[PATCH 3/5] sched/debug: Make CONFIG_SCHED_DEBUG functionality unconditional

From: Ingo Molnar
Date: Mon Mar 17 2025 - 06:48:21 EST

All the big Linux distros enable CONFIG_SCHED_DEBUG, because
the various features it provides help not just with kernel
development, but with system administration and user-space
software development as well.

Reflect this reality and enable this functionality
unconditionally.

Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
fs/proc/base.c | 7 -------
include/linux/energy_model.h | 2 --
include/linux/sched/debug.h | 2 --
include/linux/sched/topology.h | 4 ----
include/trace/events/sched.h | 2 --
kernel/sched/build_utility.c | 4 +---
kernel/sched/core.c | 18 +++---------------
kernel/sched/deadline.c | 2 --
kernel/sched/fair.c | 4 ----
kernel/sched/rt.c | 5 +----
kernel/sched/sched.h | 54 ++++--------------------------------------------------
kernel/sched/topology.c | 13 -------------
12 files changed, 9 insertions(+), 108 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index cd89e956c322..61526420d0ee 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1489,7 +1489,6 @@ static const struct file_operations proc_fail_nth_operations = {
#endif


-#ifdef CONFIG_SCHED_DEBUG
/*
* Print out various scheduling related per-task fields:
*/
@@ -1539,8 +1538,6 @@ static const struct file_operations proc_pid_sched_operations = {
.release = single_release,
};

-#endif
-
#ifdef CONFIG_SCHED_AUTOGROUP
/*
* Print out autogroup related information:
@@ -3331,9 +3328,7 @@ static const struct pid_entry tgid_base_stuff[] = {
ONE("status", S_IRUGO, proc_pid_status),
ONE("personality", S_IRUSR, proc_pid_personality),
ONE("limits", S_IRUGO, proc_pid_limits),
-#ifdef CONFIG_SCHED_DEBUG
REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations),
-#endif
#ifdef CONFIG_SCHED_AUTOGROUP
REG("autogroup", S_IRUGO|S_IWUSR, proc_pid_sched_autogroup_operations),
#endif
@@ -3682,9 +3677,7 @@ static const struct pid_entry tid_base_stuff[] = {
ONE("status", S_IRUGO, proc_pid_status),
ONE("personality", S_IRUSR, proc_pid_personality),
ONE("limits", S_IRUGO, proc_pid_limits),
-#ifdef CONFIG_SCHED_DEBUG
REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations),
-#endif
NOD("comm", S_IFREG|S_IRUGO|S_IWUSR,
&proc_tid_comm_inode_operations,
&proc_pid_set_comm_operations, {}),
diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index 78318d49276d..65efc0f5ea2e 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -240,9 +240,7 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
struct em_perf_state *ps;
int i;

-#ifdef CONFIG_SCHED_DEBUG
WARN_ONCE(!rcu_read_lock_held(), "EM: rcu read lock needed\n");
-#endif

if (!sum_util)
return 0;
diff --git a/include/linux/sched/debug.h b/include/linux/sched/debug.h
index b5035afa2396..35ed4577a6cc 100644
--- a/include/linux/sched/debug.h
+++ b/include/linux/sched/debug.h
@@ -35,12 +35,10 @@ extern void show_stack(struct task_struct *task, unsigned long *sp,

extern void sched_show_task(struct task_struct *p);

-#ifdef CONFIG_SCHED_DEBUG
struct seq_file;
extern void proc_sched_show_task(struct task_struct *p,
struct pid_namespace *ns, struct seq_file *m);
extern void proc_sched_set_task(struct task_struct *p);
-#endif

/* Attach to any functions which should be ignored in wchan output. */
#define __sched __section(".sched.text")
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 7f3dbafe1817..7894653bc70b 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -25,16 +25,12 @@ enum {
};
#undef SD_FLAG

-#ifdef CONFIG_SCHED_DEBUG
-
struct sd_flag_debug {
unsigned int meta_flags;
char *name;
};
extern const struct sd_flag_debug sd_flag_debug[];

-#endif
-
#ifdef CONFIG_SCHED_SMT
static inline int cpu_smt_flags(void)
{
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 9ea4c404bd4e..bfd97cce40a1 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -193,9 +193,7 @@ static inline long __trace_sched_switch_state(bool preempt,
{
unsigned int state;

-#ifdef CONFIG_SCHED_DEBUG
BUG_ON(p != current);
-#endif /* CONFIG_SCHED_DEBUG */

/*
* Preemption ignores task state, therefore preempted tasks are always
diff --git a/kernel/sched/build_utility.c b/kernel/sched/build_utility.c
index 80a3df49ab47..bf9d8db94b70 100644
--- a/kernel/sched/build_utility.c
+++ b/kernel/sched/build_utility.c
@@ -68,9 +68,7 @@
# include "cpufreq_schedutil.c"
#endif

