Merge branch 'tracing/fastboot' into tracing/ftrace

4 files changed, 41 insertions, 35 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d576dbd6def..29ab40a764c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3285,6 +3285,8 @@ __init static int tracer_alloc_buffers(void)
 
 	register_tracer(&nop_trace);
 #ifdef CONFIG_BOOT_TRACER
+	/* We don't want to launch sched_switch tracer yet */
+	global_trace.ctrl = 0;
 	register_tracer(&boot_tracer);
 	current_trace = &boot_tracer;
 	current_trace->init(&global_trace);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index bb547e933af..cc14a6bc109 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -49,6 +49,7 @@ struct ftrace_entry {
 	unsigned long		parent_ip;
 };
 extern struct tracer boot_tracer;
+extern struct tracer sched_switch_trace; /* Used by the boot tracer */
 
 /*
  * Context switch trace entry - which task (and prio) we switched from/to:
diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index d0a5e50eeff..bd5046c9deb 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -13,23 +13,33 @@
 #include "trace.h"
 
 static struct trace_array *boot_trace;
-static int trace_boot_enabled;
+static bool pre_initcalls_finished;
 
-
-/* Should be started after do_pre_smp_initcalls() in init/main.c */
+/* Tells the boot tracer that the pre_smp_initcalls are finished.
+ * So we are ready .
+ * It doesn't enable sched events tracing however.
+ * You have to call enable_boot_trace to do so.
+ */
 void start_boot_trace(void)
 {
-	trace_boot_enabled = 1;
+	pre_initcalls_finished = true;
 }
 
-void stop_boot_trace(void)
+void enable_boot_trace(void)
 {
-	trace_boot_enabled = 0;
+	if (pre_initcalls_finished)
+		tracing_start_cmdline_record();
 }
 
-void reset_boot_trace(struct trace_array *tr)
+void disable_boot_trace(void)
 {
-	stop_boot_trace();
+	if (pre_initcalls_finished)
+		tracing_stop_cmdline_record();
+}
+
+static void reset_boot_trace(struct trace_array *tr)
+{
+	sched_switch_trace.reset(tr);
 }
 
 static void boot_trace_init(struct trace_array *tr)
@@ -37,18 +47,18 @@ static void boot_trace_init(struct trace_array *tr)
 	int cpu;
 	boot_trace = tr;
 
-	trace_boot_enabled = 0;
-
 	for_each_cpu_mask(cpu, cpu_possible_map)
 		tracing_reset(tr, cpu);
+
+	sched_switch_trace.init(tr);
 }
 
 static void boot_trace_ctrl_update(struct trace_array *tr)
 {
 	if (tr->ctrl)
-		start_boot_trace();
+		enable_boot_trace();
 	else
-		stop_boot_trace();
+		disable_boot_trace();
 }
 
 static enum print_line_t initcall_print_line(struct trace_iterator *iter)
@@ -99,7 +109,7 @@ void trace_boot(struct boot_trace *it, initcall_t fn)
 	unsigned long irq_flags;
 	struct trace_array *tr = boot_trace;
 
-	if (!trace_boot_enabled)
+	if (!pre_initcalls_finished)
 		return;
 
 	/* Get its name now since this function could
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index b8f56beb1a6..888944d3409 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -16,7 +16,8 @@
 
 static struct trace_array	*ctx_trace;
 static int __read_mostly	tracer_enabled;
-static atomic_t			sched_ref;
+static int			sched_ref;
+static DEFINE_MUTEX(sched_register_mutex);
 
 static void
 probe_sched_switch(struct rq *__rq, struct task_struct *prev,
@@ -27,7 +28,7 @@ probe_sched_switch(struct rq *__rq, struct task_struct *prev,
 	int cpu;
 	int pc;
 
-	if (!atomic_read(&sched_ref))
+	if (!sched_ref)
 		return;
 
 	tracing_record_cmdline(prev);
@@ -123,20 +124,22 @@ static void tracing_sched_unregister(void)
 
 static void tracing_start_sched_switch(void)
 {
-	long ref;
-
-	ref = atomic_inc_return(&sched_ref);
-	if (ref == 1)
+	mutex_lock(&sched_register_mutex);
+	if (!(sched_ref++)) {
+		tracer_enabled = 1;
 		tracing_sched_register();
+	}
+	mutex_unlock(&sched_register_mutex);
 }
 
 static void tracing_stop_sched_switch(void)
 {
-	long ref;
-
-	ref = atomic_dec_and_test(&sched_ref);
-	if (ref)
+	mutex_lock(&sched_register_mutex);
+	if (!(--sched_ref)) {
 		tracing_sched_unregister();
+		tracer_enabled = 0;
+	}
+	mutex_unlock(&sched_register_mutex);
 }
 
 void tracing_start_cmdline_record(void)
@@ -153,12 +156,10 @@ static void start_sched_trace(struct trace_array *tr)
 {
 	sched_switch_reset(tr);
 	tracing_start_cmdline_record();
-	tracer_enabled = 1;
 }
 
 static void stop_sched_trace(struct trace_array *tr)
 {
-	tracer_enabled = 0;
 	tracing_stop_cmdline_record();
 }
 
@@ -172,7 +173,7 @@ static void sched_switch_trace_init(struct trace_array *tr)
 
 static void sched_switch_trace_reset(struct trace_array *tr)
 {
-	if (tr->ctrl)
+	if (tr->ctrl && sched_ref)
 		stop_sched_trace(tr);
 }
 
@@ -185,7 +186,7 @@ static void sched_switch_trace_ctrl_update(struct trace_array *tr)
 		stop_sched_trace(tr);
 }
 
-static struct tracer sched_switch_trace __read_mostly =
+struct tracer sched_switch_trace __read_mostly =
 {
 	.name		= "sched_switch",
 	.init		= sched_switch_trace_init,
@@ -198,14 +199,6 @@ static struct tracer sched_switch_trace __read_mostly =
 
 __init static int init_sched_switch_trace(void)
 {
-	int ret = 0;
-
-	if (atomic_read(&sched_ref))
-		ret = tracing_sched_register();
-	if (ret) {
-		pr_info("error registering scheduler trace\n");
-		return ret;
-	}
 	return register_tracer(&sched_switch_trace);
 }
 device_initcall(init_sched_switch_trace);