sched/debug: Make 'const_debug' tunables unconditional __read_mostly

With CONFIG_SCHED_DEBUG becoming unconditional, remove the
extra 'const_debug' indirection towards __read_mostly.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250317104257.3496611-3-mingo@kernel.org

Author: Ingo Molnar

kernel/sched/core.c

@@ -128,7 +128,7 @@ DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
  */
 #define SCHED_FEAT(name, enabled)	\
 	(1UL << __SCHED_FEAT_##name) * enabled |
-const_debug unsigned int sysctl_sched_features =
+__read_mostly unsigned int sysctl_sched_features =
 #include "features.h"
 	0;
 #undef SCHED_FEAT
@@ -148,7 +148,7 @@ __read_mostly int sysctl_resched_latency_warn_once = 1;
  * Number of tasks to iterate in a single balance run.
  * Limited because this is done with IRQs disabled.
  */
-const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;
+__read_mostly unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;
 
 __read_mostly int scheduler_running;
 

kernel/sched/fair.c

@@ -79,7 +79,7 @@ unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
 unsigned int sysctl_sched_base_slice			= 700000ULL;
 static unsigned int normalized_sysctl_sched_base_slice	= 700000ULL;
 
-const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
+__read_mostly unsigned int sysctl_sched_migration_cost	= 500000UL;
 
 static int __init setup_sched_thermal_decay_shift(char *str)
 {

kernel/sched/sched.h

@@ -2194,13 +2194,8 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
 }
 
 /*
- * Tunables that become constants when CONFIG_SCHED_DEBUG is off:
+ * Tunables:
  */
-#ifdef CONFIG_SCHED_DEBUG
-# define const_debug __read_mostly
-#else
-# define const_debug const
-#endif
 
 #define SCHED_FEAT(name, enabled)	\
 	__SCHED_FEAT_##name ,
@@ -2218,7 +2213,7 @@ enum {
  * To support run-time toggling of sched features, all the translation units
  * (but core.c) reference the sysctl_sched_features defined in core.c.
  */
-extern const_debug unsigned int sysctl_sched_features;
+extern __read_mostly unsigned int sysctl_sched_features;
 
 #ifdef CONFIG_JUMP_LABEL
 
@@ -2249,7 +2244,7 @@ extern struct static_key sched_feat_keys[__SCHED_FEAT_NR];
  */
 #define SCHED_FEAT(name, enabled)	\
 	(1UL << __SCHED_FEAT_##name) * enabled |
-static const_debug __maybe_unused unsigned int sysctl_sched_features =
+static __read_mostly __maybe_unused unsigned int sysctl_sched_features =
 #include "features.h"
 	0;
 #undef SCHED_FEAT
@@ -2837,8 +2832,8 @@ extern void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags);
 # define SCHED_NR_MIGRATE_BREAK 32
 #endif
 
-extern const_debug unsigned int sysctl_sched_nr_migrate;
-extern const_debug unsigned int sysctl_sched_migration_cost;
+extern __read_mostly unsigned int sysctl_sched_nr_migrate;
+extern __read_mostly unsigned int sysctl_sched_migration_cost;
 
 extern unsigned int sysctl_sched_base_slice;