[PATCHSET sched_ext/scx-misc-a] sched_ext: Add @sch parameter in preparation for multi-sched support

[PATCHSET sched_ext/scx-misc-a] sched_ext: Add @sch parameter in preparation for multi-sched support

[Tejun Heo]

This patchset systematically adds the @sch parameter to various sched_ext
functions in preparation for multiple scheduler support. This part is
needed regardless of how the rest of the multiple scheduler patchset
develops. The changes also remove a bunch of naked scx_root dereferences
that trigger sparse warnings. The changes are mostly mechanical parameter
additions without functional changes.

The patches are based on sched_ext/for-6.18 (ac6772e8bcda) +
"sched_ext: misc cleanups and improvements"
(http://lkml.kernel.org/r/20250922013246.275031-1-tj@kernel.org).

 1 sched_ext: Separate out scx_kick_cpu() and add @sch to it
 2 sched_ext: Add the @sch parameter to __bstr_format()
 3 sched_ext: Add the @sch parameter to ext_idle helpers
 4 sched_ext: Drop kf_cpu_valid()
 5 sched_ext: Add the @sch parameter to scx_dsq_insert_preamble/commit()
 6 sched_ext: Drop scx_kf_exit() and scx_kf_error()
 7 sched_ext: Misc updates around scx_sched instance pointer

The following git tree also contains the patchset:

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-sub-sched-misc-prep

 kernel/sched/ext.c      | 355 ++++++++++++++++++++++++++++++------------------
 kernel/sched/ext_idle.c | 146 ++++++++++++++++----
 2 files changed, 340 insertions(+), 161 deletions(-)

--
tejun

[PATCH 1/7] sched_ext: Separate out scx_kick_cpu() and add @sch to it

[Tejun Heo]

In preparation for multiple scheduler support, separate out scx_kick_cpu()
from scx_bpf_kick_cpu() and add the @sch parameter to it. scx_bpf_kick_cpu()
now acquires an RCU read lock, reads $scx_root, and calls scx_kick_cpu()
with it if non-NULL. The passed in @sch parameter is not used yet.

Internal uses of scx_bpf_kick_cpu() are converted to scx_kick_cpu(). Where
$sch is available, it's used. In the pick_task_scx() path where no
associated scheduler can be identified, $scx_root is used directly. Note
that $scx_root cannot be NULL in this case.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c | 43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index d131e98156ac..560ac5a575bd 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -136,7 +136,7 @@ static struct kset *scx_kset;
 #include <trace/events/sched_ext.h>
 
 static void process_ddsp_deferred_locals(struct rq *rq);
-static void scx_bpf_kick_cpu(s32 cpu, u64 flags);
+static void scx_kick_cpu(struct scx_sched *sch, s32 cpu, u64 flags);
 static void scx_vexit(struct scx_sched *sch, enum scx_exit_kind kind,
 		      s64 exit_code, const char *fmt, va_list args);
 
@@ -2125,10 +2125,10 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
 		 * balance(), we want to complete this scheduling cycle and then
 		 * start a new one. IOW, we want to call resched_curr() on the
 		 * next, most likely idle, task, not the current one. Use
-		 * scx_bpf_kick_cpu() for deferred kicking.
+		 * scx_kick_cpu() for deferred kicking.
 		 */
 		if (unlikely(!--nr_loops)) {
-			scx_bpf_kick_cpu(cpu_of(rq), 0);
+			scx_kick_cpu(sch, cpu_of(rq), 0);
 			break;
 		}
 	} while (dspc->nr_tasks);
@@ -2417,7 +2417,8 @@ static struct task_struct *pick_task_scx(struct rq *rq)
 		p = first_local_task(rq);
 		if (!p) {
 			if (kick_idle)
-				scx_bpf_kick_cpu(cpu_of(rq), SCX_KICK_IDLE);
+				scx_kick_cpu(rcu_dereference_sched(scx_root),
+					     cpu_of(rq), SCX_KICK_IDLE);
 			return NULL;
 		}
 
@@ -3721,7 +3722,7 @@ static void scx_clear_softlockup(void)
  *
  * - pick_next_task() suppresses zero slice warning.
  *
- * - scx_bpf_kick_cpu() is disabled to avoid irq_work malfunction during PM
+ * - scx_kick_cpu() is disabled to avoid irq_work malfunction during PM
  *   operations.
  *
  * - scx_prio_less() reverts to the default core_sched_at order.
@@ -5809,17 +5810,7 @@ static const struct btf_kfunc_id_set scx_kfunc_set_unlocked = {
 
 __bpf_kfunc_start_defs();
 
-/**
- * scx_bpf_kick_cpu - Trigger reschedule on a CPU
- * @cpu: cpu to kick
- * @flags: %SCX_KICK_* flags
- *
- * Kick @cpu into rescheduling. This can be used to wake up an idle CPU or
- * trigger rescheduling on a busy CPU. This can be called from any online
- * scx_ops operation and the actual kicking is performed asynchronously through
- * an irq work.
- */
-__bpf_kfunc void scx_bpf_kick_cpu(s32 cpu, u64 flags)
+static void scx_kick_cpu(struct scx_sched *sch, s32 cpu, u64 flags)
 {
 	struct rq *this_rq;
 	unsigned long irq_flags;
@@ -5872,6 +5863,26 @@ __bpf_kfunc void scx_bpf_kick_cpu(s32 cpu, u64 flags)
 	local_irq_restore(irq_flags);
 }
 
+/**
+ * scx_bpf_kick_cpu - Trigger reschedule on a CPU
+ * @cpu: cpu to kick
+ * @flags: %SCX_KICK_* flags
+ *
+ * Kick @cpu into rescheduling. This can be used to wake up an idle CPU or
+ * trigger rescheduling on a busy CPU. This can be called from any online
+ * scx_ops operation and the actual kicking is performed asynchronously through
+ * an irq work.
+ */
+__bpf_kfunc void scx_bpf_kick_cpu(s32 cpu, u64 flags)
+{
+	struct scx_sched *sch;
+
+	guard(rcu)();
+	sch = rcu_dereference(scx_root);
+	if (likely(sch))
+		scx_kick_cpu(sch, cpu, flags);
+}
+
 /**
  * scx_bpf_dsq_nr_queued - Return the number of queued tasks
  * @dsq_id: id of the DSQ
-- 
2.51.0

[PATCH 2/7] sched_ext: Add the @sch parameter to __bstr_format()

[Tejun Heo]

In preparation for multiple scheduler support, add the @sch parameter to
__bstr_format() and update the callers to read $scx_root, verify that it's
not NULL and pass it in. The passed in @sch parameter is not used yet.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 560ac5a575bd..373146154829 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6063,8 +6063,9 @@ __bpf_kfunc void bpf_iter_scx_dsq_destroy(struct bpf_iter_scx_dsq *it)
 
 __bpf_kfunc_end_defs();
 
-static s32 __bstr_format(u64 *data_buf, char *line_buf, size_t line_size,
-			 char *fmt, unsigned long long *data, u32 data__sz)
+static s32 __bstr_format(struct scx_sched *sch, u64 *data_buf, char *line_buf,
+			 size_t line_size, char *fmt, unsigned long long *data,
+			 u32 data__sz)
 {
 	struct bpf_bprintf_data bprintf_data = { .get_bin_args = true };
 	s32 ret;
@@ -6099,10 +6100,10 @@ static s32 __bstr_format(u64 *data_buf, char *line_buf, size_t line_size,
 	return ret;
 }
 
-static s32 bstr_format(struct scx_bstr_buf *buf,
+static s32 bstr_format(struct scx_sched *sch, struct scx_bstr_buf *buf,
 		       char *fmt, unsigned long long *data, u32 data__sz)
 {
-	return __bstr_format(buf->data, buf->line, sizeof(buf->line),
+	return __bstr_format(sch, buf->data, buf->line, sizeof(buf->line),
 			     fmt, data, data__sz);
 }
 
