Merge branches 'tracing/blktrace', 'tracing/ftrace', 'tracing/urgent' and 'linus' into tracing/core

kernel/trace/Kconfig

@@ -164,9 +164,8 @@ config BOOT_TRACER
 	  representation of the delays during initcalls - but the raw
 	  /debug/tracing/trace text output is readable too.
 
-	  ( Note that tracing self tests can't be enabled if this tracer is
-	    selected, because the self-tests are an initcall as well and that
-	    would invalidate the boot trace. )
+	  You must pass in ftrace=initcall to the kernel command line
+	  to enable this on bootup.
 
 config TRACE_BRANCH_PROFILING
 	bool "Trace likely/unlikely profiler"
@@ -326,7 +325,7 @@ config FTRACE_SELFTEST
 
 config FTRACE_STARTUP_TEST
 	bool "Perform a startup test on ftrace"
-	depends on TRACING && DEBUG_KERNEL && !BOOT_TRACER
+	depends on TRACING && DEBUG_KERNEL
 	select FTRACE_SELFTEST
 	help
 	  This option performs a series of startup tests on ftrace. On bootup

kernel/trace/ftrace.c

@@ -1729,9 +1729,12 @@ static void clear_ftrace_pid(struct pid *pid)
 {
 	struct task_struct *p;
 
+	rcu_read_lock();
 	do_each_pid_task(pid, PIDTYPE_PID, p) {
 		clear_tsk_trace_trace(p);
 	} while_each_pid_task(pid, PIDTYPE_PID, p);
+	rcu_read_unlock();
+
 	put_pid(pid);
 }
 
@@ -1739,9 +1742,11 @@ static void set_ftrace_pid(struct pid *pid)
 {
 	struct task_struct *p;
 
+	rcu_read_lock();
 	do_each_pid_task(pid, PIDTYPE_PID, p) {
 		set_tsk_trace_trace(p);
 	} while_each_pid_task(pid, PIDTYPE_PID, p);
+	rcu_read_unlock();
 }
 
 static void clear_ftrace_pid_task(struct pid **pid)

kernel/trace/trace.c

@@ -53,6 +53,11 @@ unsigned long __read_mostly	tracing_thresh;
  */
 static bool __read_mostly tracing_selftest_running;
 
+/*
+ * If a tracer is running, we do not want to run SELFTEST.
+ */
+static bool __read_mostly tracing_selftest_disabled;
+
 /* For tracers that don't implement custom flags */
 static struct tracer_opt dummy_tracer_opt[] = {
 	{ }
@@ -110,14 +115,19 @@ static cpumask_var_t __read_mostly	tracing_buffer_mask;
  */
 int ftrace_dump_on_oops;
 
-static int tracing_set_tracer(char *buf);
+static int tracing_set_tracer(const char *buf);
+
+#define BOOTUP_TRACER_SIZE		100
+static char bootup_tracer_buf[BOOTUP_TRACER_SIZE] __initdata;
+static char *default_bootup_tracer;
 
 static int __init set_ftrace(char *str)
 {
-	tracing_set_tracer(str);
+	strncpy(bootup_tracer_buf, str, BOOTUP_TRACER_SIZE);
+	default_bootup_tracer = bootup_tracer_buf;
 	return 1;
 }
-__setup("ftrace", set_ftrace);
+__setup("ftrace=", set_ftrace);
 
 static int __init set_ftrace_dump_on_oops(char *str)
 {
@@ -469,7 +479,7 @@ int register_tracer(struct tracer *type)
 			type->flags->opts = dummy_tracer_opt;
 
 #ifdef CONFIG_FTRACE_STARTUP_TEST
-	if (type->selftest) {
+	if (type->selftest && !tracing_selftest_disabled) {
 		struct tracer *saved_tracer = current_trace;
 		struct trace_array *tr = &global_trace;
 		int i;
@@ -511,8 +521,25 @@ int register_tracer(struct tracer *type)
  out:
 	tracing_selftest_running = false;
 	mutex_unlock(&trace_types_lock);
-	lock_kernel();
 
+	if (!ret && default_bootup_tracer) {
+		if (!strncmp(default_bootup_tracer, type->name,
+			     BOOTUP_TRACER_SIZE)) {
+			printk(KERN_INFO "Starting tracer '%s'\n",
+			       type->name);
+			/* Do we want this tracer to start on bootup? */
+			tracing_set_tracer(type->name);
+			default_bootup_tracer = NULL;
+			/* disable other selftests, since this will break it. */
+			tracing_selftest_disabled = 1;
+#ifdef CONFIG_FTRACE_STARTUP_TEST
+			printk(KERN_INFO "Disabling FTRACE selftests due"
+			       " to running tracer '%s'\n", type->name);
+#endif
+		}
+	}
+
+	lock_kernel();
 	return ret;
 }
 
@@ -2166,7 +2193,7 @@ tracing_set_trace_read(struct file *filp, char __user *ubuf,
 	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 }
 
-static int tracing_set_tracer(char *buf)
+static int tracing_set_tracer(const char *buf)
 {
 	struct trace_array *tr = &global_trace;
 	struct tracer *t;
@@ -3061,12 +3088,9 @@ __init static int tracer_alloc_buffers(void)
 	trace_init_cmdlines();
 
 	register_tracer(&nop_trace);
+	current_trace = &nop_trace;
 #ifdef CONFIG_BOOT_TRACER
 	register_tracer(&boot_tracer);
-	current_trace = &boot_tracer;
-	current_trace->init(&global_trace);
-#else
-	current_trace = &nop_trace;
 #endif
 	/* All seems OK, enable tracing */
 	tracing_disabled = 0;
@@ -3084,5 +3108,26 @@ __init static int tracer_alloc_buffers(void)
 out:
 	return ret;
 }
+
+__init static int clear_boot_tracer(void)
+{
+	/*
+	 * The default tracer at boot buffer is an init section.
+	 * This function is called in lateinit. If we did not
+	 * find the boot tracer, then clear it out, to prevent
+	 * later registration from accessing the buffer that is
+	 * about to be freed.
+	 */
+	if (!default_bootup_tracer)
+		return 0;
+
+	printk(KERN_INFO "ftrace bootup tracer '%s' not registered.\n",
+	       default_bootup_tracer);
+	default_bootup_tracer = NULL;
+
+	return 0;
+}
+
 early_initcall(tracer_alloc_buffers);
 fs_initcall(tracer_init_debugfs);
+late_initcall(clear_boot_tracer);

kernel/trace/trace_boot.c

@@ -28,13 +28,13 @@ void start_boot_trace(void)
 
 void enable_boot_trace(void)
 {
-	if (pre_initcalls_finished)
+	if (boot_trace && pre_initcalls_finished)
 		tracing_start_sched_switch_record();
 }
 
 void disable_boot_trace(void)
 {
-	if (pre_initcalls_finished)
+	if (boot_trace && pre_initcalls_finished)
 		tracing_stop_sched_switch_record();
 }
 
@@ -43,6 +43,9 @@ static int boot_trace_init(struct trace_array *tr)
 	int cpu;
 	boot_trace = tr;
 
+	if (!tr)
+		return 0;
+
 	for_each_cpu(cpu, cpu_possible_mask)
 		tracing_reset(tr, cpu);
 
@@ -132,7 +135,7 @@ void trace_boot_call(struct boot_trace_call *bt, initcall_t fn)
 	unsigned long irq_flags;
 	struct trace_array *tr = boot_trace;
 
-	if (!pre_initcalls_finished)
+	if (!tr || !pre_initcalls_finished)
 		return;
 
 	/* Get its name now since this function could
@@ -164,7 +167,7 @@ void trace_boot_ret(struct boot_trace_ret *bt, initcall_t fn)
 	unsigned long irq_flags;
 	struct trace_array *tr = boot_trace;
 
-	if (!pre_initcalls_finished)
+	if (!tr || !pre_initcalls_finished)
 		return;
 
 	sprint_symbol(bt->func, (unsigned long)fn);