-#ifdef CONFIG_SCHED_DEBUG
-# include "debug.c"
-#endif
+#include "debug.c"

#ifdef CONFIG_SCHEDSTATS
# include "stats.c"
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d6833a85e561..598b7f241dda 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -118,7 +118,6 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);

DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);

-#ifdef CONFIG_SCHED_DEBUG
/*
* Debugging: various feature bits
*
@@ -142,7 +141,6 @@ __read_mostly unsigned int sysctl_sched_features =
*/
__read_mostly int sysctl_resched_latency_warn_ms = 100;
__read_mostly int sysctl_resched_latency_warn_once = 1;
-#endif /* CONFIG_SCHED_DEBUG */

/*
* Number of tasks to iterate in a single balance run.
@@ -799,11 +797,10 @@ void update_rq_clock(struct rq *rq)
if (rq->clock_update_flags & RQCF_ACT_SKIP)
return;

-#ifdef CONFIG_SCHED_DEBUG
if (sched_feat(WARN_DOUBLE_CLOCK))
WARN_ON_ONCE(rq->clock_update_flags & RQCF_UPDATED);
rq->clock_update_flags |= RQCF_UPDATED;
-#endif
+
clock = sched_clock_cpu(cpu_of(rq));
scx_rq_clock_update(rq, clock);

@@ -3291,7 +3288,6 @@ void relax_compatible_cpus_allowed_ptr(struct task_struct *p)

void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
-#ifdef CONFIG_SCHED_DEBUG
unsigned int state = READ_ONCE(p->__state);

/*
@@ -3329,7 +3325,6 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
WARN_ON_ONCE(!cpu_online(new_cpu));

WARN_ON_ONCE(is_migration_disabled(p));
-#endif

trace_sched_migrate_task(p, new_cpu);

@@ -5577,7 +5572,6 @@ unsigned long long task_sched_runtime(struct task_struct *p)
return ns;
}

-#ifdef CONFIG_SCHED_DEBUG
static u64 cpu_resched_latency(struct rq *rq)
{
int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
@@ -5622,9 +5616,6 @@ static int __init setup_resched_latency_warn_ms(char *str)
return 1;
}
__setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
-#else
-static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
-#endif /* CONFIG_SCHED_DEBUG */

/*
* This function gets called by the timer code, with HZ frequency.
@@ -6718,9 +6709,7 @@ static void __sched notrace __schedule(int sched_mode)
picked:
clear_tsk_need_resched(prev);
clear_preempt_need_resched();
-#ifdef CONFIG_SCHED_DEBUG
rq->last_seen_need_resched_ns = 0;
-#endif

if (likely(prev != next)) {
rq->nr_switches++;
@@ -7094,7 +7083,7 @@ asmlinkage __visible void __sched preempt_schedule_irq(void)
int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
void *key)
{
- WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~(WF_SYNC|WF_CURRENT_CPU));
+ WARN_ON_ONCE(wake_flags & ~(WF_SYNC|WF_CURRENT_CPU));
return try_to_wake_up(curr->private, mode, wake_flags);
}
EXPORT_SYMBOL(default_wake_function);
@@ -7764,10 +7753,9 @@ void show_state_filter(unsigned int state_filter)
sched_show_task(p);
}

-#ifdef CONFIG_SCHED_DEBUG
if (!state_filter)
sysrq_sched_debug_show();
-#endif
+
rcu_read_unlock();
/*
* Only show locks if all tasks are dumped:
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index b18c80272f86..d352b57f31cf 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3567,9 +3567,7 @@ void dl_bw_free(int cpu, u64 dl_bw)
}
#endif

-#ifdef CONFIG_SCHED_DEBUG
void print_dl_stats(struct seq_file *m, int cpu)
{
print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
}
-#endif /* CONFIG_SCHED_DEBUG */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 35ee8d9d78d5..a0c4cd26ee07 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -983,7 +983,6 @@ static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
return best;
}

-#ifdef CONFIG_SCHED_DEBUG
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
{
struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
@@ -1010,7 +1009,6 @@ int sched_update_scaling(void)
return 0;
}
#endif
-#endif

static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se);

@@ -13668,7 +13666,6 @@ DEFINE_SCHED_CLASS(fair) = {
#endif
};

-#ifdef CONFIG_SCHED_DEBUG
void print_cfs_stats(struct seq_file *m, int cpu)
{
struct cfs_rq *cfs_rq, *pos;
@@ -13702,7 +13699,6 @@ void show_numa_stats(struct task_struct *p, struct seq_file *m)
rcu_read_unlock();
}
#endif /* CONFIG_NUMA_BALANCING */
-#endif /* CONFIG_SCHED_DEBUG */

