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Message-ID: <20250920005931.2753828-12-tj@kernel.org>
Date: Fri, 19 Sep 2025 14:58:34 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com,
arighi@...dia.com,
multics69@...il.com
Cc: linux-kernel@...r.kernel.org,
sched-ext@...ts.linux.dev,
memxor@...il.com,
bpf@...r.kernel.org,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 11/46] sched_ext: Drop kf_cpu_valid()
The intention behind kf_cpu_valid() was that when called from kfuncs,
kf_cpu_valid() would be able to implicitly determine the scx_sched instance
being operated on and thus wouldn't need @sch passed in explicitly. This
turned out to be unnecessarily complicated to implement and not have
justifiable practical benefits. Replace kf_cpu_valid() usages with
ops_cpu_valid() which takes explicit @sch.
Callers which don't have $sch available in the context are updated to read
$scx_root under RCU read lock, verify that it's not NULL and pass it in.
scx_bpf_cpu_rq() is restructured to use guard(rcu)() instead of explicit
rcu_read_[un]lock().
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/sched/ext.c | 67 ++++++++++++++++++++++++-----------------
kernel/sched/ext_idle.c | 12 +++++---
2 files changed, 48 insertions(+), 31 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 373146154829..56ca09f46d1e 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -736,23 +736,6 @@ static bool ops_cpu_valid(struct scx_sched *sch, s32 cpu, const char *where)
}
}
-/**
- * kf_cpu_valid - Verify a CPU number, to be used on kfunc input args
- * @cpu: cpu number which came from a BPF ops
- * @where: extra information reported on error
- *
- * The same as ops_cpu_valid() but @sch is implicit.
- */
-static bool kf_cpu_valid(u32 cpu, const char *where)
-{
- if (__cpu_valid(cpu)) {
- return true;
- } else {
- scx_kf_error("invalid CPU %d%s%s", cpu, where ? " " : "", where ?: "");
- return false;
- }
-}
-
/**
* ops_sanitize_err - Sanitize a -errno value
* @sch: scx_sched to error out on error
@@ -5815,7 +5798,7 @@ static void scx_kick_cpu(struct scx_sched *sch, s32 cpu, u64 flags)
struct rq *this_rq;
unsigned long irq_flags;
- if (!kf_cpu_valid(cpu, NULL))
+ if (!ops_cpu_valid(sch, cpu, NULL))
return;
local_irq_save(irq_flags);
@@ -6224,7 +6207,12 @@ __bpf_kfunc void scx_bpf_dump_bstr(char *fmt, unsigned long long *data,
*/
__bpf_kfunc u32 scx_bpf_cpuperf_cap(s32 cpu)
{
- if (kf_cpu_valid(cpu, NULL))
+ struct scx_sched *sch;
+
+ guard(rcu)();
+
+ sch = rcu_dereference(scx_root);
+ if (likely(sch) && ops_cpu_valid(sch, cpu, NULL))
return arch_scale_cpu_capacity(cpu);
else
return SCX_CPUPERF_ONE;
@@ -6246,7 +6234,12 @@ __bpf_kfunc u32 scx_bpf_cpuperf_cap(s32 cpu)
*/
__bpf_kfunc u32 scx_bpf_cpuperf_cur(s32 cpu)
{
- if (kf_cpu_valid(cpu, NULL))
+ struct scx_sched *sch;
+
+ guard(rcu)();
+
+ sch = rcu_dereference(scx_root);
+ if (likely(sch) && ops_cpu_valid(sch, cpu, NULL))
return arch_scale_freq_capacity(cpu);
else
return SCX_CPUPERF_ONE;
@@ -6268,12 +6261,20 @@ __bpf_kfunc u32 scx_bpf_cpuperf_cur(s32 cpu)
*/
__bpf_kfunc void scx_bpf_cpuperf_set(s32 cpu, u32 perf)
{
+ struct scx_sched *sch;
+
+ guard(rcu)();
+
+ sch = rcu_dereference(sch);
+ if (unlikely(!sch))
+ return;
+
if (unlikely(perf > SCX_CPUPERF_ONE)) {
scx_kf_error("Invalid cpuperf target %u for CPU %d", perf, cpu);
return;
}
- if (kf_cpu_valid(cpu, NULL)) {
+ if (ops_cpu_valid(sch, cpu, NULL)) {
struct rq *rq = cpu_rq(cpu), *locked_rq = scx_locked_rq();
struct rq_flags rf;
@@ -6379,18 +6380,21 @@ __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu)
{
struct scx_sched *sch;
- if (!kf_cpu_valid(cpu, NULL))
- return NULL;
+ guard(rcu)();
- rcu_read_lock();
sch = rcu_dereference(scx_root);
- if (likely(sch) && !sch->warned_deprecated_rq) {
+ if (unlikely(!sch))
+ return NULL;
+
+ if (!ops_cpu_valid(sch, 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;
}
- rcu_read_unlock();
return cpu_rq(cpu);
}
@@ -6425,8 +6429,17 @@ __bpf_kfunc struct rq *scx_bpf_locked_rq(void)
*/
__bpf_kfunc struct task_struct *scx_bpf_cpu_curr(s32 cpu)
{
- if (!kf_cpu_valid(cpu, NULL))
+ struct scx_sched *sch;
+
+ guard(rcu)();
+
+ sch = rcu_dereference(scx_root);
+ if (unlikely(!sch))
return NULL;
+
+ if (!ops_cpu_valid(sch, cpu, NULL))
+ return NULL;
+
return rcu_dereference(cpu_rq(cpu)->curr);
}
diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
index 6e2504ae7357..a576ec10522e 100644
--- a/kernel/sched/ext_idle.c
+++ b/kernel/sched/ext_idle.c
@@ -864,7 +864,7 @@ static s32 select_cpu_from_kfunc(struct scx_sched *sch, struct task_struct *p,
struct rq_flags rf;
s32 cpu;
- if (!kf_cpu_valid(prev_cpu, NULL))
+ if (!ops_cpu_valid(sch, prev_cpu, NULL))
return -EINVAL;
if (!check_builtin_idle_enabled(sch))
@@ -923,9 +923,13 @@ static s32 select_cpu_from_kfunc(struct scx_sched *sch, struct task_struct *p,
*/
__bpf_kfunc int scx_bpf_cpu_node(s32 cpu)
{
- if (!kf_cpu_valid(cpu, NULL))
- return NUMA_NO_NODE;
+ struct scx_sched *sch;
+
+ guard(rcu)();
+ sch = rcu_dereference(scx_root);
+ if (unlikely(!sch) || !ops_cpu_valid(sch, cpu, NULL))
+ return NUMA_NO_NODE;
return cpu_to_node(cpu);
}
@@ -1154,7 +1158,7 @@ __bpf_kfunc bool scx_bpf_test_and_clear_cpu_idle(s32 cpu)
if (!check_builtin_idle_enabled(sch))
return false;
- if (!kf_cpu_valid(cpu, NULL))
+ if (!ops_cpu_valid(sch, cpu, NULL))
return false;
return scx_idle_test_and_clear_cpu(cpu);
--
2.51.0
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