sched/core: Skip sched_core_fork/free() when core sched is disabled

As __put_task_struct() and copy_process() are hot path functions,
the call of sched_core_fork/free() will bring overhead when core
sched is disabled, and we skip them when core sched is disabled().

Signed-off-by: Cruz Zhao <CruzZhao@linux.alibaba.com>

include/linux/sched.h

@@ -2397,9 +2397,19 @@ extern void sched_core_free(struct task_struct *tsk);
 extern void sched_core_fork(struct task_struct *p);
 extern int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type,
 				unsigned long uaddr);
+DECLARE_STATIC_KEY_FALSE(__sched_core_enabled);
+static inline bool sched_core_disabled(void)
+{
+	return !static_branch_unlikely(&__sched_core_enabled);
+}
+
 #else
 static inline void sched_core_free(struct task_struct *tsk) { }
 static inline void sched_core_fork(struct task_struct *p) { }
+static inline bool sched_core_disabled(void)
+{
+	return true;
+}
 #endif
 
 #endif

kernel/fork.c

@@ -845,7 +845,8 @@ void __put_task_struct(struct task_struct *tsk)
 	exit_creds(tsk);
 	delayacct_tsk_free(tsk);
 	put_signal_struct(tsk->signal);
-	sched_core_free(tsk);
+	if (!sched_core_disabled())
+		sched_core_free(tsk);
 	free_task(tsk);
 }
 EXPORT_SYMBOL_GPL(__put_task_struct);
@@ -2383,7 +2384,8 @@ static __latent_entropy struct task_struct *copy_process(
 
 	klp_copy_process(p);
 
-	sched_core_fork(p);
+	if (!sched_core_disabled())
+		sched_core_fork(p);
 
 	spin_lock(&current->sighand->siglock);
 
@@ -2471,7 +2473,8 @@ static __latent_entropy struct task_struct *copy_process(
 	return p;
 
 bad_fork_cancel_cgroup:
-	sched_core_free(p);
+	if (!sched_core_disabled())
+		sched_core_free(p);
 	spin_unlock(&current->sighand->siglock);
 	write_unlock_irq(&tasklist_lock);
 	cgroup_cancel_fork(p, args);

kernel/sched/sched.h

@@ -1150,11 +1150,6 @@ static inline bool sched_core_enabled(struct rq *rq)
 	return static_branch_unlikely(&__sched_core_enabled) && rq->core_enabled;
 }
 
-static inline bool sched_core_disabled(void)
-{
-	return !static_branch_unlikely(&__sched_core_enabled);
-}
-
 /*
  * Be careful with this function; not for general use. The return value isn't
  * stable unless you actually hold a relevant rq->__lock.
@@ -1252,11 +1247,6 @@ static inline bool sched_core_enabled(struct rq *rq)
 	return false;
 }
 
-static inline bool sched_core_disabled(void)
-{
-	return true;
-}
-
 static inline raw_spinlock_t *rq_lockp(struct rq *rq)
 {
 	return &rq->__lock;