tracing/events: Fix to check the simple_tsk_fn creation

Sashiko pointed that this sample code does not correctly handle the
failure of thread creation because kthread_run() can return -errno.

Check the simple_tsk_fn is correctly initialized (created) or not.

Link: https://lore.kernel.org/all/178165817322.269421.3992299509400184196.stgit@devnote2/
Link: https://sashiko.dev/#/patchset/178092865666.163648.10457567771536160909.stgit%40devnote2
Fixes: 9cfe06f8cd5c ("tracing/events: add trace-events-sample")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c
index ecc7db237f2eff15054b4b237f14fcdc392d9e1b..0b7a6efdb247a8aef207f22ef3cb6a2de6283d0e 100644 (file)
--- a/samples/trace_events/trace-events-sample.c
+++ b/samples/trace_events/trace-events-sample.c
@@ -107,6 +107,10 @@ int foo_bar_reg(void)
         * for consistency sake, we still take the thread_mutex.
         */
        simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
+       if (IS_ERR_OR_NULL(simple_tsk_fn)) {
+               pr_err("Failed to create simple_thread_fn\n");
+               simple_tsk_fn = NULL;
+       }
  out:
        mutex_unlock(&thread_mutex);
        return 0;