trace-cmd: Cache tracing_on file descriptor

Cache the tracing_on file descriptor to have the disable_tracing()
be able to shut down tracing without having to reopen the
tracing_on file.

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

1 files changed, 24 insertions, 21 deletions

diff --git a/trace-cmd.c b/trace-cmd.c
index 8839e74..a073017 100644
--- a/trace-cmd.c
+++ b/trace-cmd.c
@@ -459,34 +459,37 @@ static void disable_event(const char *name)
         fclose(fp);
 }
 
-static void enable_tracing(void)
+static void write_tracing_on(int on)
 {
-        FILE *fp;
+        static int fd = -1;
         char *path;
+        int ret;
 
-        /* reset the trace */
-        path = get_tracing_file("tracing_on");
-        fp = fopen(path, "w");
-        if (!fp)
-                die("writing to '%s'", path);
-        put_tracing_file(path);
-        fwrite("1", 1, 1, fp);
-        fclose(fp);
+        if (fd < 0) {
+                path = get_tracing_file("tracing_on");
+                fd = open(path, O_WRONLY);
+                if (fd < 0)
+                        die("opening '%s'", path);
+                put_tracing_file(path);
+        }
+
+        if (on)
+                ret = write(fd, "1", 1);
+        else
+                ret = write(fd, "0", 1);
+
+        if (ret < 0)
+                die("writing 'tracing_on'");
 }
 
-static void disable_tracing(void)
+static void enable_tracing(void)
 {
-        FILE *fp;
-        char *path;
+        write_tracing_on(1);
+}
 
-        /* reset the trace */
-        path = get_tracing_file("tracing_on");
-        fp = fopen(path, "w");
-        if (!fp)
-                die("writing to '%s'", path);
-        put_tracing_file(path);
-        fwrite("0", 1, 1, fp);
-        fclose(fp);
+static void disable_tracing(void)
+{
+        write_tracing_on(0);
 }
 
 static void disable_all(void)