@@ -6121,10 +6122,13 @@ __bpf_kfunc_start_defs();
 __bpf_kfunc void scx_bpf_exit_bstr(s64 exit_code, char *fmt,
 				   unsigned long long *data, u32 data__sz)
 {
+	struct scx_sched *sch;
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&scx_exit_bstr_buf_lock, flags);
-	if (bstr_format(&scx_exit_bstr_buf, fmt, data, data__sz) >= 0)
+	sch = rcu_dereference_bh(scx_root);
+	if (likely(sch) &&
+	    bstr_format(sch, &scx_exit_bstr_buf, fmt, data, data__sz) >= 0)
 		scx_kf_exit(SCX_EXIT_UNREG_BPF, exit_code, "%s", scx_exit_bstr_buf.line);
 	raw_spin_unlock_irqrestore(&scx_exit_bstr_buf_lock, flags);
 }
@@ -6141,10 +6145,13 @@ __bpf_kfunc void scx_bpf_exit_bstr(s64 exit_code, char *fmt,
 __bpf_kfunc void scx_bpf_error_bstr(char *fmt, unsigned long long *data,
 				    u32 data__sz)
 {
+	struct scx_sched *sch;
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&scx_exit_bstr_buf_lock, flags);
-	if (bstr_format(&scx_exit_bstr_buf, fmt, data, data__sz) >= 0)
+	sch = rcu_dereference_bh(scx_root);
+	if (likely(sch) &&
+	    bstr_format(sch, &scx_exit_bstr_buf, fmt, data, data__sz) >= 0)
 		scx_kf_exit(SCX_EXIT_ERROR_BPF, 0, "%s", scx_exit_bstr_buf.line);
 	raw_spin_unlock_irqrestore(&scx_exit_bstr_buf_lock, flags);
 }
@@ -6164,17 +6171,24 @@ __bpf_kfunc void scx_bpf_error_bstr(char *fmt, unsigned long long *data,
 __bpf_kfunc void scx_bpf_dump_bstr(char *fmt, unsigned long long *data,
 				   u32 data__sz)
 {
+	struct scx_sched *sch;
 	struct scx_dump_data *dd = &scx_dump_data;
 	struct scx_bstr_buf *buf = &dd->buf;
 	s32 ret;
 
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return;
+
 	if (raw_smp_processor_id() != dd->cpu) {
 		scx_kf_error("scx_bpf_dump() must only be called from ops.dump() and friends");
 		return;
 	}
 
 	/* append the formatted string to the line buf */
-	ret = __bstr_format(buf->data, buf->line + dd->cursor,
+	ret = __bstr_format(sch, buf->data, buf->line + dd->cursor,
 			    sizeof(buf->line) - dd->cursor, fmt, data, data__sz);
 	if (ret < 0) {
 		dump_line(dd->s, "%s[!] (\"%s\", %p, %u) failed to format (%d)",
-- 
2.51.0

[PATCH 3/7] sched_ext: Add the @sch parameter to ext_idle helpers

[Tejun Heo]

In preparation for multiple scheduler support, add the @sch parameter to
validate_node(), check_builtin_idle_enabled() and select_cpu_from_kfunc(),
and update their callers to read $scx_root, verify that it's not NULL and
pass it in. The passed in @sch parameter is not used yet.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext_idle.c | 109 ++++++++++++++++++++++++++++++++++------
 1 file changed, 94 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
index 7174e1c1a392..6e2504ae7357 100644
--- a/kernel/sched/ext_idle.c
+++ b/kernel/sched/ext_idle.c
@@ -819,7 +819,7 @@ void scx_idle_disable(void)
  * Helpers that can be called from the BPF scheduler.
  */
 
-static int validate_node(int node)
+static int validate_node(struct scx_sched *sch, int node)
 {
 	if (!static_branch_likely(&scx_builtin_idle_per_node)) {
 		scx_kf_error("per-node idle tracking is disabled");
@@ -847,7 +847,7 @@ static int validate_node(int node)
 
 __bpf_kfunc_start_defs();
 
-static bool check_builtin_idle_enabled(void)
+static bool check_builtin_idle_enabled(struct scx_sched *sch)
 {
 	if (static_branch_likely(&scx_builtin_idle_enabled))
 		return true;
@@ -856,7 +856,8 @@ static bool check_builtin_idle_enabled(void)
 	return false;
 }
 
-static s32 select_cpu_from_kfunc(struct task_struct *p, s32 prev_cpu, u64 wake_flags,
+static s32 select_cpu_from_kfunc(struct scx_sched *sch, struct task_struct *p,
+				 s32 prev_cpu, u64 wake_flags,
 				 const struct cpumask *allowed, u64 flags)
 {
 	struct rq *rq;
@@ -866,7 +867,7 @@ static s32 select_cpu_from_kfunc(struct task_struct *p, s32 prev_cpu, u64 wake_f
 	if (!kf_cpu_valid(prev_cpu, NULL))
 		return -EINVAL;
 
-	if (!check_builtin_idle_enabled())
+	if (!check_builtin_idle_enabled(sch))
 		return -EBUSY;
 
 	/*
@@ -946,15 +947,21 @@ __bpf_kfunc int scx_bpf_cpu_node(s32 cpu)
 __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 				       u64 wake_flags, bool *is_idle)
 {
+	struct scx_sched *sch;
 	s32 cpu;
 
-	cpu = select_cpu_from_kfunc(p, prev_cpu, wake_flags, NULL, 0);
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return -ENODEV;
+
+	cpu = select_cpu_from_kfunc(sch, p, prev_cpu, wake_flags, NULL, 0);
 	if (cpu >= 0) {
 		*is_idle = true;
 		return cpu;
 	}
 	*is_idle = false;
-
 	return prev_cpu;
 }
 
@@ -981,7 +988,16 @@ __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 __bpf_kfunc s32 scx_bpf_select_cpu_and(struct task_struct *p, s32 prev_cpu, u64 wake_flags,
 				       const struct cpumask *cpus_allowed, u64 flags)
 {
-	return select_cpu_from_kfunc(p, prev_cpu, wake_flags, cpus_allowed, flags);
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return -ENODEV;
+
+	return select_cpu_from_kfunc(sch, p, prev_cpu, wake_flags,
+				     cpus_allowed, flags);
 }
 
 /**
@@ -995,7 +1011,15 @@ __bpf_kfunc s32 scx_bpf_select_cpu_and(struct task_struct *p, s32 prev_cpu, u64
  */
 __bpf_kfunc const struct cpumask *scx_bpf_get_idle_cpumask_node(int node)
 {
-	node = validate_node(node);
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return cpu_none_mask;
+
+	node = validate_node(sch, node);
 	if (node < 0)
 		return cpu_none_mask;
 
@@ -1011,12 +1035,20 @@ __bpf_kfunc const struct cpumask *scx_bpf_get_idle_cpumask_node(int node)
  */
 __bpf_kfunc const struct cpumask *scx_bpf_get_idle_cpumask(void)
 {
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return cpu_none_mask;
+
 	if (static_branch_unlikely(&scx_builtin_idle_per_node)) {
 		scx_kf_error("SCX_OPS_BUILTIN_IDLE_PER_NODE enabled");
 		return cpu_none_mask;
 	}
 
-	if (!check_builtin_idle_enabled())
+	if (!check_builtin_idle_enabled(sch))
 		return cpu_none_mask;
 
 	return idle_cpumask(NUMA_NO_NODE)->cpu;
@@ -1034,7 +1066,15 @@ __bpf_kfunc const struct cpumask *scx_bpf_get_idle_cpumask(void)
  */
 __bpf_kfunc const struct cpumask *scx_bpf_get_idle_smtmask_node(int node)
 {
-	node = validate_node(node);
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return cpu_none_mask;
+
+	node = validate_node(sch, node);
 	if (node < 0)
 		return cpu_none_mask;
 