__init void init_sched_fair_class(void)
{
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 926281ac3ac0..8f7c3bfb49ef 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -169,9 +169,8 @@ static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)

static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
{
-#ifdef CONFIG_SCHED_DEBUG
WARN_ON_ONCE(!rt_entity_is_task(rt_se));
-#endif
+
return container_of(rt_se, struct task_struct, rt);
}

@@ -2967,7 +2966,6 @@ static int sched_rr_handler(const struct ctl_table *table, int write, void *buff
}
#endif /* CONFIG_SYSCTL */

-#ifdef CONFIG_SCHED_DEBUG
void print_rt_stats(struct seq_file *m, int cpu)
{
rt_rq_iter_t iter;
@@ -2978,4 +2976,3 @@ void print_rt_stats(struct seq_file *m, int cpu)
print_rt_rq(m, cpu, rt_rq);
rcu_read_unlock();
}
-#endif /* CONFIG_SCHED_DEBUG */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 187a22800577..ac68db706b7c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1174,10 +1174,8 @@ struct rq {

atomic_t nr_iowait;

-#ifdef CONFIG_SCHED_DEBUG
u64 last_seen_need_resched_ns;
int ticks_without_resched;
-#endif

#ifdef CONFIG_MEMBARRIER
int membarrier_state;
@@ -1706,14 +1704,12 @@ static inline void rq_clock_stop_loop_update(struct rq *rq)
struct rq_flags {
unsigned long flags;
struct pin_cookie cookie;
-#ifdef CONFIG_SCHED_DEBUG
/*
* A copy of (rq::clock_update_flags & RQCF_UPDATED) for the
* current pin context is stashed here in case it needs to be
* restored in rq_repin_lock().
*/
unsigned int clock_update_flags;
-#endif
};

extern struct balance_callback balance_push_callback;
@@ -1764,21 +1760,18 @@ static inline void rq_pin_lock(struct rq *rq, struct rq_flags *rf)
{
rf->cookie = lockdep_pin_lock(__rq_lockp(rq));

-#ifdef CONFIG_SCHED_DEBUG
rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
rf->clock_update_flags = 0;
-# ifdef CONFIG_SMP
+#ifdef CONFIG_SMP
WARN_ON_ONCE(rq->balance_callback && rq->balance_callback != &balance_push_callback);
-# endif
#endif
}

static inline void rq_unpin_lock(struct rq *rq, struct rq_flags *rf)
{
-#ifdef CONFIG_SCHED_DEBUG
if (rq->clock_update_flags > RQCF_ACT_SKIP)
rf->clock_update_flags = RQCF_UPDATED;
-#endif
+
scx_rq_clock_invalidate(rq);
lockdep_unpin_lock(__rq_lockp(rq), rf->cookie);
}
@@ -1787,12 +1780,10 @@ static inline void rq_repin_lock(struct rq *rq, struct rq_flags *rf)
{
lockdep_repin_lock(__rq_lockp(rq), rf->cookie);

-#ifdef CONFIG_SCHED_DEBUG
/*
* Restore the value we stashed in @rf for this pin context.
*/
rq->clock_update_flags |= rf->clock_update_flags;
-#endif
}

extern
@@ -2066,9 +2057,7 @@ struct sched_group_capacity {
unsigned long next_update;
int imbalance; /* XXX unrelated to capacity but shared group state */

-#ifdef CONFIG_SCHED_DEBUG
int id;
-#endif

unsigned long cpumask[]; /* Balance mask */
};
@@ -2108,13 +2097,8 @@ static inline struct cpumask *group_balance_mask(struct sched_group *sg)

extern int group_balance_cpu(struct sched_group *sg);

-#ifdef CONFIG_SCHED_DEBUG
extern void update_sched_domain_debugfs(void);
extern void dirty_sched_domain_sysctl(int cpu);
-#else
-static inline void update_sched_domain_debugfs(void) { }
-static inline void dirty_sched_domain_sysctl(int cpu) { }
-#endif

extern int sched_update_scaling(void);

@@ -2207,8 +2191,6 @@ enum {

#undef SCHED_FEAT

-#ifdef CONFIG_SCHED_DEBUG
-
/*
* To support run-time toggling of sched features, all the translation units
* (but core.c) reference the sysctl_sched_features defined in core.c.
@@ -2235,24 +2217,6 @@ extern struct static_key sched_feat_keys[__SCHED_FEAT_NR];

