[PATCH v6 14/16] sched_ext: Export task_is_scx_enabled() for verification

[Gabriele Monaco <gmonaco@redhat.com>]

When a sched_ext scheduler is loaded, depending on the configuration, it
can handle also fair tasks, however it isn't trivial to understand if a
certain task is currently handled by fair or ext outside of scheduler
code. This can be a problem when writing verification or observability
tools like RV monitors.

Export a task_is_scx_enabled() to allow quick classification by using
the scx state SCX_TASK_ENABLED.

To: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
---
 include/linux/sched/ext.h | 2 ++
 kernel/sched/ext.c        | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h
index bcb962d5ee7d..68e5aff95159 100644
--- a/include/linux/sched/ext.h
+++ b/include/linux/sched/ext.h
@@ -232,6 +232,7 @@ void print_scx_info(const char *log_lvl, struct task_struct *p);
 void scx_softlockup(u32 dur_s);
 bool scx_hardlockup(int cpu);
 bool scx_rcu_cpu_stall(void);
+bool task_is_scx_enabled(struct task_struct *p);
 
 #else	/* !CONFIG_SCHED_CLASS_EXT */
 
@@ -240,6 +241,7 @@ static inline void print_scx_info(const char *log_lvl, struct task_struct *p) {}
 static inline void scx_softlockup(u32 dur_s) {}
 static inline bool scx_hardlockup(int cpu) { return false; }
 static inline bool scx_rcu_cpu_stall(void) { return false; }
+static inline bool task_is_scx_enabled(struct task_struct *p) { return false; }
 
 #endif	/* CONFIG_SCHED_CLASS_EXT */
 
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 62b1f3ac5630..1e48bc3cde15 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3772,6 +3772,14 @@ bool task_should_scx(int policy)
 	return policy == SCHED_EXT;
 }
 
+/*
+ * Used by verification/observability tools like RV monitors.
+ */
+bool task_is_scx_enabled(struct task_struct *p)
+{
+	return scx_get_task_state(p) == SCX_TASK_ENABLED;
+}
+
 bool scx_allow_ttwu_queue(const struct task_struct *p)
 {
 	struct scx_sched *sch;
-- 
2.53.0