From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Cheng-Yang Chou <yphbchou0911@gmail.com>,
	Andrea Righi <arighi@nvidia.com>,
	Tejun Heo <tj@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18 0657/1250] sched_ext: Update demo schedulers and selftests to use scx_bpf_task_set_dsq_vtime()
Date: Thu, 17 Sep 2026 16:07:32 +0100
Message-ID: <20260917151609.702092147@linuxfoundation.org>
In-Reply-To: <20260917151551.901433442@linuxfoundation.org>
References: <20260917151551.901433442@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Cheng-Yang Chou <yphbchou0911@gmail.com>

[ Upstream commit 6712c4fefca0422851b71d1a58a32ea03f69310f ]

Direct writes to p->scx.dsq_vtime are deprecated in favor of
scx_bpf_task_set_dsq_vtime(). Update scx_simple, scx_flatcg, and
select_cpu_vtime selftest to use the new kfunc with
scale_by_task_weight_inverse().

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Stable-dep-of: b6ee92d7f7f0 ("sched_ext: Fix vtime delta loss in scx_flatcg cgroup migration")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/sched_ext/scx_flatcg.bpf.c                     | 12 +++++++-----
 tools/sched_ext/scx_simple.bpf.c                     |  6 ++++--
 .../selftests/sched_ext/select_cpu_vtime.bpf.c       |  6 ++++--
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/tools/sched_ext/scx_flatcg.bpf.c b/tools/sched_ext/scx_flatcg.bpf.c
index 2e757f3b13530..7d2c5ab114242 100644
--- a/tools/sched_ext/scx_flatcg.bpf.c
+++ b/tools/sched_ext/scx_flatcg.bpf.c
@@ -551,9 +551,11 @@ void BPF_STRUCT_OPS(fcg_stopping, struct task_struct *p, bool runnable)
 	 * too much, determine the execution time by taking explicit timestamps
 	 * instead of depending on @p->scx.slice.
 	 */
-	if (!fifo_sched)
-		p->scx.dsq_vtime +=
-			(SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+	if (!fifo_sched) {
+		u64 delta = scale_by_task_weight_inverse(p, SCX_SLICE_DFL - p->scx.slice);
+
+		scx_bpf_task_set_dsq_vtime(p, p->scx.dsq_vtime + delta);
+	}
 
 	taskc = bpf_task_storage_get(&task_ctx, p, 0, 0);
 	if (!taskc) {
@@ -831,7 +833,7 @@ s32 BPF_STRUCT_OPS(fcg_init_task, struct task_struct *p,
 	if (!(cgc = find_cgrp_ctx(args->cgroup)))
 		return -ENOENT;
 
-	p->scx.dsq_vtime = cgc->tvtime_now;
+	scx_bpf_task_set_dsq_vtime(p, cgc->tvtime_now);
 
 	return 0;
 }
@@ -931,7 +933,7 @@ void BPF_STRUCT_OPS(fcg_cgroup_move, struct task_struct *p,
 		return;
 
 	delta = time_delta(p->scx.dsq_vtime, from_cgc->tvtime_now);
-	p->scx.dsq_vtime = to_cgc->tvtime_now + delta;
+	scx_bpf_task_set_dsq_vtime(p, to_cgc->tvtime_now + delta);
 }
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(fcg_init)
diff --git a/tools/sched_ext/scx_simple.bpf.c b/tools/sched_ext/scx_simple.bpf.c
index e6de99dba7db6..ab2a85316de39 100644
--- a/tools/sched_ext/scx_simple.bpf.c
+++ b/tools/sched_ext/scx_simple.bpf.c
@@ -121,12 +121,14 @@ void BPF_STRUCT_OPS(simple_stopping, struct task_struct *p, bool runnable)
 	 * too much, determine the execution time by taking explicit timestamps
 	 * instead of depending on @p->scx.slice.
 	 */
-	p->scx.dsq_vtime += (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+	u64 delta = scale_by_task_weight_inverse(p, SCX_SLICE_DFL - p->scx.slice);
+
+	scx_bpf_task_set_dsq_vtime(p, p->scx.dsq_vtime + delta);
 }
 
 void BPF_STRUCT_OPS(simple_enable, struct task_struct *p)
 {
-	p->scx.dsq_vtime = vtime_now;
+	scx_bpf_task_set_dsq_vtime(p, vtime_now);
 }
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(simple_init)
diff --git a/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c b/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
index bfcb96cd4954b..aad8de51723e9 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
@@ -66,12 +66,14 @@ void BPF_STRUCT_OPS(select_cpu_vtime_running, struct task_struct *p)
 void BPF_STRUCT_OPS(select_cpu_vtime_stopping, struct task_struct *p,
 		    bool runnable)
 {
-	p->scx.dsq_vtime += (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+	u64 delta = scale_by_task_weight_inverse(p, SCX_SLICE_DFL - p->scx.slice);
+
+	scx_bpf_task_set_dsq_vtime(p, p->scx.dsq_vtime + delta);
 }
 
 void BPF_STRUCT_OPS(select_cpu_vtime_enable, struct task_struct *p)
 {
-	p->scx.dsq_vtime = vtime_now;
+	scx_bpf_task_set_dsq_vtime(p, vtime_now);
 }
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(select_cpu_vtime_init)
-- 
2.53.0