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Subject[PATCH 7/9] tracing: Use one prologue for the wakeup tracer function tracers
From: Steven Rostedt <srostedt@redhat.com>

The wakeup tracer has three types of function tracers. Normal
function tracer, function graph entry, and function graph return.
Each of these use a complex dance to prevent recursion and whether
to trace the data or not (depending on the wake_task variable).

This patch moves the duplicate code into a single routine, to
prevent future mistakes with modifying duplicate complex code.

Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_sched_wakeup.c | 102 ++++++++++++++++++-------------------
1 files changed, 50 insertions(+), 52 deletions(-)
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 033510d..31689d2 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -56,43 +56,73 @@ static struct tracer_flags tracer_flags = {
#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)

#ifdef CONFIG_FUNCTION_TRACER
+
/*
- * wakeup uses its own tracer function to keep the overhead down:
+ * Prologue for the wakeup function tracers.
+ *
+ * Returns 1 if it is OK to continue, and preemption
+ * is disabled and data->disabled is incremented.
+ * 0 if the trace is to be ignored, and preemption
+ * is not disabled and data->disabled is
+ * kept the same.
+ *
+ * Note, this function is also used outside this ifdef but
+ * inside the #ifdef of the function graph tracer below.
+ * This is OK, since the function graph tracer is
+ * dependent on the function tracer.
*/
-static void
-wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
+static int
+func_prolog_preempt_disable(struct trace_array *tr,
+ struct trace_array_cpu **data,
+ int *pc)
{
- struct trace_array *tr = wakeup_trace;
- struct trace_array_cpu *data;
- unsigned long flags;
long disabled;
int cpu;
- int pc;

if (likely(!wakeup_task))
- return;
+ return 0;

- pc = preempt_count();
+ *pc = preempt_count();
preempt_disable_notrace();

cpu = raw_smp_processor_id();
if (cpu != wakeup_current_cpu)
goto out_enable;

- data = tr->data[cpu];
- disabled = atomic_inc_return(&data->disabled);
+ *data = tr->data[cpu];
+ disabled = atomic_inc_return(&(*data)->disabled);
if (unlikely(disabled != 1))
goto out;

- local_irq_save(flags);
+ return 1;

- trace_function(tr, ip, parent_ip, flags, pc);
+out:
+ atomic_dec(&(*data)->disabled);
+
+out_enable:
+ preempt_enable_notrace();
+ return 0;
+}
+
+/*
+ * wakeup uses its own tracer function to keep the overhead down:
+ */
+static void
+wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
+{
+ struct trace_array *tr = wakeup_trace;
+ struct trace_array_cpu *data;
+ unsigned long flags;
+ int pc;
+
+ if (!func_prolog_preempt_disable(tr, &data, &pc))
+ return;

+ local_irq_save(flags);
+ trace_function(tr, ip, parent_ip, flags, pc);
local_irq_restore(flags);

- out:
atomic_dec(&data->disabled);
- out_enable:
preempt_enable_notrace();
}

@@ -154,32 +184,16 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
struct trace_array *tr = wakeup_trace;
struct trace_array_cpu *data;
unsigned long flags;
- long disabled;
- int cpu, pc, ret = 0;
+ int pc, ret = 0;

- if (likely(!wakeup_task))
+ if (!func_prolog_preempt_disable(tr, &data, &pc))
return 0;

- pc = preempt_count();
- preempt_disable_notrace();
-
- cpu = raw_smp_processor_id();
- if (cpu != wakeup_current_cpu)
- goto out_enable;
-
- data = tr->data[cpu];
- disabled = atomic_inc_return(&data->disabled);
- if (unlikely(disabled != 1))
- goto out;
-
local_save_flags(flags);
ret = __trace_graph_entry(tr, trace, flags, pc);
-
-out:
atomic_dec(&data->disabled);
-
-out_enable:
preempt_enable_notrace();
+
return ret;
}

@@ -188,31 +202,15 @@ static void wakeup_graph_return(struct ftrace_graph_ret *trace)
struct trace_array *tr = wakeup_trace;
struct trace_array_cpu *data;
unsigned long flags;
- long disabled;
- int cpu, pc;
+ int pc;

- if (likely(!wakeup_task))
+ if (!func_prolog_preempt_disable(tr, &data, &pc))
return;

- pc = preempt_count();
- preempt_disable_notrace();
-
- cpu = raw_smp_processor_id();
- if (cpu != wakeup_current_cpu)
- goto out_enable;
-
- data = tr->data[cpu];
- disabled = atomic_inc_return(&data->disabled);
- if (unlikely(disabled != 1))
- goto out;
-
local_save_flags(flags);
__trace_graph_return(tr, trace, flags, pc);
-
-out:
atomic_dec(&data->disabled);

-out_enable:
preempt_enable_notrace();
return;
}
--
1.7.1



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