@@ -1054,12 +1094,20 @@ __bpf_kfunc const struct cpumask *scx_bpf_get_idle_smtmask_node(int node)
  */
 __bpf_kfunc const struct cpumask *scx_bpf_get_idle_smtmask(void)
 {
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return cpu_none_mask;
+
 	if (static_branch_unlikely(&scx_builtin_idle_per_node)) {
 		scx_kf_error("SCX_OPS_BUILTIN_IDLE_PER_NODE enabled");
 		return cpu_none_mask;
 	}
 
-	if (!check_builtin_idle_enabled())
+	if (!check_builtin_idle_enabled(sch))
 		return cpu_none_mask;
 
 	if (sched_smt_active())
@@ -1095,7 +1143,15 @@ __bpf_kfunc void scx_bpf_put_idle_cpumask(const struct cpumask *idle_mask)
  */
 __bpf_kfunc bool scx_bpf_test_and_clear_cpu_idle(s32 cpu)
 {
-	if (!check_builtin_idle_enabled())
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return false;
+
+	if (!check_builtin_idle_enabled(sch))
 		return false;
 
 	if (!kf_cpu_valid(cpu, NULL))
@@ -1126,7 +1182,15 @@ __bpf_kfunc bool scx_bpf_test_and_clear_cpu_idle(s32 cpu)
 __bpf_kfunc s32 scx_bpf_pick_idle_cpu_node(const struct cpumask *cpus_allowed,
 					   int node, u64 flags)
 {
-	node = validate_node(node);
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return -ENODEV;
+
+	node = validate_node(sch, node);
 	if (node < 0)
 		return node;
 
@@ -1158,12 +1222,20 @@ __bpf_kfunc s32 scx_bpf_pick_idle_cpu_node(const struct cpumask *cpus_allowed,
 __bpf_kfunc s32 scx_bpf_pick_idle_cpu(const struct cpumask *cpus_allowed,
 				      u64 flags)
 {
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return -ENODEV;
+
 	if (static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) {
 		scx_kf_error("per-node idle tracking is enabled");
 		return -EBUSY;
 	}
 
-	if (!check_builtin_idle_enabled())
+	if (!check_builtin_idle_enabled(sch))
 		return -EBUSY;
 
 	return scx_pick_idle_cpu(cpus_allowed, NUMA_NO_NODE, flags);
@@ -1193,9 +1265,16 @@ __bpf_kfunc s32 scx_bpf_pick_idle_cpu(const struct cpumask *cpus_allowed,
 __bpf_kfunc s32 scx_bpf_pick_any_cpu_node(const struct cpumask *cpus_allowed,
 					  int node, u64 flags)
 {
+	struct scx_sched *sch;
 	s32 cpu;
 
-	node = validate_node(node);
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return -ENODEV;
+
+	node = validate_node(sch, node);
 	if (node < 0)
 		return node;
 
-- 
2.51.0

[PATCH 4/7] sched_ext: Drop kf_cpu_valid()

[Tejun Heo]

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@kernel.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

[PATCH 5/7] sched_ext: Add the @sch parameter to scx_dsq_insert_preamble/commit()

[Tejun Heo]

In preparation for multiple scheduler support, add the @sch parameter to
scx_dsq_insert_preamble/commit() and update the callers to read $scx_root
and pass it in. The passed in @sch parameter is not used yet.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 56ca09f46d1e..1455f8c56d5c 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -5240,7 +5240,8 @@ void __init init_sched_ext_class(void)
 /********************************************************************************
  * Helpers that can be called from the BPF scheduler.
  */
-static bool scx_dsq_insert_preamble(struct task_struct *p, u64 enq_flags)
+static bool scx_dsq_insert_preamble(struct scx_sched *sch, struct task_struct *p,
+				    u64 enq_flags)
 {
 	if (!scx_kf_allowed(SCX_KF_ENQUEUE | SCX_KF_DISPATCH))
 		return false;
@@ -5260,8 +5261,8 @@ static bool scx_dsq_insert_preamble(struct task_struct *p, u64 enq_flags)
 	return true;
 }
 
-static void scx_dsq_insert_commit(struct task_struct *p, u64 dsq_id,
-				  u64 enq_flags)
+static void scx_dsq_insert_commit(struct scx_sched *sch, struct task_struct *p,
+				  u64 dsq_id, u64 enq_flags)
 {
 	struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx);
 	struct task_struct *ddsp_task;
@@ -5325,7 +5326,14 @@ __bpf_kfunc_start_defs();
 __bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice,
 				    u64 enq_flags)
 {
-	if (!scx_dsq_insert_preamble(p, enq_flags))
+	struct scx_sched *sch;
+
+	guard(rcu)();
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return;
+
+	if (!scx_dsq_insert_preamble(sch, p, enq_flags))
 		return;
 
 	if (slice)
@@ -5333,7 +5341,7 @@ __bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice
 	else
 		p->scx.slice = p->scx.slice ?: 1;
 
-	scx_dsq_insert_commit(p, dsq_id, enq_flags);
+	scx_dsq_insert_commit(sch, p, dsq_id, enq_flags);
 }
 
 /**
@@ -5360,7 +5368,14 @@ __bpf_kfunc void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice
 __bpf_kfunc void scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id,
 					  u64 slice, u64 vtime, u64 enq_flags)
 {
-	if (!scx_dsq_insert_preamble(p, enq_flags))
+	struct scx_sched *sch;
+
+	guard(rcu)();
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return;
+
+	if (!scx_dsq_insert_preamble(sch, p, enq_flags))
 		return;
 
 	if (slice)
@@ -5370,7 +5385,7 @@ __bpf_kfunc void scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id,
 
 	p->scx.dsq_vtime = vtime;
 
-	scx_dsq_insert_commit(p, dsq_id, enq_flags | SCX_ENQ_DSQ_PRIQ);
+	scx_dsq_insert_commit(sch, p, dsq_id, enq_flags | SCX_ENQ_DSQ_PRIQ);
 }
 
 __bpf_kfunc_end_defs();
-- 
2.51.0

[PATCH 6/7] sched_ext: Drop scx_kf_exit() and scx_kf_error()

[Tejun Heo]

The intention behind scx_kf_exit/error() was that when called from kfuncs,
scx_kf_exit/error() would be able to implicitly determine the scx_sched
instance being operated on and thus wouldn't need the @sch parameter passed
in explicitly. This turned out to be unnecessarily complicated to implement
and not have enough practical benefits. Replace scx_kf_exit/error() usages
with scx_exit/error() which take an explicit @sch parameter.

- Add the @sch parameter to scx_kf_allowed(), scx_kf_allowed_on_arg_tasks,
  mark_direct_dispatch() and other intermediate functions transitively.

