linux-kernel - [PATCH 5/4] sched_ext/tools: Add compat wrapper for scx_bpf_task_set_slice/dsq

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Message-ID: <aOVk0V9WigQq6Qc_@slm.duckdns.org>
Date: Tue, 7 Oct 2025 09:06:57 -1000
From: Tejun Heo <tj@...nel.org>
To: David Vernet <void@...ifault.com>, Andrea Righi <arighi@...dia.com>,
	Changwoo Min <changwoo@...lia.com>
Cc: linux-kernel@...r.kernel.org, sched-ext@...ts.linux.dev
Subject: [PATCH 5/4] sched_ext/tools: Add compat wrapper for
 scx_bpf_task_set_slice/dsq_vtime()

for sub-scheduler authority checks. Add compat wrappers which fall back to
direct p->scx field writes on older kernels.

Suggested-by: Andrea Righi <arighi@...dia.com>
Signed-off-by: Tejun Heo <tj@...nel.org>
---
 tools/sched_ext/include/scx/common.bpf.h |    2 --
 tools/sched_ext/include/scx/compat.bpf.h |   24 ++++++++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

--- a/tools/sched_ext/include/scx/common.bpf.h
+++ b/tools/sched_ext/include/scx/common.bpf.h
@@ -101,8 +101,6 @@ s32 scx_bpf_pick_any_cpu_node(const cpum
 s32 scx_bpf_pick_any_cpu(const cpumask_t *cpus_allowed, u64 flags) __ksym;
 bool scx_bpf_task_running(const struct task_struct *p) __ksym;
 s32 scx_bpf_task_cpu(const struct task_struct *p) __ksym;
-bool scx_bpf_task_set_slice(struct task_struct *p, u64 slice) __ksym __weak;
-bool scx_bpf_task_set_dsq_vtime(struct task_struct *p, u64 vtime) __ksym __weak;
 struct rq *scx_bpf_cpu_rq(s32 cpu) __ksym;
 struct rq *scx_bpf_locked_rq(void) __ksym;
 struct task_struct *scx_bpf_cpu_curr(s32 cpu) __ksym __weak;
--- a/tools/sched_ext/include/scx/compat.bpf.h
+++ b/tools/sched_ext/include/scx/compat.bpf.h
@@ -235,6 +235,30 @@ scx_bpf_dsq_insert(struct task_struct *p
 }
 
 /*
+ * v6.19: scx_bpf_task_set_slice() and scx_bpf_task_set_dsq_vtime() added to for
+ * sub-sched authority checks. Drop the wrappers and move the decls to
+ * common.bpf.h after v6.22.
+ */
+bool scx_bpf_task_set_slice___new(struct task_struct *p, u64 slice) __ksym __weak;
+bool scx_bpf_task_set_dsq_vtime___new(struct task_struct *p, u64 vtime) __ksym __weak;
+
+static inline void scx_bpf_task_set_slice(struct task_struct *p, u64 slice)
+{
+	if (bpf_ksym_exists(scx_bpf_task_set_slice___new))
+		scx_bpf_task_set_slice___new(p, slice);
+	else
+		p->scx.slice = slice;
+}
+
+static inline void scx_bpf_task_set_dsq_vtime(struct task_struct *p, u64 vtime)
+{
+	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+		scx_bpf_task_set_dsq_vtime___new(p, vtime);
+	else
+		p->scx.dsq_vtime = vtime;
+}
+
+/*
  * Define sched_ext_ops. This may be expanded to define multiple variants for
  * backward compatibility. See compat.h::SCX_OPS_LOAD/ATTACH().
  */