4 files changed, 70 insertions, 18 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index dde1d46f77e5..28f2644484d9 100644
--- a/kernel/trace/Kconfig
+++ b/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
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7e9a20b69939..68610031780b 100644
--- a/kernel/trace/ftrace.c
+++ b/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)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 152d0969adf8..bbdfaa2cbdb9 100644
--- a/kernel/trace/trace.c
+++ b/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 @@ out_free_buffer_mask:
 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);
diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 0e94b3d091f7..1f07895977a0 100644
--- a/kernel/trace/trace_boot.c
+++ b/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);