linux-kernel - [PATCH 3/6] sched_ext: Move scx_buildin_idle_enabled check to scx_bpf_select_cpu

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Message-ID: <20241009214411.681233-4-tj@kernel.org>
Date: Wed,  9 Oct 2024 11:40:59 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com
Cc: kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	sched-ext@...a.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 3/6] sched_ext: Move scx_buildin_idle_enabled check to scx_bpf_select_cpu_dfl()

Move the sanity check from the inner function scx_select_cpu_dfl() to the
exported kfunc scx_bpf_select_cpu_dfl(). This doesn't cause behavior
differences and will allow using scx_select_cpu_dfl() in bypass mode
regardless of scx_builtin_idle_enabled.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 7d2fa78ba0c9..1cae18000de1 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3062,11 +3062,6 @@ static s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 
 	*found = false;
 
-	if (!static_branch_likely(&scx_builtin_idle_enabled)) {
-		scx_ops_error("built-in idle tracking is disabled");
-		return prev_cpu;
-	}
-
 	/*
 	 * If WAKE_SYNC, the waker's local DSQ is empty, and the system is
 	 * under utilized, wake up @p to the local DSQ of the waker. Checking
@@ -5870,16 +5865,21 @@ __bpf_kfunc_start_defs();
 __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 				       u64 wake_flags, bool *is_idle)
 {
-	if (!scx_kf_allowed(SCX_KF_SELECT_CPU)) {
-		*is_idle = false;
-		return prev_cpu;
+	if (!static_branch_likely(&scx_builtin_idle_enabled)) {
+		scx_ops_error("built-in idle tracking is disabled");
+		goto prev_cpu;
 	}
+
+	if (!scx_kf_allowed(SCX_KF_SELECT_CPU))
+		goto prev_cpu;
+
 #ifdef CONFIG_SMP
 	return scx_select_cpu_dfl(p, prev_cpu, wake_flags, is_idle);
-#else
+#endif
+
+prev_cpu:
 	*is_idle = false;
 	return prev_cpu;
-#endif
 }
 
 __bpf_kfunc_end_defs();
-- 
2.46.2