tracing: Use one prologue for the preempt irqs off tracer function tracers
authorSteven Rostedt <srostedt@redhat.com>
Tue, 5 Oct 2010 23:41:43 +0000 (19:41 -0400)
committerSteven Rostedt <rostedt@goodmis.org>
Mon, 18 Oct 2010 14:53:36 +0000 (10:53 -0400)
The preempt and irqsoff tracers have 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 if interrupts are enabled or not).

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_irqsoff.c

index 4047e98afcbaeac84c744be078d451c75f47b9d3..5cf8c602b8804c054bbed65475b4815fd29d5b82 100644 (file)
@@ -87,14 +87,22 @@ static __cacheline_aligned_in_smp   unsigned long max_sequence;
 
 #ifdef CONFIG_FUNCTION_TRACER
 /*
- * irqsoff uses its own tracer function to keep the overhead down:
+ * Prologue for the preempt and irqs off function tracers.
+ *
+ * Returns 1 if it is OK to continue, and data->disabled is
+ *            incremented.
+ *         0 if the trace is to be ignored, 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
-irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
+static int func_prolog_dec(struct trace_array *tr,
+                          struct trace_array_cpu **data,
+                          unsigned long *flags)
 {
-       struct trace_array *tr = irqsoff_trace;
-       struct trace_array_cpu *data;
-       unsigned long flags;
        long disabled;
        int cpu;
 
@@ -106,18 +114,38 @@ irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
         */
        cpu = raw_smp_processor_id();
        if (likely(!per_cpu(tracing_cpu, cpu)))
-               return;
+               return 0;
 
-       local_save_flags(flags);
+       local_save_flags(*flags);
        /* slight chance to get a false positive on tracing_cpu */
-       if (!irqs_disabled_flags(flags))
-               return;
+       if (!irqs_disabled_flags(*flags))
+               return 0;
 
-       data = tr->data[cpu];
-       disabled = atomic_inc_return(&data->disabled);
+       *data = tr->data[cpu];
+       disabled = atomic_inc_return(&(*data)->disabled);
 
        if (likely(disabled == 1))
-               trace_function(tr, ip, parent_ip, flags, preempt_count());
+               return 1;
+
+       atomic_dec(&(*data)->disabled);
+
+       return 0;
+}
+
+/*
+ * irqsoff uses its own tracer function to keep the overhead down:
+ */
+static void
+irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
+{
+       struct trace_array *tr = irqsoff_trace;
+       struct trace_array_cpu *data;
+       unsigned long flags;
+
+       if (!func_prolog_dec(tr, &data, &flags))
+               return;
+
+       trace_function(tr, ip, parent_ip, flags, preempt_count());
 
        atomic_dec(&data->disabled);
 }
@@ -155,30 +183,16 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
        struct trace_array *tr = irqsoff_trace;
        struct trace_array_cpu *data;
        unsigned long flags;
-       long disabled;
        int ret;
-       int cpu;
        int pc;
 
-       cpu = raw_smp_processor_id();
-       if (likely(!per_cpu(tracing_cpu, cpu)))
-               return 0;
-
-       local_save_flags(flags);
-       /* slight chance to get a false positive on tracing_cpu */
-       if (!irqs_disabled_flags(flags))
+       if (!func_prolog_dec(tr, &data, &flags))
                return 0;
 
-       data = tr->data[cpu];
-       disabled = atomic_inc_return(&data->disabled);
-
-       if (likely(disabled == 1)) {
-               pc = preempt_count();
-               ret = __trace_graph_entry(tr, trace, flags, pc);
-       } else
-               ret = 0;
-
+       pc = preempt_count();
+       ret = __trace_graph_entry(tr, trace, flags, pc);
        atomic_dec(&data->disabled);
+
        return ret;
 }
 
@@ -187,27 +201,13 @@ static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
        struct trace_array *tr = irqsoff_trace;
        struct trace_array_cpu *data;
        unsigned long flags;
-       long disabled;
-       int cpu;
        int pc;
 
-       cpu = raw_smp_processor_id();
-       if (likely(!per_cpu(tracing_cpu, cpu)))
-               return;
-
-       local_save_flags(flags);
-       /* slight chance to get a false positive on tracing_cpu */
-       if (!irqs_disabled_flags(flags))
+       if (!func_prolog_dec(tr, &data, &flags))
                return;
 
-       data = tr->data[cpu];
-       disabled = atomic_inc_return(&data->disabled);
-
-       if (likely(disabled == 1)) {
-               pc = preempt_count();
-               __trace_graph_return(tr, trace, flags, pc);
-       }
-
+       pc = preempt_count();
+       __trace_graph_return(tr, trace, flags, pc);
        atomic_dec(&data->disabled);
 }