MIPS: Fix kernel hang under FUNCTION_GRAPH_TRACER and PREEMPT_TRACER

When update the latest mainline kernel with the following three configs,
the kernel hangs during startup:

(1) CONFIG_FUNCTION_GRAPH_TRACER=y
(2) CONFIG_PREEMPT_TRACER=y
(3) CONFIG_FTRACE_STARTUP_TEST=y

When update the latest mainline kernel with the above two configs (1)
and (2), the kernel starts normally, but it still hangs when execute
the following command:

echo "function_graph" > /sys/kernel/debug/tracing/current_tracer

Without CONFIG_PREEMPT_TRACER=y, the above two kinds of kernel hangs
disappeared, so it seems that CONFIG_PREEMPT_TRACER has some influences
with function_graph tracer at the first glance.

I use ejtag to find out the epc address is related with preempt_enable()
in the file arch/mips/lib/mips-atomic.c, because function tracing can
trace the preempt_{enable,disable} calls that are traced, replace them
with preempt_{enable,disable}_notrace to prevent function tracing from
going into an infinite loop, and then it can fix the kernel hang issue.

By the way, it seems that this commit is a complement and improvement of
commit f93a1a00f2bd ("MIPS: Fix crash that occurs when function tracing
is enabled").

Signed-off-by: Tiezhu Yang <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/lib/mips-atomic.c

···
  */
 notrace void arch_local_irq_disable(void)
 {
-	preempt_disable();
+	preempt_disable_notrace();
 
 	__asm__ __volatile__(
 	"	.set	push						\n"
···
 	: /* no inputs */
 	: "memory");
 
-	preempt_enable();
+	preempt_enable_notrace();
 }
 EXPORT_SYMBOL(arch_local_irq_disable);
 
···
 {
 	unsigned long flags;
 
-	preempt_disable();
+	preempt_disable_notrace();
 
 	__asm__ __volatile__(
 	"	.set	push						\n"
···
 	: /* no inputs */
 	: "memory");
 
-	preempt_enable();
+	preempt_enable_notrace();
 
 	return flags;
 }
···
 {
 	unsigned long __tmp1;
 
-	preempt_disable();
+	preempt_disable_notrace();
 
 	__asm__ __volatile__(
 	"	.set	push						\n"
···
 	: "0" (flags)
 	: "memory");
 
-	preempt_enable();
+	preempt_enable_notrace();
 }
 EXPORT_SYMBOL(arch_local_irq_restore);