[PATCH 07/39] sched: Expose css_tg() and __setscheduler_prio()

Tejun Heo
2024-05-01T15:13:31Z

These will be used by a new BPF extensible sched_class.

css_tg() will be used in the init and exit paths to visit all task_groups by
walking cgroups.

__setscheduler_prio() is used to pick the sched_class matching the current
prio of the task. For the new BPF extensible sched_class, the mapping from
the task configuration to sched_class isn't static and depends on a few
factors - e.g. whether the BPF progs implementing the scheduler are loaded
and in a serviceable state. That mapping logic will be added to
__setscheduler_prio().

When the BPF scheduler progs get loaded and unloaded, the mapping changes
and the new sched_class will walk the tasks applying the new mapping using
__setscheduler_prio().

v3: Dropped SCHED_CHANGE_BLOCK() as upstream is adding more generic cleanup
mechanism.

v2: Expose SCHED_CHANGE_BLOCK() too and update the description.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
Reported-by: kernel test robot <lkp@intel.com>
---
kernel/sched/core.c | 7 +------
kernel/sched/sched.h | 7 +++++++
2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9b60df944263..987209c0e672 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7098,7 +7098,7 @@ int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flag
}
EXPORT_SYMBOL(default_wake_function);

-static void __setscheduler_prio(struct task_struct *p, int prio)
+void __setscheduler_prio(struct task_struct *p, int prio)
{
if (dl_prio(prio))
p->sched_class = &dl_sched_class;
@@ -10542,11 +10542,6 @@ void sched_move_task(struct task_struct *tsk)
}
}

-static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
-{
- return css ? container_of(css, struct task_group, css) : NULL;
-}
-
static struct cgroup_subsys_state *
cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
{
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 24b3d120700b..7e0de4cb5a52 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -477,6 +477,11 @@ static inline int walk_tg_tree(tg_visitor down, tg_visitor up, void *data)
return walk_tg_tree_from(&root_task_group, down, up, data);
}

+static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
+{
+ return css ? container_of(css, struct task_group, css) : NULL;
+}
+
extern int tg_nop(struct task_group *tg, void *data);

#ifdef CONFIG_FAIR_GROUP_SCHED
@@ -2481,6 +2486,8 @@ extern void init_sched_dl_class(void);
extern void init_sched_rt_class(void);
extern void init_sched_fair_class(void);

+extern void __setscheduler_prio(struct task_struct *p, int prio);
+
extern void resched_curr(struct rq *rq);
extern void resched_cpu(int cpu);

--
2.44.0