ftrace: debug smp_processor_id, use notrace preempt disable

The debug smp_processor_id caused a recursive fault in debugging
the irqsoff tracer. The tracer used a smp_processor_id in the
ftrace callback, and this function called preempt_disable which
also is traced. This caused a recursive fault (stack overload).

Since using smp_processor_id without debugging on does not cause
faults with the tracer (even when the tracer is wrong), the
debug version should not cause a system reboot.

This changes the debug_smp_processor_id to use the notrace versions
of preempt_disable and enable.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

lib/smp_processor_id.c

@@ -37,7 +37,7 @@ notrace unsigned int debug_smp_processor_id(void)
 	/*
 	 * Avoid recursion:
 	 */
-	preempt_disable();
+	preempt_disable_notrace();
 
 	if (!printk_ratelimit())
 		goto out_enable;
@@ -49,7 +49,7 @@ notrace unsigned int debug_smp_processor_id(void)
 	dump_stack();
 
 out_enable:
-	preempt_enable_no_resched();
+	preempt_enable_no_resched_notrace();
 out:
 	return this_cpu;
 }