On Tue, Aug 19, 2025 at 8:32 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Tue, Aug 19, 2025 at 09:58:31AM +0800, Menglong Dong wrote:
>
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index be00629f0ba4..00383fed9f63 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -119,6 +119,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
> > EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);
> >
> > DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
> > +EXPORT_SYMBOL_GPL(runqueues);
>
> Oh no, absolutely not.
>
> You never, ever, export a variable, and certainly not this one.
>
> How about something like so?
>
> I tried 'clever' things with export inline, but the compiler hates me,
> so the below is the best I could make work.
I see. You mean that we don't export the various, and use the
inlined version in vmlinux, and use the external version in modules,
which I think is nice ;)
(I were not aware that we should export various :/)
I'll try your advice.
Thanks!
Menglong Dong
>
> ---
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2315,6 +2315,7 @@ static __always_inline void alloc_tag_re
> #define alloc_tag_restore(_tag, _old) do {} while (0)
> #endif
>
> +#ifndef MODULE
> #ifndef COMPILE_OFFSETS
>
> extern void __migrate_enable(void);
> @@ -2328,7 +2329,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq
> #define this_rq_raw() PERCPU_PTR(&runqueues)
> #endif
>
> -static inline void migrate_enable(void)
> +static inline void _migrate_enable(void)
> {
> struct task_struct *p = current;
>
> @@ -2363,7 +2364,7 @@ static inline void migrate_enable(void)
> (*(unsigned int *)((void *)this_rq_raw() + RQ_nr_pinned))--;
> }
>
> -static inline void migrate_disable(void)
> +static inline void _migrate_disable(void)
> {
> struct task_struct *p = current;
>
> @@ -2382,10 +2383,30 @@ static inline void migrate_disable(void)
> (*(unsigned int *)((void *)this_rq_raw() + RQ_nr_pinned))++;
> p->migration_disabled = 1;
> }
> -#else
> -static inline void migrate_disable(void) { }
> -static inline void migrate_enable(void) { }
> -#endif
> +#else /* !COMPILE_OFFSETS */
> +static inline void _migrate_disable(void) { }
> +static inline void _migrate_enable(void) { }
> +#endif /* !COMPILE_OFFSETS */
> +
> +#ifndef CREATE_MIGRATE_DISABLE
> +static inline void migrate_disable(void)
> +{
> + _migrate_disable();
> +}
> +
> +static inline void migrate_enable(void)
> +{
> + _migrate_enable();
> +}
> +#else /* CREATE_MIGRATE_DISABLE */
> +extern void migrate_disable(void);
> +extern void migrate_enable(void);
> +#endif /* CREATE_MIGRATE_DISABLE */
> +
> +#else /* !MODULE */
> +extern void migrate_disable(void);
> +extern void migrate_enable(void);
> +#endif /* !MODULE */
>
> DEFINE_LOCK_GUARD_0(migrate, migrate_disable(), migrate_enable())
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7,6 +7,9 @@
> * Copyright (C) 1991-2002 Linus Torvalds
> * Copyright (C) 1998-2024 Ingo Molnar, Red Hat
> */
> +#define CREATE_MIGRATE_DISABLE
> +#include <linux/sched.h>
> +
> #include <linux/highmem.h>
> #include <linux/hrtimer_api.h>
> #include <linux/ktime_api.h>
> @@ -119,7 +122,6 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_updat
> EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);
>
> DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
> -EXPORT_SYMBOL_GPL(runqueues);
>
> #ifdef CONFIG_SCHED_PROXY_EXEC
> DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec);
> @@ -2382,6 +2384,11 @@ static void migrate_disable_switch(struc
> __do_set_cpus_allowed(p, &ac);
> }
>
> +void migrate_disable(void)
> +{
> + _migrate_disable();
> +}
> +
> void __migrate_enable(void)
> {
> struct task_struct *p = current;
> @@ -2392,7 +2399,11 @@ void __migrate_enable(void)
>
> __set_cpus_allowed_ptr(p, &ac);
> }
> -EXPORT_SYMBOL_GPL(__migrate_enable);
> +
> +void migrate_enable(void)
> +{
> + _migrate_enable();
> +}
>
> static inline bool rq_has_pinned_tasks(struct rq *rq)
> {
