From: Christian Loehle <christian.loehle@arm.com>
Date: Wed, 3 Sep 2025 21:23:11 +0000 (+0100)
Subject: sched_ext: deprecation warn for scx_bpf_cpu_rq()
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5c48d88fe004988ec508923dbdd00549e65f4055;p=thirdparty%2Fkernel%2Fstable.git

sched_ext: deprecation warn for scx_bpf_cpu_rq()

scx_bpf_cpu_rq() works on an unlocked rq which generally isn't safe.
For the common use-cases scx_bpf_locked_rq() and
scx_bpf_cpu_curr() work, so add a deprecation warning
to scx_bpf_cpu_rq() so it can eventually be removed.

Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 4bd9b491b376a..4160a4a7af67e 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6351,9 +6351,18 @@ __bpf_kfunc s32 scx_bpf_task_cpu(const struct task_struct *p)
  */
 __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu)
 {
+	struct scx_sched *sch = scx_root;
+
 	if (!kf_cpu_valid(cpu, NULL))
 		return NULL;
 
+	if (!sch->warned_deprecated_rq) {
+		printk_deferred(KERN_WARNING "sched_ext: %s() is deprecated; "
+				"use scx_bpf_locked_rq() when holding rq lock "
+				"or scx_bpf_cpu_curr() to read remote curr safely.\n", __func__);
+		sch->warned_deprecated_rq = true;
+	}
+
 	return cpu_rq(cpu);
 }
 
diff --git a/kernel/sched/ext_internal.h b/kernel/sched/ext_internal.h
index af4c054fb6f85..2e289931e567f 100644
--- a/kernel/sched/ext_internal.h
+++ b/kernel/sched/ext_internal.h
@@ -872,6 +872,7 @@ struct scx_sched {
 	struct scx_sched_pcpu __percpu *pcpu;
 
 	bool			warned_zero_slice;
+	bool			warned_deprecated_rq;
 
 	atomic_t		exit_kind;
 	struct scx_exit_info	*exit_info;