[PATCH v31 9/9] sched: Distinguish proxy activations from wakeups

[John Stultz <jstultz@google.com>]

From: Andrea Righi <arighi@nvidia.com>

Sleeping-owner handling reactivates blocked waiters with wakeup enqueue
semantics so scheduling classes can restore their runnable accounting.
Unlike a normal wakeup, the waiter remains blocked and is only made
runnable to donate its scheduling context.

Add ENQUEUE_PROXY to identify this activation and set it alongside
ENQUEUE_WAKEUP. Consume the internal marker in sched_ext and suppress
SCX_ENQ_WAKEUP before invoking BPF so the activation can be handled as
a blocked proxy donor.

Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: John Stultz <jstultz@google.com>
---
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Zimuzo Ezeozue <zezeozue@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Metin Kaya <Metin.Kaya@arm.com>
Cc: Xuewen Yan <xuewen.yan94@gmail.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Andrea Righi <arighi@nvidia.com>
Cc: kuyo chang <kuyo.chang@mediatek.com>
Cc: hupu <hupu.gm@gmail.com>
Cc: kernel-team@android.com
---
 kernel/sched/core.c    | 2 +-
 kernel/sched/ext/ext.c | 8 ++++++++
 kernel/sched/sched.h   | 2 ++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d813a9c2f0c35..c54e9fedc9cd8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3900,7 +3900,7 @@ static void activate_blocked_waiters(struct rq *target_rq,
 {
 	struct list_head bal_head;
 	unsigned long flags;
-	int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
+	int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK | ENQUEUE_PROXY;
 
 	if (!sched_proxy_exec())
 		return;
diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index e3fa7b2fac9df..834c8b6dae6c9 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -2021,6 +2021,14 @@ static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int core_enq_
 	int sticky_cpu = p->scx.sticky_cpu;
 	u64 enq_flags = core_enq_flags | rq->scx.extra_enq_flags;
 
+	/*
+	 * Sleeping-owner activation uses wakeup semantics for the core
+	 * scheduling classes, but the donor remains blocked. Expose it to BPF
+	 * as a blocked-donor admission rather than a full wakeup.
+	 */
+	if (core_enq_flags & ENQUEUE_PROXY)
+		enq_flags &= ~(ENQUEUE_PROXY | SCX_ENQ_WAKEUP);
+
 	if (enq_flags & ENQUEUE_WAKEUP)
 		rq->scx.flags |= SCX_RQ_IN_WAKEUP;
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 56d9c09c485e6..e38988574cfa2 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2540,6 +2540,7 @@ extern const u32		sched_prio_to_wmult[40];
  * ENQUEUE_REPLENISH - CBS (replenish runtime and postpone deadline)
  * ENQUEUE_MIGRATED  - the task was migrated during wakeup
  * ENQUEUE_RQ_SELECTED - ->select_task_rq() was called
+ * ENQUEUE_PROXY     - activate a blocked donor behind a waking owner
  *
  * XXX SAVE/RESTORE in combination with CLASS doesn't really make sense, but
  * SCHED_DEADLINE seems to rely on this for now.
@@ -2571,6 +2572,7 @@ extern const u32		sched_prio_to_wmult[40];
 #define ENQUEUE_MIGRATED	0x00040000
 #define ENQUEUE_INITIAL		0x00080000
 #define ENQUEUE_RQ_SELECTED	0x00100000
+#define ENQUEUE_PROXY		0x00200000
 
 #define RETRY_TASK		((void *)-1UL)
 
-- 
2.55.0.229.g6434b31f56-goog