sched/preempt: Use CONFIG_PREEMPTION where appropriate

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by
CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same
functionality which today depends on CONFIG_PREEMPT.

Switch the preemption code, scheduler and init task over to use
CONFIG_PREEMPTION.

That's the first step towards RT in that area. The more complex changes are
coming separately.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20190726212124.117528401@linutronix.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

include/asm-generic/preempt.h

@@ -78,11 +78,11 @@ static __always_inline bool should_resched(int preempt_offset)
 			tif_need_resched());
 }
 
-#ifdef CONFIG_PREEMPT
+#ifdef CONFIG_PREEMPTION
 extern asmlinkage void preempt_schedule(void);
 #define __preempt_schedule() preempt_schedule()
 extern asmlinkage void preempt_schedule_notrace(void);
 #define __preempt_schedule_notrace() preempt_schedule_notrace()
-#endif /* CONFIG_PREEMPT */
+#endif /* CONFIG_PREEMPTION */
 
 #endif /* __ASM_PREEMPT_H */

include/linux/preempt.h

@@ -182,7 +182,7 @@ do { \
 
 #define preemptible()	(preempt_count() == 0 && !irqs_disabled())
 
-#ifdef CONFIG_PREEMPT
+#ifdef CONFIG_PREEMPTION
 #define preempt_enable() \
 do { \
 	barrier(); \
@@ -203,7 +203,7 @@ do { \
 		__preempt_schedule(); \
 } while (0)
 
-#else /* !CONFIG_PREEMPT */
+#else /* !CONFIG_PREEMPTION */
 #define preempt_enable() \
 do { \
 	barrier(); \
@@ -217,7 +217,7 @@ do { \
 } while (0)
 
 #define preempt_check_resched() do { } while (0)
-#endif /* CONFIG_PREEMPT */
+#endif /* CONFIG_PREEMPTION */
 
 #define preempt_disable_notrace() \
 do { \

include/linux/sched.h

@@ -1767,7 +1767,7 @@ static inline int test_tsk_need_resched(struct task_struct *tsk)
  * value indicates whether a reschedule was done in fact.
  * cond_resched_lock() will drop the spinlock before scheduling,
  */
-#ifndef CONFIG_PREEMPT
+#ifndef CONFIG_PREEMPTION
 extern int _cond_resched(void);
 #else
 static inline int _cond_resched(void) { return 0; }
@@ -1796,12 +1796,12 @@ static inline void cond_resched_rcu(void)
 
 /*
  * Does a critical section need to be broken due to another
- * task waiting?: (technically does not depend on CONFIG_PREEMPT,
+ * task waiting?: (technically does not depend on CONFIG_PREEMPTION,
  * but a general need for low latency)
  */
 static inline int spin_needbreak(spinlock_t *lock)
 {
-#ifdef CONFIG_PREEMPT
+#ifdef CONFIG_PREEMPTION
 	return spin_is_contended(lock);
 #else
 	return 0;

init/init_task.c

@@ -174,7 +174,7 @@ struct task_struct init_task
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	.ret_stack	= NULL,
 #endif
-#if defined(CONFIG_TRACING) && defined(CONFIG_PREEMPT)
+#if defined(CONFIG_TRACING) && defined(CONFIG_PREEMPTION)
 	.trace_recursion = 0,
 #endif
 #ifdef CONFIG_LIVEPATCH

init/main.c

@@ -433,7 +433,7 @@ noinline void __ref rest_init(void)
 
 	/*
 	 * Enable might_sleep() and smp_processor_id() checks.
-	 * They cannot be enabled earlier because with CONFIG_PREEMPT=y
+	 * They cannot be enabled earlier because with CONFIG_PREEMPTION=y
 	 * kernel_thread() would trigger might_sleep() splats. With
 	 * CONFIG_PREEMPT_VOLUNTARY=y the init task might have scheduled
 	 * already, but it's stuck on the kthreadd_done completion.

kernel/sched/core.c

@@ -3581,7 +3581,7 @@ static inline void sched_tick_start(int cpu) { }
 static inline void sched_tick_stop(int cpu) { }
 #endif
 
-#if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
+#if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
 				defined(CONFIG_TRACE_PREEMPT_TOGGLE))
 /*
  * If the value passed in is equal to the current preempt count
@@ -3782,7 +3782,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
  *      task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
  *      called on the nearest possible occasion:
  *
- *       - If the kernel is preemptible (CONFIG_PREEMPT=y):
+ *       - If the kernel is preemptible (CONFIG_PREEMPTION=y):
  *
  *         - in syscall or exception context, at the next outmost
  *           preempt_enable(). (this might be as soon as the wake_up()'s
@@ -3791,7 +3791,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
  *         - in IRQ context, return from interrupt-handler to
  *           preemptible context
  *
- *       - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
+ *       - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
  *         then at the next:
  *
  *          - cond_resched() call
@@ -4033,7 +4033,7 @@ static void __sched notrace preempt_schedule_common(void)
 	} while (need_resched());
 }
 
-#ifdef CONFIG_PREEMPT
+#ifdef CONFIG_PREEMPTION
 /*
  * this is the entry point to schedule() from in-kernel preemption
  * off of preempt_enable. Kernel preemptions off return from interrupt
@@ -4105,7 +4105,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
 }
 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
 
-#endif /* CONFIG_PREEMPT */
+#endif /* CONFIG_PREEMPTION */
 
 /*
  * this is the entry point to schedule() from kernel preemption
@@ -5416,7 +5416,7 @@ SYSCALL_DEFINE0(sched_yield)
 	return 0;
 }
 
-#ifndef CONFIG_PREEMPT
+#ifndef CONFIG_PREEMPTION
 int __sched _cond_resched(void)
 {
 	if (should_resched(0)) {
@@ -5433,7 +5433,7 @@ EXPORT_SYMBOL(_cond_resched);
  * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
  * call schedule, and on return reacquire the lock.
  *
- * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
+ * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
  * operations here to prevent schedule() from being called twice (once via
  * spin_unlock(), once by hand).
  */

kernel/sched/fair.c

@@ -7430,7 +7430,7 @@ static int detach_tasks(struct lb_env *env)
 		detached++;
 		env->imbalance -= load;
 
-#ifdef CONFIG_PREEMPT
+#ifdef CONFIG_PREEMPTION
 		/*
 		 * NEWIDLE balancing is a source of latency, so preemptible
 		 * kernels will stop after the first task is detached to minimize

kernel/sched/sched.h

@@ -1943,7 +1943,7 @@ unsigned long arch_scale_freq_capacity(int cpu)
 #endif
 
 #ifdef CONFIG_SMP
-#ifdef CONFIG_PREEMPT
+#ifdef CONFIG_PREEMPTION
 
 static inline void double_rq_lock(struct rq *rq1, struct rq *rq2);
 
@@ -1995,7 +1995,7 @@ static inline int _double_lock_balance(struct rq *this_rq, struct rq *busiest)
 	return ret;
 }
 
-#endif /* CONFIG_PREEMPT */
+#endif /* CONFIG_PREEMPTION */
 
 /*
  * double_lock_balance - lock the busiest runqueue, this_rq is locked already.