Merge branch 'tracing/fastboot' into tracing/ftrace

include/linux/ftrace.h

@@ -234,6 +234,11 @@ ftrace_init_module(unsigned long *start, unsigned long *end) { }
 #endif
 
 
+/*
+ * Structure which defines the trace of an initcall.
+ * You don't have to fill the func field since it is
+ * only used internally by the tracer.
+ */
 struct boot_trace {
 	pid_t			caller;
 	char			func[KSYM_NAME_LEN];
@@ -244,13 +249,28 @@ struct boot_trace {
 };
 
 #ifdef CONFIG_BOOT_TRACER
+/* Append the trace on the ring-buffer */
 extern void trace_boot(struct boot_trace *it, initcall_t fn);
+
+/* Tells the tracer that smp_pre_initcall is finished.
+ * So we can start the tracing
+ */
 extern void start_boot_trace(void);
-extern void stop_boot_trace(void);
+
+/* Resume the tracing of other necessary events
+ * such as sched switches
+ */
+extern void enable_boot_trace(void);
+
+/* Suspend this tracing. Actually, only sched_switches tracing have
+ * to be suspended. Initcalls doesn't need it.)
+ */
+extern void disable_boot_trace(void);
 #else
 static inline void trace_boot(struct boot_trace *it, initcall_t fn) { }
 static inline void start_boot_trace(void) { }
-static inline void stop_boot_trace(void) { }
+static inline void enable_boot_trace(void) { }
+static inline void disable_boot_trace(void) { }
 #endif
 
 

init/main.c

@@ -711,6 +711,7 @@ int do_one_initcall(initcall_t fn)
 		it.caller = task_pid_nr(current);
 		printk("calling  %pF @ %i\n", fn, it.caller);
 		it.calltime = ktime_get();
+		enable_boot_trace();
 	}
 
 	it.result = fn();
@@ -722,6 +723,7 @@ int do_one_initcall(initcall_t fn)
 		printk("initcall %pF returned %d after %Ld usecs\n", fn,
 			it.result, it.duration);
 		trace_boot(&it, fn);
+		disable_boot_trace();
 	}
 
 	msgbuf[0] = 0;
@@ -882,7 +884,7 @@ static int __init kernel_init(void * unused)
 	 * we're essentially up and running. Get rid of the
 	 * initmem segments and start the user-mode stuff..
 	 */
-	stop_boot_trace();
+
 	init_post();
 	return 0;
 }

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);

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:

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

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);