On Fri, 2025-07-11 at 14:50 +0800, Tiwei Bie wrote:
> From: Tiwei Bie <tiwei....@antgroup.com>
>
> The PID of the stub process can be obtained from current_mm_id().
> There is no need to track it via userspace_pid[]. Stop doing that
> to simplify the code.
So that is really obvious cleanups, and I can go apply them on that
grounds, but I started wondering if we're not separately being
inconsistent here, which perhaps didn't matter due to non-SMP:
> #define activate_mm activate_mm
> static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
> {
> - /*
> - * This is called by fs/exec.c and sys_unshare()
> - * when the new ->mm is used for the first time.
> - */
> - __switch_mm(&new->context.id);
> }
This is now empty, so I wondered if we can just remove it _entirely_.
But the generic version calls switch_mm():
> static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
> @@ -28,11 +23,9 @@ static inline void switch_mm(struct mm_struct *prev,
> struct mm_struct *next,
> {
> unsigned cpu = smp_processor_id();
>
> - if(prev != next){
> + if (prev != next) {
> cpumask_clear_cpu(cpu, mm_cpumask(prev));
> cpumask_set_cpu(cpu, mm_cpumask(next));
> - if(next != &init_mm)
> - __switch_mm(&next->context.id);
> }
> }
which plays with the CPU mask, but realistically being non-SMP the CPU
mask is never really used?
Certainly removing activate_mm() entirely seems to _work_, but of course
it never does anything since smp_processor_id() eventually is just
macros that expand to "0" (unless preempt debug is enabled). Any
thoughts?
johannes
