(also resending this reply from @kernel.org)

On Fri, Oct 16, 2020 at 12:19 PM Arnd Bergmann [off-list ref] wrote:

On Thu, Oct 8, 2020 at 9:20 AM Maninder Singh [off-list ref] wrote:

quoted

This patch adds code for switching to IRQ stack.
IRQ stack and Kernel SVC stack have below design.

IRQ STACK:-
                    ------------ IRQ stack top
                    |          |
                    ------------
                    .          .
                    .          .
                    .          .
                    ------------
                    |    sp    | <- irq_stack_base + 0x8
                    ------------
                    |    fp    | <- irq_stack_base + 0x4
                    ------------
                    |tinfo_ptr | /* pointer to thread info */
irq_stack_ptr -->   ------------ IRQ stack base

Kernel SVC stack:-
                    ------------  Kernel stack top
                    |          |
                    ------------
                    .          .
                    .          .
                    .          .
                    ------------
                    |          |
                    |          |
                    ------------
                    |tinfo_ptr |  /* pointer to thread info */
                    ------------ Kernel stack base

The extra indirection doesn't look great, and I don't see any of the
other architectures need that. Since we can access percpu data
without going through thread_info, maybe doing the same as
x86 would work here:

- define 'current' as 'this_cpu_read_stable(current_task);'
- convert to CONFIG_THREAD_INFO_IN_TASK

       Arnd

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel