kstep/linux/sync_wakeup.patch at master · kstep-dev/kstep · GitHub

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From cbd5455f3c9383c054fe55e820fc683d1b02cdbd Mon Sep 17 00:00:00 2001
From: Tingjia-0v0 <tjcao980311@gmail.com>
Date: Tue, 4 Nov 2025 03:42:15 -0600
Subject: [PATCH] aa3ee4f_fix

---
 kernel/sched/fair.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c798d2795243..76e3e016e2d8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1029,7 +1029,7 @@ static bool update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se)
 #include "pelt.h"
 #ifdef CONFIG_SMP

-static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
+static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu, bool sync);
 static unsigned long task_h_load(struct task_struct *p);
 static unsigned long capacity_of(int cpu);

@@ -7183,6 +7183,11 @@ static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 	return true;
 }

+static inline unsigned int cfs_h_nr_delayed(struct rq *rq)
+{
+	return (rq->cfs.h_nr_queued - rq->cfs.h_nr_runnable);
+}
+
 #ifdef CONFIG_SMP

 /* Working cpumask for: sched_balance_rq(), sched_balance_newidle(). */
@@ -7344,8 +7349,12 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
 	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
 		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;

-	if (sync && cpu_rq(this_cpu)->nr_running == 1)
-		return this_cpu;
+	if (sync) {
+		struct rq *rq = cpu_rq(this_cpu);
+
+		if ((rq->nr_running - cfs_h_nr_delayed(rq)) == 1)
+			return this_cpu;
+	}

 	if (available_idle_cpu(prev_cpu))
 		return prev_cpu;
@@ -7813,7 +7822,7 @@ static inline bool asym_fits_cpu(unsigned long util,
 /*
  * Try and locate an idle core/thread in the LLC cache domain.
  */
-static int select_idle_sibling(struct task_struct *p, int prev, int target)
+static int select_idle_sibling(struct task_struct *p, int prev, int target, bool sync)
 {
 	bool has_idle_core = false;
 	struct sched_domain *sd;
@@ -7840,6 +7849,8 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	    asym_fits_cpu(task_util, util_min, util_max, target))
 		return target;

+	if (sync && (cpu_rq(target)->nr_running - cfs_h_nr_delayed(cpu_rq(target))) == 1)
+		return target;
 	/*
 	 * If the previous CPU is cache affine and idle, don't be stupid:
 	 */
@@ -8621,7 +8632,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 		new_cpu = sched_balance_find_dst_cpu(sd, p, cpu, prev_cpu, sd_flag);
 	} else if (wake_flags & WF_TTWU) { /* XXX always ? */
 		/* Fast path */
-		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
+		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu, sync);
 	}
 	rcu_read_unlock();

--
2.43.0