- In callers that don't already have @sch available, grab RCU, read
  $scx_root, verify it's not NULL and use it.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c      | 126 +++++++++++++++++++++++-----------------
 kernel/sched/ext_idle.c |  25 +++++---
 2 files changed, 88 insertions(+), 63 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 1455f8c56d5c..0c99a55f199b 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -151,24 +151,7 @@ static __printf(4, 5) void scx_exit(struct scx_sched *sch,
 	va_end(args);
 }
 
-static __printf(3, 4) void scx_kf_exit(enum scx_exit_kind kind, s64 exit_code,
-				       const char *fmt, ...)
-{
-	struct scx_sched *sch;
-	va_list args;
-
-	rcu_read_lock();
-	sch = rcu_dereference(scx_root);
-	if (sch) {
-		va_start(args, fmt);
-		scx_vexit(sch, kind, exit_code, fmt, args);
-		va_end(args);
-	}
-	rcu_read_unlock();
-}
-
 #define scx_error(sch, fmt, args...)	scx_exit((sch), SCX_EXIT_ERROR, 0, fmt, ##args)
-#define scx_kf_error(fmt, args...)	scx_kf_exit(SCX_EXIT_ERROR, 0, fmt, ##args)
 
 #define SCX_HAS_OP(sch, op)	test_bit(SCX_OP_IDX(op), (sch)->has_op)
 
@@ -329,11 +312,11 @@ do {										\
 })
 
 /* @mask is constant, always inline to cull unnecessary branches */
-static __always_inline bool scx_kf_allowed(u32 mask)
+static __always_inline bool scx_kf_allowed(struct scx_sched *sch, u32 mask)
 {
 	if (unlikely(!(current->scx.kf_mask & mask))) {
-		scx_kf_error("kfunc with mask 0x%x called from an operation only allowing 0x%x",
-			     mask, current->scx.kf_mask);
+		scx_error(sch, "kfunc with mask 0x%x called from an operation only allowing 0x%x",
+			  mask, current->scx.kf_mask);
 		return false;
 	}
 
@@ -346,13 +329,13 @@ static __always_inline bool scx_kf_allowed(u32 mask)
 	 */
 	if (unlikely(highest_bit(mask) == SCX_KF_CPU_RELEASE &&
 		     (current->scx.kf_mask & higher_bits(SCX_KF_CPU_RELEASE)))) {
-		scx_kf_error("cpu_release kfunc called from a nested operation");
+		scx_error(sch, "cpu_release kfunc called from a nested operation");
 		return false;
 	}
 
 	if (unlikely(highest_bit(mask) == SCX_KF_DISPATCH &&
 		     (current->scx.kf_mask & higher_bits(SCX_KF_DISPATCH)))) {
-		scx_kf_error("dispatch kfunc called from a nested operation");
+		scx_error(sch, "dispatch kfunc called from a nested operation");
 		return false;
 	}
 
@@ -360,15 +343,16 @@ static __always_inline bool scx_kf_allowed(u32 mask)
 }
 
 /* see SCX_CALL_OP_TASK() */
-static __always_inline bool scx_kf_allowed_on_arg_tasks(u32 mask,
+static __always_inline bool scx_kf_allowed_on_arg_tasks(struct scx_sched *sch,
+							u32 mask,
 							struct task_struct *p)
 {
-	if (!scx_kf_allowed(mask))
+	if (!scx_kf_allowed(sch, mask))
 		return false;
 
 	if (unlikely((p != current->scx.kf_tasks[0] &&
 		      p != current->scx.kf_tasks[1]))) {
-		scx_kf_error("called on a task not being operated on");
+		scx_error(sch, "called on a task not being operated on");
 		return false;
 	}
 
@@ -1115,7 +1099,8 @@ static struct scx_dispatch_q *find_dsq_for_dispatch(struct scx_sched *sch,
 	return dsq;
 }
 
-static void mark_direct_dispatch(struct task_struct *ddsp_task,
+static void mark_direct_dispatch(struct scx_sched *sch,
+				 struct task_struct *ddsp_task,
 				 struct task_struct *p, u64 dsq_id,
 				 u64 enq_flags)
 {
@@ -1129,10 +1114,10 @@ static void mark_direct_dispatch(struct task_struct *ddsp_task,
 	/* @p must match the task on the enqueue path */
 	if (unlikely(p != ddsp_task)) {
 		if (IS_ERR(ddsp_task))
-			scx_kf_error("%s[%d] already direct-dispatched",
+			scx_error(sch, "%s[%d] already direct-dispatched",
 				  p->comm, p->pid);
 		else
-			scx_kf_error("scheduling for %s[%d] but trying to direct-dispatch %s[%d]",
+			scx_error(sch, "scheduling for %s[%d] but trying to direct-dispatch %s[%d]",
 				  ddsp_task->comm, ddsp_task->pid,
 				  p->comm, p->pid);
 		return;
@@ -5243,18 +5228,18 @@ void __init init_sched_ext_class(void)
 static bool scx_dsq_insert_preamble(struct scx_sched *sch, struct task_struct *p,
 				    u64 enq_flags)
 {
-	if (!scx_kf_allowed(SCX_KF_ENQUEUE | SCX_KF_DISPATCH))
+	if (!scx_kf_allowed(sch, SCX_KF_ENQUEUE | SCX_KF_DISPATCH))
 		return false;
 
 	lockdep_assert_irqs_disabled();
 
 	if (unlikely(!p)) {
-		scx_kf_error("called with NULL task");
+		scx_error(sch, "called with NULL task");
 		return false;
 	}
 
 	if (unlikely(enq_flags & __SCX_ENQ_INTERNAL_MASK)) {
-		scx_kf_error("invalid enq_flags 0x%llx", enq_flags);
+		scx_error(sch, "invalid enq_flags 0x%llx", enq_flags);
 		return false;
 	}
 
@@ -5269,12 +5254,12 @@ static void scx_dsq_insert_commit(struct scx_sched *sch, struct task_struct *p,
 
 	ddsp_task = __this_cpu_read(direct_dispatch_task);
 	if (ddsp_task) {
-		mark_direct_dispatch(ddsp_task, p, dsq_id, enq_flags);
+		mark_direct_dispatch(sch, ddsp_task, p, dsq_id, enq_flags);
 		return;
 	}
 
 	if (unlikely(dspc->cursor >= scx_dsp_max_batch)) {
-		scx_kf_error("dispatch buffer overflow");
+		scx_error(sch, "dispatch buffer overflow");
 		return;
 	}
 
@@ -5410,7 +5395,8 @@ static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit,
 	bool in_balance;
 	unsigned long flags;
 
-	if (!scx_kf_allowed_if_unlocked() && !scx_kf_allowed(SCX_KF_DISPATCH))
+	if (!scx_kf_allowed_if_unlocked() &&
+	    !scx_kf_allowed(sch, SCX_KF_DISPATCH))
 		return false;
 
 	/*
@@ -5495,7 +5481,15 @@ __bpf_kfunc_start_defs();
  */
 __bpf_kfunc u32 scx_bpf_dispatch_nr_slots(void)
 {
-	if (!scx_kf_allowed(SCX_KF_DISPATCH))
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return 0;
+
+	if (!scx_kf_allowed(sch, SCX_KF_DISPATCH))
 		return 0;
 
 	return scx_dsp_max_batch - __this_cpu_read(scx_dsp_ctx->cursor);
@@ -5510,14 +5504,21 @@ __bpf_kfunc u32 scx_bpf_dispatch_nr_slots(void)
 __bpf_kfunc void scx_bpf_dispatch_cancel(void)
 {
 	struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx);
+	struct scx_sched *sch;
 
-	if (!scx_kf_allowed(SCX_KF_DISPATCH))
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return;
+
+	if (!scx_kf_allowed(sch, SCX_KF_DISPATCH))
 		return;
 
 	if (dspc->cursor > 0)
 		dspc->cursor--;
 	else
-		scx_kf_error("dispatch buffer underflow");
+		scx_error(sch, "dispatch buffer underflow");
 }
 
 /**
@@ -5540,7 +5541,7 @@ __bpf_kfunc bool scx_bpf_dsq_move_to_local(u64 dsq_id)
 	struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx);
 	struct scx_dispatch_q *dsq;
 
-	if (!scx_kf_allowed(SCX_KF_DISPATCH))
+	if (!scx_kf_allowed(sch, SCX_KF_DISPATCH))
 		return false;
 
 	flush_dispatch_buf(sch, dspc->rq);
@@ -5687,12 +5688,18 @@ __bpf_kfunc_start_defs();
  */
 __bpf_kfunc u32 scx_bpf_reenqueue_local(void)
 {
+	struct scx_sched *sch;
 	LIST_HEAD(tasks);
 	u32 nr_enqueued = 0;
 	struct rq *rq;
 	struct task_struct *p, *n;
 
