trace-cmd: Always enabled tracing_enabled

The tracing_enabled file really needs to be deprecated. It should
not be used. But if the tracing_enabled file gets set to zero
somehow (by either the user or tool - latencytop?) then it will
disable output.

Since trace-cmd does not touch the file, it will confuse users
when they see no data recorded.

The simple answer is to always set tracing_enabled to one if the
file exists.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/trace-cmd.c b/trace-cmd.c
index d567ed8..4c17062 100644
--- a/trace-cmd.c
+++ b/trace-cmd.c
@@ -759,6 +759,28 @@ static void update_event(const char *name, const char *filter,
 
 }
 
+/*
+ * The debugfs file tracing_enabled needs to be deprecated.
+ * But just in case anyone fiddled with it. If it exists,
+ * make sure it is one.
+ * No error checking needed here.
+ */
+static void check_tracing_enabled(void)
+{
+        static int fd = -1;
+        char *path;
+
+        if (fd < 0) {
+                path = get_tracing_file("tracing_enabled");
+                fd = open(path, O_WRONLY);
+                put_tracing_file(path);
+
+                if (fd < 0)
+                        return;
+        }
+        write(fd, "1", 1);
+}
+
 static void write_tracing_on(int on)
 {
         static int fd = -1;
@@ -784,6 +806,8 @@ static void write_tracing_on(int on)
 
 static void enable_tracing(void)
 {
+        check_tracing_enabled();
+
         write_tracing_on(1);
 
         if (latency)