[PATCH 1/5] sched_ext: Implement scx_rq_clock_update/stale()

[Changwoo Min <multics69@gmail.com>]

scx_rq_clock_update() and scx_rq_clock_stale() manage the status of an
rq clock. scx_rq_clock_update() keeps the rq clock in memory and its
status valid. scx_rq_clock_stale() invalidates the current rq clock
not to use the cached rq clock.

Signed-off-by: Changwoo Min <changwoo@igalia.com>
---
 kernel/sched/sched.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4d79804631e4..61efff790e24 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -754,6 +754,7 @@ enum scx_rq_flags {
 	SCX_RQ_BAL_PENDING	= 1 << 2, /* balance hasn't run yet */
 	SCX_RQ_BAL_KEEP		= 1 << 3, /* balance decided to keep current */
 	SCX_RQ_BYPASSING	= 1 << 4,
+	SCX_RQ_CLK_UPDATED	= 1 << 5, /* RQ clock is updated by the core */
 
 	SCX_RQ_IN_WAKEUP	= 1 << 16,
 	SCX_RQ_IN_BALANCE	= 1 << 17,
@@ -765,6 +766,7 @@ struct scx_rq {
 	struct list_head	ddsp_deferred_locals;	/* deferred ddsps from enq */
 	unsigned long		ops_qseq;
 	u64			extra_enq_flags;	/* see move_task_to_local_dsq() */
+	u64			clock;			/* cached per-rq clock -- see scx_bpf_clock_get_ns() */
 	u32			nr_running;
 	u32			flags;
 	u32			cpuperf_target;		/* [0, SCHED_CAPACITY_SCALE] */
@@ -1345,6 +1347,24 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 #define cpu_curr(cpu)		(cpu_rq(cpu)->curr)
 #define raw_rq()		raw_cpu_ptr(&runqueues)
 
+#ifdef CONFIG_SCHED_CLASS_EXT
+static inline void scx_rq_clock_update(struct rq *rq, u64 clock)
+{
+	rq->scx.clock = clock;
+	rq->scx.flags |= SCX_RQ_CLK_UPDATED;
+}
+
+static inline void scx_rq_clock_stale(struct rq *rq)
+{
+	rq->scx.flags &= ~SCX_RQ_CLK_UPDATED;
+}
+
+#else
+static inline void scx_rq_clock_update(struct rq *rq, u64 clock) {}
+static inline void scx_rq_clock_stale(struct rq *rq) {}
+
+#endif /* CONFIG_SCHED_CLASS_EXT */
+
 #ifdef CONFIG_SCHED_CORE
 static inline struct cpumask *sched_group_span(struct sched_group *sg);
 
-- 
2.47.0