tracing: Use str_has_prefix() in synth_event_create()

Since we now have a str_has_prefix() that returns the length, we can
use that instead of explicitly calculating it.

Link: http://lkml.kernel.org/r/03418373fd1e80030e7394b8e3e081c5de28a710.1549309756.git.tom.zanussi@linux.intel.com
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 66386ba1425f323af82d7e0fe5d3aedd3b4136bd..5b03b9a869bba07f1fb0b1a860e4c8dea26620a4 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1316,8 +1316,8 @@ static int synth_event_create(int argc, const char **argv)
 
        /* This interface accepts group name prefix */
        if (strchr(name, '/')) {
-               len = sizeof(SYNTH_SYSTEM "/") - 1;
-               if (strncmp(name, SYNTH_SYSTEM "/", len))
+               len = str_has_prefix(name, SYNTH_SYSTEM "/");
+               if (len == 0)
                        return -EINVAL;
                name += len;
        }