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Subject[PATCH 6/9] tracing: Graph support for wakeup tracer
From: Jiri Olsa <jolsa@redhat.com>

Add function graph support for wakeup latency tracer.
The graph output is enabled by setting the 'display-graph'
trace option.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
LKML-Reference: <1285243253-7372-4-git-send-email-jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_sched_wakeup.c | 231 +++++++++++++++++++++++++++++++++++--
1 files changed, 221 insertions(+), 10 deletions(-)
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 4086eae..033510d 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -31,13 +31,33 @@ static int wakeup_rt;
static arch_spinlock_t wakeup_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;

+static void wakeup_reset(struct trace_array *tr);
static void __wakeup_reset(struct trace_array *tr);
+static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
+static void wakeup_graph_return(struct ftrace_graph_ret *trace);

static int save_lat_flag;

+#define TRACE_DISPLAY_GRAPH 1
+
+static struct tracer_opt trace_opts[] = {
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ /* display latency trace as call graph */
+ { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
+#endif
+ { } /* Empty entry */
+};
+
+static struct tracer_flags tracer_flags = {
+ .val = 0,
+ .opts = trace_opts,
+};
+
+#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
+
#ifdef CONFIG_FUNCTION_TRACER
/*
- * irqsoff uses its own tracer function to keep the overhead down:
+ * wakeup uses its own tracer function to keep the overhead down:
*/
static void
wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
@@ -80,8 +100,191 @@ static struct ftrace_ops trace_ops __read_mostly =
{
.func = wakeup_tracer_call,
};
+
+static int start_func_tracer(int graph)
+{
+ int ret;
+
+ if (!graph)
+ ret = register_ftrace_function(&trace_ops);
+ else
+ ret = register_ftrace_graph(&wakeup_graph_return,
+ &wakeup_graph_entry);
+
+ if (!ret && tracing_is_enabled())
+ tracer_enabled = 1;
+ else
+ tracer_enabled = 0;
+
+ return ret;
+}
+
+static void stop_func_tracer(int graph)
+{
+ tracer_enabled = 0;
+
+ if (!graph)
+ unregister_ftrace_function(&trace_ops);
+ else
+ unregister_ftrace_graph();
+}
+
#endif /* CONFIG_FUNCTION_TRACER */

+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
+{
+
+ if (!(bit & TRACE_DISPLAY_GRAPH))
+ return -EINVAL;
+
+ if (!(is_graph() ^ set))
+ return 0;
+
+ stop_func_tracer(!set);
+
+ wakeup_reset(wakeup_trace);
+ tracing_max_latency = 0;
+
+ return start_func_tracer(set);
+}
+
+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;
+
+ if (likely(!wakeup_task))
+ 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;
+}
+
+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;
+
+ if (likely(!wakeup_task))
+ 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;
+}
+
+static void wakeup_trace_open(struct trace_iterator *iter)
+{
+ if (is_graph())
+ graph_trace_open(iter);
+}
+
+static void wakeup_trace_close(struct trace_iterator *iter)
+{
+ if (iter->private)
+ graph_trace_close(iter);
+}
+
+#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC)
+
+static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
+{
+ /*
+ * In graph mode call the graph tracer output function,
+ * otherwise go with the TRACE_FN event handler
+ */
+ if (is_graph())
+ return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
+
+ return TRACE_TYPE_UNHANDLED;
+}
+
+static void wakeup_print_header(struct seq_file *s)
+{
+ if (is_graph())
+ print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
+ else
+ trace_default_header(s);
+}
+
+static void
+__trace_function(struct trace_array *tr,
+ unsigned long ip, unsigned long parent_ip,
+ unsigned long flags, int pc)
+{
+ if (is_graph())
+ trace_graph_function(tr, ip, parent_ip, flags, pc);
+ else
+ trace_function(tr, ip, parent_ip, flags, pc);
+}
+#else
+#define __trace_function trace_function
+
+static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
+{
+ return -EINVAL;
+}
+
+static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
+{
+ return -1;
+}
+
+static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
+{
+ return TRACE_TYPE_UNHANDLED;
+}
+
+static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
+static void wakeup_print_header(struct seq_file *s) { }
+static void wakeup_trace_open(struct trace_iterator *iter) { }
+static void wakeup_trace_close(struct trace_iterator *iter) { }
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
/*
* Should this new latency be reported/recorded?
*/
@@ -152,7 +355,7 @@ probe_wakeup_sched_switch(void *ignore,
/* The task we are waiting for is waking up */
data = wakeup_trace->data[wakeup_cpu];

- trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
+ __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);

T0 = data->preempt_timestamp;
@@ -252,7 +455,7 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
* is not called by an assembly function (where as schedule is)
* it should be safe to use it here.
*/
- trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
+ __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);

out_locked:
arch_spin_unlock(&wakeup_lock);
@@ -303,12 +506,8 @@ static void start_wakeup_tracer(struct trace_array *tr)
*/
smp_wmb();

- register_ftrace_function(&trace_ops);
-
- if (tracing_is_enabled())
- tracer_enabled = 1;
- else
- tracer_enabled = 0;
+ if (start_func_tracer(is_graph()))
+ printk(KERN_ERR "failed to start wakeup tracer\n");

return;
fail_deprobe_wake_new:
@@ -320,7 +519,7 @@ fail_deprobe:
static void stop_wakeup_tracer(struct trace_array *tr)
{
tracer_enabled = 0;
- unregister_ftrace_function(&trace_ops);
+ stop_func_tracer(is_graph());
unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
unregister_trace_sched_wakeup(probe_wakeup, NULL);
@@ -379,9 +578,15 @@ static struct tracer wakeup_tracer __read_mostly =
.start = wakeup_tracer_start,
.stop = wakeup_tracer_stop,
.print_max = 1,
+ .print_header = wakeup_print_header,
+ .print_line = wakeup_print_line,
+ .flags = &tracer_flags,
+ .set_flag = wakeup_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
+ .open = wakeup_trace_open,
+ .close = wakeup_trace_close,
.use_max_tr = 1,
};

@@ -394,9 +599,15 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.stop = wakeup_tracer_stop,
.wait_pipe = poll_wait_pipe,
.print_max = 1,
+ .print_header = wakeup_print_header,
+ .print_line = wakeup_print_line,
+ .flags = &tracer_flags,
+ .set_flag = wakeup_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
+ .open = wakeup_trace_open,
+ .close = wakeup_trace_close,
.use_max_tr = 1,
};

--
1.7.1



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