1 files changed, 54 insertions, 6 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2f8ac1f008f5..2c720c79bc60 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)
 {
@@ -468,7 +478,7 @@ 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;
@@ -510,8 +520,25 @@ 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;
 }
 
@@ -2245,7 +2272,7 @@ 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;
@@ -3163,5 +3190,26 @@ 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);