-	if (!scx_kf_allowed(SCX_KF_CPU_RELEASE))
+	guard(rcu)();
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return 0;
+
+	if (!scx_kf_allowed(sch, SCX_KF_CPU_RELEASE))
 		return 0;
 
 	rq = cpu_rq(smp_processor_id());
@@ -5837,7 +5844,7 @@ static void scx_kick_cpu(struct scx_sched *sch, s32 cpu, u64 flags)
 		struct rq *target_rq = cpu_rq(cpu);
 
 		if (unlikely(flags & (SCX_KICK_PREEMPT | SCX_KICK_WAIT)))
-			scx_kf_error("PREEMPT/WAIT cannot be used with SCX_KICK_IDLE");
+			scx_error(sch, "PREEMPT/WAIT cannot be used with SCX_KICK_IDLE");
 
 		if (raw_spin_rq_trylock(target_rq)) {
 			if (can_skip_idle_kick(target_rq)) {
@@ -6070,20 +6077,20 @@ static s32 __bstr_format(struct scx_sched *sch, u64 *data_buf, char *line_buf,
 
 	if (data__sz % 8 || data__sz > MAX_BPRINTF_VARARGS * 8 ||
 	    (data__sz && !data)) {
-		scx_kf_error("invalid data=%p and data__sz=%u", (void *)data, data__sz);
+		scx_error(sch, "invalid data=%p and data__sz=%u", (void *)data, data__sz);
 		return -EINVAL;
 	}
 
 	ret = copy_from_kernel_nofault(data_buf, data, data__sz);
 	if (ret < 0) {
-		scx_kf_error("failed to read data fields (%d)", ret);
+		scx_error(sch, "failed to read data fields (%d)", ret);
 		return ret;
 	}
 
 	ret = bpf_bprintf_prepare(fmt, UINT_MAX, data_buf, data__sz / 8,
 				  &bprintf_data);
 	if (ret < 0) {
-		scx_kf_error("format preparation failed (%d)", ret);
+		scx_error(sch, "format preparation failed (%d)", ret);
 		return ret;
 	}
 
@@ -6091,7 +6098,7 @@ static s32 __bstr_format(struct scx_sched *sch, u64 *data_buf, char *line_buf,
 			  bprintf_data.bin_args);
 	bpf_bprintf_cleanup(&bprintf_data);
 	if (ret < 0) {
-		scx_kf_error("(\"%s\", %p, %u) failed to format", fmt, data, data__sz);
+		scx_error(sch, "(\"%s\", %p, %u) failed to format", fmt, data, data__sz);
 		return ret;
 	}
 
@@ -6127,7 +6134,7 @@ __bpf_kfunc void scx_bpf_exit_bstr(s64 exit_code, char *fmt,
 	sch = rcu_dereference_bh(scx_root);
 	if (likely(sch) &&
 	    bstr_format(sch, &scx_exit_bstr_buf, fmt, data, data__sz) >= 0)
-		scx_kf_exit(SCX_EXIT_UNREG_BPF, exit_code, "%s", scx_exit_bstr_buf.line);
+		scx_exit(sch, SCX_EXIT_UNREG_BPF, exit_code, "%s", scx_exit_bstr_buf.line);
 	raw_spin_unlock_irqrestore(&scx_exit_bstr_buf_lock, flags);
 }
 
@@ -6150,7 +6157,7 @@ __bpf_kfunc void scx_bpf_error_bstr(char *fmt, unsigned long long *data,
 	sch = rcu_dereference_bh(scx_root);
 	if (likely(sch) &&
 	    bstr_format(sch, &scx_exit_bstr_buf, fmt, data, data__sz) >= 0)
-		scx_kf_exit(SCX_EXIT_ERROR_BPF, 0, "%s", scx_exit_bstr_buf.line);
+		scx_exit(sch, SCX_EXIT_ERROR_BPF, 0, "%s", scx_exit_bstr_buf.line);
 	raw_spin_unlock_irqrestore(&scx_exit_bstr_buf_lock, flags);
 }
 
@@ -6181,7 +6188,7 @@ __bpf_kfunc void scx_bpf_dump_bstr(char *fmt, unsigned long long *data,
 		return;
 
 	if (raw_smp_processor_id() != dd->cpu) {
-		scx_kf_error("scx_bpf_dump() must only be called from ops.dump() and friends");
+		scx_error(sch, "scx_bpf_dump() must only be called from ops.dump() and friends");
 		return;
 	}
 
@@ -6285,7 +6292,7 @@ __bpf_kfunc void scx_bpf_cpuperf_set(s32 cpu, u32 perf)
 		return;
 
 	if (unlikely(perf > SCX_CPUPERF_ONE)) {
-		scx_kf_error("Invalid cpuperf target %u for CPU %d", perf, cpu);
+		scx_error(sch, "Invalid cpuperf target %u for CPU %d", perf, cpu);
 		return;
 	}
 
@@ -6298,7 +6305,7 @@ __bpf_kfunc void scx_bpf_cpuperf_set(s32 cpu, u32 perf)
 		 * to the corresponding CPU to prevent ABBA deadlocks.
 		 */
 		if (locked_rq && rq != locked_rq) {
-			scx_kf_error("Invalid target CPU %d", cpu);
+			scx_error(sch, "Invalid target CPU %d", cpu);
 			return;
 		}
 
@@ -6422,16 +6429,20 @@ __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu)
  */
 __bpf_kfunc struct rq *scx_bpf_locked_rq(void)
 {
+	struct scx_sched *sch;
 	struct rq *rq;
 
-	preempt_disable();
+	guard(preempt)();
+
+	sch = rcu_dereference_sched(scx_root);
+	if (unlikely(!sch))
+		return NULL;
+
 	rq = scx_locked_rq();
 	if (!rq) {
-		preempt_enable();
-		scx_kf_error("accessing rq without holding rq lock");
+		scx_error(sch, "accessing rq without holding rq lock");
 		return NULL;
 	}
-	preempt_enable();
 
 	return rq;
 }
@@ -6474,8 +6485,15 @@ __bpf_kfunc struct cgroup *scx_bpf_task_cgroup(struct task_struct *p)
 {
 	struct task_group *tg = p->sched_task_group;
 	struct cgroup *cgrp = &cgrp_dfl_root.cgrp;
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		goto out;
 
-	if (!scx_kf_allowed_on_arg_tasks(__SCX_KF_RQ_LOCKED, p))
+	if (!scx_kf_allowed_on_arg_tasks(sch, __SCX_KF_RQ_LOCKED, p))
 		goto out;
 
 	cgrp = tg_cgrp(tg);
diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
index a576ec10522e..c57779f0ad57 100644
--- a/kernel/sched/ext_idle.c
+++ b/kernel/sched/ext_idle.c
@@ -822,7 +822,7 @@ void scx_idle_disable(void)
 static int validate_node(struct scx_sched *sch, int node)
 {
 	if (!static_branch_likely(&scx_builtin_idle_per_node)) {
-		scx_kf_error("per-node idle tracking is disabled");
+		scx_error(sch, "per-node idle tracking is disabled");
 		return -EOPNOTSUPP;
 	}
 
@@ -832,13 +832,13 @@ static int validate_node(struct scx_sched *sch, int node)
 
 	/* Make sure node is in a valid range */
 	if (node < 0 || node >= nr_node_ids) {
-		scx_kf_error("invalid node %d", node);
+		scx_error(sch, "invalid node %d", node);
 		return -EINVAL;
 	}
 
 	/* Make sure the node is part of the set of possible nodes */
 	if (!node_possible(node)) {
-		scx_kf_error("unavailable node %d", node);
+		scx_error(sch, "unavailable node %d", node);
 		return -EINVAL;
 	}
 
