ftrace: make some tracers reentrant

Now that the ring buffer is reentrant, some of the ftrace tracers
(sched_swich, debugging traces) can also be reentrant.

Note: Never make the function tracer reentrant, that can cause
  recursion problems all over the kernel. The function tracer
  must disable reentrancy.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 8 deletions

diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index c7fa08a5b7f4..b8f56beb1a62 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -24,7 +24,6 @@ probe_sched_switch(struct rq *__rq, struct task_struct *prev,
 {
         struct trace_array_cpu *data;
         unsigned long flags;
-        long disabled;
         int cpu;
         int pc;
 
@@ -41,12 +40,10 @@ probe_sched_switch(struct rq *__rq, struct task_struct *prev,
         local_irq_save(flags);
         cpu = raw_smp_processor_id();
         data = ctx_trace->data[cpu];
-        disabled = atomic_inc_return(&data->disabled);
 
-        if (likely(disabled == 1))
+        if (likely(!atomic_read(&data->disabled)))
                 tracing_sched_switch_trace(ctx_trace, data, prev, next, flags, pc);
 
-        atomic_dec(&data->disabled);
         local_irq_restore(flags);
 }
 
@@ -55,7 +52,6 @@ probe_sched_wakeup(struct rq *__rq, struct task_struct *wakee)
 {
         struct trace_array_cpu *data;
         unsigned long flags;
-        long disabled;
         int cpu, pc;
 
         if (!likely(tracer_enabled))
@@ -67,13 +63,11 @@ probe_sched_wakeup(struct rq *__rq, struct task_struct *wakee)
         local_irq_save(flags);
         cpu = raw_smp_processor_id();
         data = ctx_trace->data[cpu];
-        disabled = atomic_inc_return(&data->disabled);
 
-        if (likely(disabled == 1))
+        if (likely(!atomic_read(&data->disabled)))
                 tracing_sched_wakeup_trace(ctx_trace, data, wakee, current,
                                            flags, pc);
 
-        atomic_dec(&data->disabled);
         local_irq_restore(flags);
 }