ftrace: force recording

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 55 insertions, 0 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index a42390c1d6e1..2c1670c65236 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -54,6 +54,8 @@ struct dyn_ftrace {
         unsigned long     flags;
 };
 
+int ftrace_force_update(void);
+
 /* defined in arch */
 extern int ftrace_ip_converted(unsigned long ip);
 extern unsigned char *ftrace_nop_replace(void);
@@ -66,6 +68,8 @@ extern int ftrace_update_ftrace_func(ftrace_func_t func);
 extern void ftrace_caller(void);
 extern void ftrace_call(void);
 extern void mcount_call(void);
+#else
+# define ftrace_force_update() do { } while (0)
 #endif
 
 static inline void tracer_disable(void)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 97d5cb7b7e75..4facf5ceeb86 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -146,6 +146,10 @@ static int notrace __unregister_ftrace_function(struct ftrace_ops *ops)
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 
+static struct task_struct *ftraced_task;
+static DECLARE_WAIT_QUEUE_HEAD(ftraced_waiters);
+static unsigned long ftraced_iteration_counter;
+
 enum {
         FTRACE_ENABLE_CALLS             = (1 << 0),
         FTRACE_DISABLE_CALLS            = (1 << 1),
@@ -590,9 +594,12 @@ static int notrace ftraced(void *ignore)
                         ftraced_trigger = 0;
                         ftrace_record_suspend--;
                 }
+                ftraced_iteration_counter++;
                 mutex_unlock(&ftraced_lock);
                 mutex_unlock(&ftrace_sysctl_lock);
 
+                wake_up_interruptible(&ftraced_waiters);
+
                 ftrace_shutdown_replenish();
 
                 set_current_state(TASK_INTERRUPTIBLE);
@@ -1050,6 +1057,49 @@ static struct file_operations ftrace_filter_fops = {
         .release = ftrace_filter_release,
 };
 
+/**
+ * ftrace_force_update - force an update to all recording ftrace functions
+ *
+ * The ftrace dynamic update daemon only wakes up once a second.
+ * There may be cases where an update needs to be done immediately
+ * for tests or internal kernel tracing to begin. This function
+ * wakes the daemon to do an update and will not return until the
+ * update is complete.
+ */
+int ftrace_force_update(void)
+{
+        unsigned long last_counter;
+        DECLARE_WAITQUEUE(wait, current);
+        int ret = 0;
+
+        if (!ftraced_task)
+                return -ENODEV;
+
+        mutex_lock(&ftraced_lock);
+        last_counter = ftraced_iteration_counter;
+
+        set_current_state(TASK_INTERRUPTIBLE);
+        add_wait_queue(&ftraced_waiters, &wait);
+
+        do {
+                mutex_unlock(&ftraced_lock);
+                wake_up_process(ftraced_task);
+                schedule();
+                mutex_lock(&ftraced_lock);
+                if (signal_pending(current)) {
+                        ret = -EINTR;
+                        break;
+                }
+                set_current_state(TASK_INTERRUPTIBLE);
+        } while (last_counter == ftraced_iteration_counter);
+
+        mutex_unlock(&ftraced_lock);
+        remove_wait_queue(&ftraced_waiters, &wait);
+        set_current_state(TASK_RUNNING);
+
+        return ret;
+}
+
 static __init int ftrace_init_debugfs(void)
 {
         struct dentry *d_tracer;
@@ -1095,6 +1145,7 @@ static int __init notrace ftrace_dynamic_init(void)
                 return -1;
 
         last_ftrace_enabled = ftrace_enabled = 1;
+        ftraced_task = p;
 
         return 0;
 }