@@ -852,7 +852,7 @@ static bool check_builtin_idle_enabled(struct scx_sched *sch)
 	if (static_branch_likely(&scx_builtin_idle_enabled))
 		return true;
 
-	scx_kf_error("built-in idle tracking is disabled");
+	scx_error(sch, "built-in idle tracking is disabled");
 	return false;
 }
 
@@ -880,7 +880,7 @@ static s32 select_cpu_from_kfunc(struct scx_sched *sch, struct task_struct *p,
 	if (scx_kf_allowed_if_unlocked()) {
 		rq = task_rq_lock(p, &rf);
 	} else {
-		if (!scx_kf_allowed(SCX_KF_SELECT_CPU | SCX_KF_ENQUEUE))
+		if (!scx_kf_allowed(sch, SCX_KF_SELECT_CPU | SCX_KF_ENQUEUE))
 			return -EPERM;
 		rq = scx_locked_rq();
 	}
@@ -1048,7 +1048,7 @@ __bpf_kfunc const struct cpumask *scx_bpf_get_idle_cpumask(void)
 		return cpu_none_mask;
 
 	if (static_branch_unlikely(&scx_builtin_idle_per_node)) {
-		scx_kf_error("SCX_OPS_BUILTIN_IDLE_PER_NODE enabled");
+		scx_error(sch, "SCX_OPS_BUILTIN_IDLE_PER_NODE enabled");
 		return cpu_none_mask;
 	}
 
@@ -1107,7 +1107,7 @@ __bpf_kfunc const struct cpumask *scx_bpf_get_idle_smtmask(void)
 		return cpu_none_mask;
 
 	if (static_branch_unlikely(&scx_builtin_idle_per_node)) {
-		scx_kf_error("SCX_OPS_BUILTIN_IDLE_PER_NODE enabled");
+		scx_error(sch, "SCX_OPS_BUILTIN_IDLE_PER_NODE enabled");
 		return cpu_none_mask;
 	}
 
@@ -1235,7 +1235,7 @@ __bpf_kfunc s32 scx_bpf_pick_idle_cpu(const struct cpumask *cpus_allowed,
 		return -ENODEV;
 
 	if (static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) {
-		scx_kf_error("per-node idle tracking is enabled");
+		scx_error(sch, "per-node idle tracking is enabled");
 		return -EBUSY;
 	}
 
@@ -1316,10 +1316,17 @@ __bpf_kfunc s32 scx_bpf_pick_any_cpu_node(const struct cpumask *cpus_allowed,
 __bpf_kfunc s32 scx_bpf_pick_any_cpu(const struct cpumask *cpus_allowed,
 				     u64 flags)
 {
+	struct scx_sched *sch;
 	s32 cpu;
 
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return -ENODEV;
+
 	if (static_branch_maybe(CONFIG_NUMA, &scx_builtin_idle_per_node)) {
-		scx_kf_error("per-node idle tracking is enabled");
+		scx_error(sch, "per-node idle tracking is enabled");
 		return -EBUSY;
 	}
 
-- 
2.51.0

[PATCH 7/7] sched_ext: Misc updates around scx_sched instance pointer

[Tejun Heo]

In preparation for multiple scheduler support:

- Add the @sch parameter to find_global_dsq() and refill_task_slice_dfl().

- Restructure scx_allow_ttwu_queue() and make it read scx_root into $sch.

- Make RCU protection in scx_dsq_move() and scx_bpf_dsq_move_to_local()
  explicit.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c | 62 ++++++++++++++++++++++++++++++----------------
 1 file changed, 40 insertions(+), 22 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 0c99a55f199b..32306203fba5 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -181,10 +181,9 @@ static bool u32_before(u32 a, u32 b)
 	return (s32)(a - b) < 0;
 }
 
-static struct scx_dispatch_q *find_global_dsq(struct task_struct *p)
+static struct scx_dispatch_q *find_global_dsq(struct scx_sched *sch,
+					      struct task_struct *p)
 {
-	struct scx_sched *sch = scx_root;
-
 	return sch->global_dsqs[cpu_to_node(task_cpu(p))];
 }
 
@@ -880,10 +879,10 @@ static void dsq_mod_nr(struct scx_dispatch_q *dsq, s32 delta)
 	WRITE_ONCE(dsq->nr, dsq->nr + delta);
 }
 
-static void refill_task_slice_dfl(struct task_struct *p)
+static void refill_task_slice_dfl(struct scx_sched *sch, struct task_struct *p)
 {
 	p->scx.slice = SCX_SLICE_DFL;
-	__scx_add_event(scx_root, SCX_EV_REFILL_SLICE_DFL, 1);
+	__scx_add_event(sch, SCX_EV_REFILL_SLICE_DFL, 1);
 }
 
 static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq,
@@ -901,7 +900,7 @@ static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq,
 			scx_error(sch, "attempting to dispatch to a destroyed dsq");
 			/* fall back to the global dsq */
 			raw_spin_unlock(&dsq->lock);
-			dsq = find_global_dsq(p);
+			dsq = find_global_dsq(sch, p);
 			raw_spin_lock(&dsq->lock);
 		}
 	}
@@ -1080,20 +1079,20 @@ static struct scx_dispatch_q *find_dsq_for_dispatch(struct scx_sched *sch,
 		s32 cpu = dsq_id & SCX_DSQ_LOCAL_CPU_MASK;
 
 		if (!ops_cpu_valid(sch, cpu, "in SCX_DSQ_LOCAL_ON dispatch verdict"))
-			return find_global_dsq(p);
+			return find_global_dsq(sch, p);
 
 		return &cpu_rq(cpu)->scx.local_dsq;
 	}
 
 	if (dsq_id == SCX_DSQ_GLOBAL)
-		dsq = find_global_dsq(p);
+		dsq = find_global_dsq(sch, p);
 	else
 		dsq = find_user_dsq(sch, dsq_id);
 
 	if (unlikely(!dsq)) {
 		scx_error(sch, "non-existent DSQ 0x%llx for %s[%d]",
 			  dsq_id, p->comm, p->pid);
-		return find_global_dsq(p);
+		return find_global_dsq(sch, p);
 	}
 
 	return dsq;
@@ -1272,15 +1271,15 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
 	 * higher priority it becomes from scx_prio_less()'s POV.
 	 */
 	touch_core_sched(rq, p);
-	refill_task_slice_dfl(p);
+	refill_task_slice_dfl(sch, p);
 local_norefill:
 	dispatch_enqueue(sch, &rq->scx.local_dsq, p, enq_flags);
 	return;
 
 global:
 	touch_core_sched(rq, p);	/* see the comment in local: */
-	refill_task_slice_dfl(p);
-	dispatch_enqueue(sch, find_global_dsq(p), p, enq_flags);
+	refill_task_slice_dfl(sch, p);
+	dispatch_enqueue(sch, find_global_dsq(sch, p), p, enq_flags);
 }
 
 static bool task_runnable(const struct task_struct *p)
@@ -1692,7 +1691,7 @@ static struct rq *move_task_between_dsqs(struct scx_sched *sch,
 		dst_rq = container_of(dst_dsq, struct rq, scx.local_dsq);
 		if (src_rq != dst_rq &&
 		    unlikely(!task_can_run_on_remote_rq(sch, p, dst_rq, true))) {
-			dst_dsq = find_global_dsq(p);
+			dst_dsq = find_global_dsq(sch, p);
 			dst_rq = src_rq;
 		}
 	} else {
@@ -1848,7 +1847,7 @@ static void dispatch_to_local_dsq(struct scx_sched *sch, struct rq *rq,
 
 	if (src_rq != dst_rq &&
 	    unlikely(!task_can_run_on_remote_rq(sch, p, dst_rq, true))) {
-		dispatch_enqueue(sch, find_global_dsq(p), p,
+		dispatch_enqueue(sch, find_global_dsq(sch, p), p,
 				 enq_flags | SCX_ENQ_CLEAR_OPSS);
 		return;
 	}
@@ -2380,7 +2379,7 @@ static struct task_struct *pick_task_scx(struct rq *rq)
 	if (keep_prev) {
 		p = prev;
 		if (!p->scx.slice)
-			refill_task_slice_dfl(p);
+			refill_task_slice_dfl(rcu_dereference_sched(scx_root), p);
 	} else {
 		p = first_local_task(rq);
 		if (!p) {
@@ -2391,14 +2390,14 @@ static struct task_struct *pick_task_scx(struct rq *rq)
 		}
 
 		if (unlikely(!p->scx.slice)) {
-			struct scx_sched *sch = scx_root;
+			struct scx_sched *sch = rcu_dereference_sched(scx_root);
 
 			if (!scx_rq_bypassing(rq) && !sch->warned_zero_slice) {
 				printk_deferred(KERN_WARNING "sched_ext: %s[%d] has zero slice in %s()\n",
 						p->comm, p->pid, __func__);
 				sch->warned_zero_slice = true;
 			}
-			refill_task_slice_dfl(p);
+			refill_task_slice_dfl(sch, p);
 		}
 	}
 
