ftrace: irqsoff use raw_smp_processor_id

This patch changes the use of __get_cpu_var to explicitly calling
raw_smp_processor_id and using the per_cpu() macro. On some debug
configurations, the use of __get_cpu_var may cause ftrace to trigger
and this can cause problems with the irqsoff tracing.

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

1 files changed, 10 insertions, 9 deletions

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index d0c1748b1e2c..761f3ec66c50 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -204,14 +204,14 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip)
         if (likely(!tracer_enabled))
                 return;
 
-        if (__get_cpu_var(tracing_cpu))
+        cpu = raw_smp_processor_id();
+
+        if (per_cpu(tracing_cpu, cpu))
                 return;
 
-        cpu = raw_smp_processor_id();
         data = tr->data[cpu];
 
-        if (unlikely(!data) || unlikely(!head_page(data)) ||
-            atomic_read(&data->disabled))
+        if (unlikely(!data) || atomic_read(&data->disabled))
                 return;
 
         atomic_inc(&data->disabled);
@@ -225,7 +225,7 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip)
 
         trace_function(tr, data, ip, parent_ip, flags);
 
-        __get_cpu_var(tracing_cpu) = 1;
+        per_cpu(tracing_cpu, cpu) = 1;
 
         atomic_dec(&data->disabled);
 }
@@ -238,16 +238,16 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip)
         struct trace_array_cpu *data;
         unsigned long flags;
 
+        cpu = raw_smp_processor_id();
         /* Always clear the tracing cpu on stopping the trace */
-        if (unlikely(__get_cpu_var(tracing_cpu)))
-                __get_cpu_var(tracing_cpu) = 0;
+        if (unlikely(per_cpu(tracing_cpu, cpu)))
+                per_cpu(tracing_cpu, cpu) = 0;
         else
                 return;
 
         if (!tracer_enabled)
                 return;
 
-        cpu = raw_smp_processor_id();
         data = tr->data[cpu];
 
         if (unlikely(!data) || unlikely(!head_page(data)) ||
@@ -255,6 +255,7 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip)
                 return;
 
         atomic_inc(&data->disabled);
+
         local_save_flags(flags);
         trace_function(tr, data, ip, parent_ip, flags);
         check_critical_timing(tr, data, parent_ip ? : ip, cpu);
@@ -376,7 +377,7 @@ static void stop_irqsoff_tracer(struct trace_array *tr)
 static void __irqsoff_tracer_init(struct trace_array *tr)
 {
         irqsoff_trace = tr;
-        /* make sure that the tracer is visibel */
+        /* make sure that the tracer is visible */
         smp_wmb();
 
         if (tr->ctrl)