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Subject[RFC PATCH 1/3] sched/core: Provide a method to check if a task is PI-boosted.
Date
Provide a method to check if a task inherited the priority from another
task. This happens if a task owns a lock which is requested by a task
with higher priority. This can be used as a hint to add a preemption
point to the critical section.

Provide a function which reports true if the task is PI-boosted.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/sched.h | 1 +
kernel/sched/core.c | 15 +++++++++++++++
2 files changed, 16 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 609bde814cb06..77fd274133750 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1887,6 +1887,7 @@ static inline int dl_task_check_affinity(struct task_struct *p, const struct cpu
}
#endif

+extern bool task_is_pi_boosted(const struct task_struct *p);
extern int yield_to(struct task_struct *p, bool preempt);
extern void set_user_nice(struct task_struct *p, long nice);
extern int task_prio(const struct task_struct *p);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c52c2eba7c739..132f06522efa0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8886,6 +8886,21 @@ static inline void preempt_dynamic_init(void) { }

#endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */

+/*
+ * task_is_pi_boosted - Check if task has been PI boosted.
+ * @p: Task to check.
+ *
+ * Return true if task is subject to priority inheritance.
+ */
+bool task_is_pi_boosted(const struct task_struct *p)
+{
+ int prio = p->prio;
+
+ if (!rt_prio(prio))
+ return false;
+ return prio != p->normal_prio;
+}
+
/**
* yield - yield the current processor to other threads.
*
--
2.40.1
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