing:
>
>      moveb   %a1@(TINFO_FLAGS+3),%d0
>
> So they do really only check bits 0-7 here.
>
> If you code the check like that do you still get correct running behavior?

That seems to work. One thing I'm unsure about is this in the coldfire version:

Luser_return:
movel %sp,%d1 /* get thread_info pointer */
andl #-THREAD_SIZE,%d1 /* at base of kernel stack */
movel %d1,%a0
moveb %a0@(TINFO_FLAGS+3),%d1 /* thread_info->flags (low 8 bits) */

^^^^^^
So the bottom 8 bits are in d1

jne Lwork_to_do /* still work to do */

Lreturn:
RESTORE_USER

Lwork_to_do:
movel %a0@(TINFO_FLAGS),%d1 /* get thread_info->flags */

^^^^^^^
Now the whole value is loaded into d1 to do the bit test.. but the
value needed is already in d1 as we'll be testing bit 7?

move #0x2000,%sr /* enable intrs again */
btst #TIF_NEED_RESCHED,%d1
jne reschedule


Thanks,

Daniel