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: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
index e555ab6..3b4dc09 100644 (file)
--- a/lib/smp_processor_id.c
+++ b/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;
 }