preempt: Use preempt_schedule_context() as the official tracing preemption point

preempt_schedule_context() is a tracing safe preemption point but it's
only used when CONFIG_CONTEXT_TRACKING=y. Other configs have tracing
recursion issues since commit:

b30f0e3ffedf ("sched/preempt: Optimize preemption operations on __schedule() callers")

introduced function based preemp_count_*() ops.

Lets make it available on all configs and give it a more appropriate
name for its new position.

Reported-by: Fengguang Wu <[e-mail]>
Signed-off-by: Frederic Weisbecker <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/include/asm/preempt.h

···
   extern asmlinkage void ___preempt_schedule(void);
 # define __preempt_schedule() asm ("call ___preempt_schedule")
   extern asmlinkage void preempt_schedule(void);
-# ifdef CONFIG_CONTEXT_TRACKING
-    extern asmlinkage void ___preempt_schedule_context(void);
-#   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
-    extern asmlinkage void preempt_schedule_context(void);
-# endif
+  extern asmlinkage void ___preempt_schedule_notrace(void);
+# define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
+  extern asmlinkage void preempt_schedule_notrace(void);
 #endif
 
 #endif /* __ASM_PREEMPT_H */

arch/x86/kernel/i386_ksyms_32.c

···
 
 #ifdef CONFIG_PREEMPT
 EXPORT_SYMBOL(___preempt_schedule);
-#ifdef CONFIG_CONTEXT_TRACKING
-EXPORT_SYMBOL(___preempt_schedule_context);
-#endif
+EXPORT_SYMBOL(___preempt_schedule_notrace);
 #endif

arch/x86/kernel/x8664_ksyms_64.c

···
 
 #ifdef CONFIG_PREEMPT
 EXPORT_SYMBOL(___preempt_schedule);
-#ifdef CONFIG_CONTEXT_TRACKING
-EXPORT_SYMBOL(___preempt_schedule_context);
-#endif
+EXPORT_SYMBOL(___preempt_schedule_notrace);
 #endif

arch/x86/lib/thunk_32.S

···
 
 #ifdef CONFIG_PREEMPT
 	THUNK ___preempt_schedule, preempt_schedule
-#ifdef CONFIG_CONTEXT_TRACKING
-	THUNK ___preempt_schedule_context, preempt_schedule_context
-#endif
+	THUNK ___preempt_schedule_notrace, preempt_schedule_notrace
 #endif
 

arch/x86/lib/thunk_64.S

···
 
 #ifdef CONFIG_PREEMPT
 	THUNK ___preempt_schedule, preempt_schedule
-#ifdef CONFIG_CONTEXT_TRACKING
-	THUNK ___preempt_schedule_context, preempt_schedule_context
-#endif
+	THUNK ___preempt_schedule_notrace, preempt_schedule_notrace
 #endif
 
 #if defined(CONFIG_TRACE_IRQFLAGS) \

include/asm-generic/preempt.h

···
 #ifdef CONFIG_PREEMPT
 extern asmlinkage void preempt_schedule(void);
 #define __preempt_schedule() preempt_schedule()
-
-#ifdef CONFIG_CONTEXT_TRACKING
-extern asmlinkage void preempt_schedule_context(void);
-#define __preempt_schedule_context() preempt_schedule_context()
-#endif
+extern asmlinkage void preempt_schedule_notrace(void);
+#define __preempt_schedule_notrace() preempt_schedule_notrace()
 #endif /* CONFIG_PREEMPT */
 
 #endif /* __ASM_PREEMPT_H */

include/linux/preempt.h

···
 
 #ifdef CONFIG_PREEMPT
 
-#ifndef CONFIG_CONTEXT_TRACKING
-#define __preempt_schedule_context() __preempt_schedule()
-#endif
-
 #define preempt_enable_notrace() \
 do { \
 	barrier(); \
 	if (unlikely(__preempt_count_dec_and_test())) \
-		__preempt_schedule_context(); \
+		__preempt_schedule_notrace(); \
 } while (0)
 #else
 #define preempt_enable_notrace() \

kernel/sched/core.c

···
 NOKPROBE_SYMBOL(preempt_schedule);
 EXPORT_SYMBOL(preempt_schedule);
 
-#ifdef CONFIG_CONTEXT_TRACKING
 /**
- * preempt_schedule_context - preempt_schedule called by tracing
+ * preempt_schedule_notrace - preempt_schedule called by tracing
  *
  * The tracing infrastructure uses preempt_enable_notrace to prevent
  * recursion and tracing preempt enabling caused by the tracing
···
  * instead of preempt_schedule() to exit user context if needed before
  * calling the scheduler.
  */
-asmlinkage __visible void __sched notrace preempt_schedule_context(void)
+asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
 {
 	enum ctx_state prev_ctx;
 
···
 		__preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
 	} while (need_resched());
 }
-EXPORT_SYMBOL_GPL(preempt_schedule_context);
-#endif /* CONFIG_CONTEXT_TRACKING */
+EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
 
 #endif /* CONFIG_PREEMPT */