sched_ext: Implement SCX_KICK_WAIT

If set when calling scx_bpf_kick_cpu(), the invoking CPU will busy wait for
the kicked cpu to enter the scheduler. See the following for example usage:

  https://github.com/sched-ext/scx/blob/main/scheds/c/scx_pair.bpf.c

v2: - Updated to fit the updated kick_cpus_irq_workfn() implementation.

    - Include SCX_KICK_WAIT related information in debug dump.

Signed-off-by: David Vernet <dvernet@meta.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h
index 6ed946f72489..0aeb1fda1794 100644
--- a/kernel/sched/ext.h
+++ b/kernel/sched/ext.h
@@ -29,6 +29,8 @@ static inline bool task_on_scx(const struct task_struct *p)
 	return scx_enabled() && p->sched_class == &ext_sched_class;
 }
 
+void scx_next_task_picked(struct rq *rq, struct task_struct *p,
+			  const struct sched_class *active);
 void scx_tick(struct rq *rq);
 void init_scx_entity(struct sched_ext_entity *scx);
 void scx_pre_fork(struct task_struct *p);
@@ -69,6 +71,8 @@ static inline const struct sched_class *next_active_class(const struct sched_cla
 #define scx_enabled()		false
 #define scx_switched_all()	false
 
+static inline void scx_next_task_picked(struct rq *rq, struct task_struct *p,
+					const struct sched_class *active) {}
 static inline void scx_tick(struct rq *rq) {}
 static inline void scx_pre_fork(struct task_struct *p) {}
 static inline int scx_fork(struct task_struct *p) { return 0; }