#endif /* !CONFIG_JUMP_LABEL */

-#else /* !SCHED_DEBUG: */
-
-/*
- * Each translation unit has its own copy of sysctl_sched_features to allow
- * constants propagation at compile time and compiler optimization based on
- * features default.
- */
-#define SCHED_FEAT(name, enabled) \
- (1UL << __SCHED_FEAT_##name) * enabled |
-static __read_mostly __maybe_unused unsigned int sysctl_sched_features =
-#include "features.h"
- 0;
-#undef SCHED_FEAT
-
-#define sched_feat(x) !!(sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
-
-#endif /* !SCHED_DEBUG */
-
extern struct static_key_false sched_numa_balancing;
extern struct static_key_false sched_schedstats;

@@ -2837,7 +2801,6 @@ extern __read_mostly unsigned int sysctl_sched_migration_cost;

extern unsigned int sysctl_sched_base_slice;

-#ifdef CONFIG_SCHED_DEBUG
extern int sysctl_resched_latency_warn_ms;
extern int sysctl_resched_latency_warn_once;

@@ -2848,7 +2811,6 @@ extern unsigned int sysctl_numa_balancing_scan_period_min;
extern unsigned int sysctl_numa_balancing_scan_period_max;
extern unsigned int sysctl_numa_balancing_scan_size;
extern unsigned int sysctl_numa_balancing_hot_threshold;
-#endif

#ifdef CONFIG_SCHED_HRTICK

@@ -2921,7 +2883,6 @@ unsigned long arch_scale_freq_capacity(int cpu)
}
#endif

-#ifdef CONFIG_SCHED_DEBUG
/*
* In double_lock_balance()/double_rq_lock(), we use raw_spin_rq_lock() to
* acquire rq lock instead of rq_lock(). So at the end of these two functions
@@ -2936,9 +2897,6 @@ static inline void double_rq_clock_clear_update(struct rq *rq1, struct rq *rq2)
rq2->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
#endif
}
-#else
-static inline void double_rq_clock_clear_update(struct rq *rq1, struct rq *rq2) { }
-#endif

#define DEFINE_LOCK_GUARD_2(name, type, _lock, _unlock, ...) \
__DEFINE_UNLOCK_GUARD(name, type, _unlock, type *lock2; __VA_ARGS__) \
@@ -3151,7 +3109,6 @@ extern struct sched_entity *__pick_root_entity(struct cfs_rq *cfs_rq);
extern struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq);
extern struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq);

-#ifdef CONFIG_SCHED_DEBUG
extern bool sched_debug_verbose;

extern void print_cfs_stats(struct seq_file *m, int cpu);
@@ -3162,15 +3119,12 @@ extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq);

extern void resched_latency_warn(int cpu, u64 latency);
-# ifdef CONFIG_NUMA_BALANCING
+#ifdef CONFIG_NUMA_BALANCING
extern void show_numa_stats(struct task_struct *p, struct seq_file *m);
extern void
print_numa_stats(struct seq_file *m, int node, unsigned long tsf,
unsigned long tpf, unsigned long gsf, unsigned long gpf);
-# endif /* CONFIG_NUMA_BALANCING */
-#else /* !CONFIG_SCHED_DEBUG: */
-static inline void resched_latency_warn(int cpu, u64 latency) { }
-#endif /* !CONFIG_SCHED_DEBUG */
+#endif /* CONFIG_NUMA_BALANCING */

extern void init_cfs_rq(struct cfs_rq *cfs_rq);
extern void init_rt_rq(struct rt_rq *rt_rq);
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index c49aea8c1025..cb0769820b0b 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -11,8 +11,6 @@ DEFINE_MUTEX(sched_domains_mutex);
static cpumask_var_t sched_domains_tmpmask;
static cpumask_var_t sched_domains_tmpmask2;

-#ifdef CONFIG_SCHED_DEBUG
-
static int __init sched_debug_setup(char *str)
{
sched_debug_verbose = true;
@@ -151,15 +149,6 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu)
break;
}
}
-#else /* !CONFIG_SCHED_DEBUG */
-
-# define sched_debug_verbose 0
-# define sched_domain_debug(sd, cpu) do { } while (0)
-static inline bool sched_debug(void)
-{
- return false;
-}
-#endif /* CONFIG_SCHED_DEBUG */

/* Generate a mask of SD flags with the SDF_NEEDS_GROUPS metaflag */
#define SD_FLAG(name, mflags) (name * !!((mflags) & SDF_NEEDS_GROUPS)) |
@@ -2275,9 +2264,7 @@ static int __sdt_alloc(const struct cpumask *cpu_map)
if (!sgc)
return -ENOMEM;

-#ifdef CONFIG_SCHED_DEBUG
sgc->id = j;
-#endif

*per_cpu_ptr(sdd->sgc, j) = sgc;
}
--
2.45.2