sched/preempt: Take away preempt_enable_no_resched() from modules

Discourage drivers/modules to be creative with preemption.

Sadly all is implemented in macros and inline so if they want to do
evil they still can, but at least try and discourage some.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Cc: rui.zhang@intel.com
Cc: jacob.jun.pan@linux.intel.com
Cc: Mike Galbraith <bitbucket@online.de>
Cc: hpa@zytor.com
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: lenb@kernel.org
Cc: rjw@rjwysocki.net
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-fn7h6vu8wtgxk0ih402qcijx@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/uaccess.h

@@ -25,13 +25,16 @@ static inline void pagefault_disable(void)
 
 static inline void pagefault_enable(void)
 {
+#ifndef CONFIG_PREEMPT
 	/*
 	 * make sure to issue those last loads/stores before enabling
 	 * the pagefault handler again.
 	 */
 	barrier();
 	preempt_count_dec();
-	preempt_check_resched();
+#else
+	preempt_enable();
+#endif
 }
 
 #ifndef ARCH_HAS_NOCACHE_UACCESS