@@ -2487,7 +2486,7 @@ static int select_task_rq_scx(struct task_struct *p, int prev_cpu, int wake_flag
 
 		cpu = scx_select_cpu_dfl(p, prev_cpu, wake_flags, NULL, 0);
 		if (cpu >= 0) {
-			refill_task_slice_dfl(p);
+			refill_task_slice_dfl(sch, p);
 			p->scx.ddsp_dsq_id = SCX_DSQ_LOCAL;
 		} else {
 			cpu = prev_cpu;
@@ -3572,9 +3571,22 @@ bool task_should_scx(int policy)
 
 bool scx_allow_ttwu_queue(const struct task_struct *p)
 {
-	return !scx_enabled() ||
-		(scx_root->ops.flags & SCX_OPS_ALLOW_QUEUED_WAKEUP) ||
-		p->sched_class != &ext_sched_class;
+	struct scx_sched *sch;
+
+	if (!scx_enabled())
+		return true;
+
+	sch = rcu_dereference_sched(scx_root);
+	if (unlikely(!sch))
+		return true;
+
+	if (scx_root->ops.flags & SCX_OPS_ALLOW_QUEUED_WAKEUP)
+		return true;
+
+	if (unlikely(p->sched_class != &ext_sched_class))
+		return true;
+
+	return false;
 }
 
 /**
@@ -5537,9 +5549,15 @@ __bpf_kfunc void scx_bpf_dispatch_cancel(void)
  */
 __bpf_kfunc bool scx_bpf_dsq_move_to_local(u64 dsq_id)
 {
-	struct scx_sched *sch = scx_root;
 	struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx);
 	struct scx_dispatch_q *dsq;
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return false;
 
 	if (!scx_kf_allowed(sch, SCX_KF_DISPATCH))
 		return false;
-- 
2.51.0

Re: [PATCH 7/7] sched_ext: Misc updates around scx_sched instance pointer

[Andrea Righi]

Hi Tejun,

On Mon, Sep 22, 2025 at 06:14:36AM -1000, Tejun Heo wrote:
> In preparation for multiple scheduler support:
> 
> - Add the @sch parameter to find_global_dsq() and refill_task_slice_dfl().
> 
> - Restructure scx_allow_ttwu_queue() and make it read scx_root into $sch.
> 
> - Make RCU protection in scx_dsq_move() and scx_bpf_dsq_move_to_local()
>   explicit.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> ---
>  kernel/sched/ext.c | 62 ++++++++++++++++++++++++++++++----------------
>  1 file changed, 40 insertions(+), 22 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 0c99a55f199b..32306203fba5 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
...
> @@ -3572,9 +3571,22 @@ bool task_should_scx(int policy)
>  
>  bool scx_allow_ttwu_queue(const struct task_struct *p)
>  {
> -	return !scx_enabled() ||
> -		(scx_root->ops.flags & SCX_OPS_ALLOW_QUEUED_WAKEUP) ||
> -		p->sched_class != &ext_sched_class;
> +	struct scx_sched *sch;
> +
> +	if (!scx_enabled())
> +		return true;
> +
> +	sch = rcu_dereference_sched(scx_root);
> +	if (unlikely(!sch))
> +		return true;
> +
> +	if (scx_root->ops.flags & SCX_OPS_ALLOW_QUEUED_WAKEUP)

We should use sch->ops.flags here.

> +		return true;
> +
> +	if (unlikely(p->sched_class != &ext_sched_class))
> +		return true;
> +
> +	return false;
>  }

Thanks,
-Andrea

Re: [PATCHSET sched_ext/scx-misc-a] sched_ext: Add @sch parameter in preparation for multi-sched support

[Andrea Righi]

Hi Tejun,

On Mon, Sep 22, 2025 at 06:14:29AM -1000, Tejun Heo wrote:
> This patchset systematically adds the @sch parameter to various sched_ext
> functions in preparation for multiple scheduler support. This part is
> needed regardless of how the rest of the multiple scheduler patchset
> develops. The changes also remove a bunch of naked scx_root dereferences
> that trigger sparse warnings. The changes are mostly mechanical parameter
> additions without functional changes.
> 
> The patches are based on sched_ext/for-6.18 (ac6772e8bcda) +
> "sched_ext: misc cleanups and improvements"
> (http://lkml.kernel.org/r/20250922013246.275031-1-tj@kernel.org).
> 
>  1 sched_ext: Separate out scx_kick_cpu() and add @sch to it
>  2 sched_ext: Add the @sch parameter to __bstr_format()
>  3 sched_ext: Add the @sch parameter to ext_idle helpers
>  4 sched_ext: Drop kf_cpu_valid()
>  5 sched_ext: Add the @sch parameter to scx_dsq_insert_preamble/commit()
>  6 sched_ext: Drop scx_kf_exit() and scx_kf_error()
>  7 sched_ext: Misc updates around scx_sched instance pointer

I just found a small issue in PATCH 7/7, but everything else looks good to
me. With the fixed PATCH 7 you can add my:

Reviewed-by: Andrea Righi <arighi@nvidia.com>

Thanks,
-Andrea

> 
> The following git tree also contains the patchset:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-sub-sched-misc-prep
> 
>  kernel/sched/ext.c      | 355 ++++++++++++++++++++++++++++++------------------
>  kernel/sched/ext_idle.c | 146 ++++++++++++++++----
>  2 files changed, 340 insertions(+), 161 deletions(-)
> 
> --
> tejun

[PATCH v2 7/7] sched_ext: Misc updates around scx_sched instance pointer

[Tejun Heo]

In preparation for multiple scheduler support:

- Add the @sch parameter to find_global_dsq() and refill_task_slice_dfl().

- Restructure scx_allow_ttwu_queue() and make it read scx_root into $sch.

- Make RCU protection in scx_dsq_move() and scx_bpf_dsq_move_to_local()
  explicit.

v2: Add scx_root -> sch conversion in scx_allow_ttwu_queue().

Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c |   62 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 40 insertions(+), 22 deletions(-)

--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -181,10 +181,9 @@ static bool u32_before(u32 a, u32 b)
 	return (s32)(a - b) < 0;
 }
 
-static struct scx_dispatch_q *find_global_dsq(struct task_struct *p)
+static struct scx_dispatch_q *find_global_dsq(struct scx_sched *sch,
+					      struct task_struct *p)
 {
-	struct scx_sched *sch = scx_root;
-
 	return sch->global_dsqs[cpu_to_node(task_cpu(p))];
 }
 
@@ -880,10 +879,10 @@ static void dsq_mod_nr(struct scx_dispat
 	WRITE_ONCE(dsq->nr, dsq->nr + delta);
 }
 
-static void refill_task_slice_dfl(struct task_struct *p)
+static void refill_task_slice_dfl(struct scx_sched *sch, struct task_struct *p)
 {
 	p->scx.slice = SCX_SLICE_DFL;
-	__scx_add_event(scx_root, SCX_EV_REFILL_SLICE_DFL, 1);
+	__scx_add_event(sch, SCX_EV_REFILL_SLICE_DFL, 1);
 }
 
 static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq,
@@ -901,7 +900,7 @@ static void dispatch_enqueue(struct scx_
 			scx_error(sch, "attempting to dispatch to a destroyed dsq");
 			/* fall back to the global dsq */
 			raw_spin_unlock(&dsq->lock);
-			dsq = find_global_dsq(p);
+			dsq = find_global_dsq(sch, p);
 			raw_spin_lock(&dsq->lock);
 		}
 	}
@@ -1080,20 +1079,20 @@ static struct scx_dispatch_q *find_dsq_f
 		s32 cpu = dsq_id & SCX_DSQ_LOCAL_CPU_MASK;
 
 		if (!ops_cpu_valid(sch, cpu, "in SCX_DSQ_LOCAL_ON dispatch verdict"))
-			return find_global_dsq(p);
+			return find_global_dsq(sch, p);
 
 		return &cpu_rq(cpu)->scx.local_dsq;
 	}
 
 	if (dsq_id == SCX_DSQ_GLOBAL)
-		dsq = find_global_dsq(p);
+		dsq = find_global_dsq(sch, p);
 	else
 		dsq = find_user_dsq(sch, dsq_id);
 
 	if (unlikely(!dsq)) {
 		scx_error(sch, "non-existent DSQ 0x%llx for %s[%d]",
 			  dsq_id, p->comm, p->pid);
-		return find_global_dsq(p);
+		return find_global_dsq(sch, p);
 	}
 
 	return dsq;
@@ -1272,15 +1271,15 @@ local:
 	 * higher priority it becomes from scx_prio_less()'s POV.
 	 */
 	touch_core_sched(rq, p);
-	refill_task_slice_dfl(p);
+	refill_task_slice_dfl(sch, p);
 local_norefill:
 	dispatch_enqueue(sch, &rq->scx.local_dsq, p, enq_flags);
 	return;
 
 global:
 	touch_core_sched(rq, p);	/* see the comment in local: */
-	refill_task_slice_dfl(p);
-	dispatch_enqueue(sch, find_global_dsq(p), p, enq_flags);
+	refill_task_slice_dfl(sch, p);
+	dispatch_enqueue(sch, find_global_dsq(sch, p), p, enq_flags);
 }
 
 static bool task_runnable(const struct task_struct *p)
@@ -1692,7 +1691,7 @@ static struct rq *move_task_between_dsqs
 		dst_rq = container_of(dst_dsq, struct rq, scx.local_dsq);
 		if (src_rq != dst_rq &&
 		    unlikely(!task_can_run_on_remote_rq(sch, p, dst_rq, true))) {
-			dst_dsq = find_global_dsq(p);
+			dst_dsq = find_global_dsq(sch, p);
 			dst_rq = src_rq;
 		}
 	} else {
@@ -1848,7 +1847,7 @@ static void dispatch_to_local_dsq(struct
 
 	if (src_rq != dst_rq &&
 	    unlikely(!task_can_run_on_remote_rq(sch, p, dst_rq, true))) {
-		dispatch_enqueue(sch, find_global_dsq(p), p,
+		dispatch_enqueue(sch, find_global_dsq(sch, p), p,
 				 enq_flags | SCX_ENQ_CLEAR_OPSS);
 		return;
 	}
@@ -2380,7 +2379,7 @@ static struct task_struct *pick_task_scx
 	if (keep_prev) {
 		p = prev;
 		if (!p->scx.slice)
-			refill_task_slice_dfl(p);
+			refill_task_slice_dfl(rcu_dereference_sched(scx_root), p);
 	} else {
 		p = first_local_task(rq);
 		if (!p) {
@@ -2391,14 +2390,14 @@ static struct task_struct *pick_task_scx
 		}
 
 		if (unlikely(!p->scx.slice)) {
-			struct scx_sched *sch = scx_root;
+			struct scx_sched *sch = rcu_dereference_sched(scx_root);
 
 			if (!scx_rq_bypassing(rq) && !sch->warned_zero_slice) {
 				printk_deferred(KERN_WARNING "sched_ext: %s[%d] has zero slice in %s()\n",
 						p->comm, p->pid, __func__);
 				sch->warned_zero_slice = true;
 			}
-			refill_task_slice_dfl(p);
+			refill_task_slice_dfl(sch, p);
 		}
 	}
 
@@ -2487,7 +2486,7 @@ static int select_task_rq_scx(struct tas
 
 		cpu = scx_select_cpu_dfl(p, prev_cpu, wake_flags, NULL, 0);
 		if (cpu >= 0) {
-			refill_task_slice_dfl(p);
+			refill_task_slice_dfl(sch, p);
 			p->scx.ddsp_dsq_id = SCX_DSQ_LOCAL;
 		} else {
 			cpu = prev_cpu;
@@ -3572,9 +3571,22 @@ bool task_should_scx(int policy)
 
 bool scx_allow_ttwu_queue(const struct task_struct *p)
 {
-	return !scx_enabled() ||
-		(scx_root->ops.flags & SCX_OPS_ALLOW_QUEUED_WAKEUP) ||
-		p->sched_class != &ext_sched_class;
+	struct scx_sched *sch;
+
+	if (!scx_enabled())
+		return true;
+
+	sch = rcu_dereference_sched(scx_root);
+	if (unlikely(!sch))
+		return true;
+
+	if (sch->ops.flags & SCX_OPS_ALLOW_QUEUED_WAKEUP)
+		return true;
+
+	if (unlikely(p->sched_class != &ext_sched_class))
+		return true;
+
+	return false;
 }
 
 /**
@@ -5541,9 +5553,15 @@ __bpf_kfunc void scx_bpf_dispatch_cancel
  */
 __bpf_kfunc bool scx_bpf_dsq_move_to_local(u64 dsq_id)
 {
-	struct scx_sched *sch = scx_root;
 	struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx);
 	struct scx_dispatch_q *dsq;
+	struct scx_sched *sch;
+
+	guard(rcu)();
+
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return false;
 
 	if (!scx_kf_allowed(sch, SCX_KF_DISPATCH))
 		return false;

Re: [PATCHSET sched_ext/scx-misc-a] sched_ext: Add @sch parameter in preparation for multi-sched support

[Tejun Heo]

On Mon, Sep 22, 2025 at 06:14:29AM -1000, Tejun Heo wrote:
> This patchset systematically adds the @sch parameter to various sched_ext
> functions in preparation for multiple scheduler support. This part is
> needed regardless of how the rest of the multiple scheduler patchset
> develops. The changes also remove a bunch of naked scx_root dereferences
> that trigger sparse warnings. The changes are mostly mechanical parameter
> additions without functional changes.
> 
> The patches are based on sched_ext/for-6.18 (ac6772e8bcda) +
> "sched_ext: misc cleanups and improvements"
> (http://lkml.kernel.org/r/20250922013246.275031-1-tj@kernel.org).
> 
>  1 sched_ext: Separate out scx_kick_cpu() and add @sch to it
>  2 sched_ext: Add the @sch parameter to __bstr_format()
>  3 sched_ext: Add the @sch parameter to ext_idle helpers
>  4 sched_ext: Drop kf_cpu_valid()
>  5 sched_ext: Add the @sch parameter to scx_dsq_insert_preamble/commit()
>  6 sched_ext: Drop scx_kf_exit() and scx_kf_error()
>  7 sched_ext: Misc updates around scx_sched instance pointer

Applied to sched_ext/for-6.18.

Thanks.

-- 
tejun