powerpc64/ftrace: Disable ftrace during hotplug

Disable ftrace when a cpu is about to go offline. When the cpu is woken
up, ftrace will get enabled in start_secondary().

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/smp.c

@@ -1166,6 +1166,8 @@ int __cpu_disable(void)
 	if (!smp_ops->cpu_disable)
 		return -ENOSYS;
 
+	this_cpu_disable_ftrace();
+
 	err = smp_ops->cpu_disable();
 	if (err)
 		return err;
@@ -1184,6 +1186,12 @@ void __cpu_die(unsigned int cpu)
 
 void cpu_die(void)
 {
+	/*
+	 * Disable on the down path. This will be re-enabled by
+	 * start_secondary() via start_secondary_resume() below
+	 */
+	this_cpu_disable_ftrace();
+
 	if (ppc_md.cpu_die)
 		ppc_md.cpu_die();